Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Yoichiro Kuninobu Last modified date:2019.08.06

Professor / Department of Fundamental Organic Chemistry / Institute for Materials Chemistry and Engineering


Papers
1. Xu Lu, Yusuke Yoshigoe, Haruka Ida, Mitsumi Nishi, Motomu Kanai, Yoichiro Kuninobu, Hydrogen Bond-Accelerated meta-Selective C-H Borylation of Aromatic Compounds and Expression of Functional Group and Substrate Specificities, ACS Catalysis, 10.1021/acscatal.8b05005, 9, 3, 1705-1709, 2019.03, We found that meta-selective C-H borylation of aromatic compounds was accelerated when using urea moiety-containing bipyridine-type ligands unlike in cases involving a bipyridine-type ligand without the urea moiety. The acceleration was due to the recognition and capture of the aromatic substrates by the urea moiety of the ligand by hydrogen bonding. The acceleration was further enhanced by modifying the electronic and steric properties of the ligand. The functional group and substrate specificities were also observed using the urea moiety-containing ligands..
2. Jie Wang, Takeru Torigoe, Yoichiro Kuninobu, Hydrogen-Bond-Controlled Formal Meta-Selective C-H Transformations and Regioselective Synthesis of Multisubstituted Aromatic Compounds, Organic Letters, 10.1021/acs.orglett.9b00030, 21, 5, 1342-1346, 2019.03, The meta-selective introduction of functional groups into aromatic substrates was successfully achieved by hydrogen-bond-controlled meta-selective C-H borylation and successive conversion of the boryl group to other functional groups. By this method a wide range of functional groups could be introduced without isolation of the borylated intermediates. The desired meta-functionalized aromatic products were obtained in a one-pot manner even on a gram scale. Regioselective synthesis of multisubstituted aromatic compounds was also achieved..
3. Takaya Togo, Youhei Sohma, Yoichiro Kuninobu, Motomu Kanai, Palladium-catalyzed C–H heteroarylation of 2,5-disubstituted imidazoles, Chemical and Pharmaceutical Bulletin, 10.1248/cpb.c18-00586, 196-198, 2019.01, We developed a palladium-catalyzed C–H N-heteroarylation of N-protected-2,5-disubstituted imidazoles at the C4-position using N-heteroaryl halides as a coupling partner. Intensive reaction condition screening led us to identify fluo-rinated bathophenanthroline 7 as the optimum ligand for the palladium catalyst. This reaction will enhance lead optimization of drug candidates by facilitating the synthesis of hetero-biaryl compounds containing an imidazole ring..
4. Yoichiro Kuninobu, Masaki Yamamoto, Mitsumi Nishi, Tomoyuki Yamamoto, Takashi Matsuki, Masahito Murai, Kazuhiko Takai, Rhenium-catalyzed ortho-alkylation of phenols, Organic Syntheses, 10.1002/0471264229.os094.20, 94, 2018.06, A procedure yielding pure 2-(1-methylnonyl)phenol (1) as a colorless oil is presented. An oven-dried Schlenk flask with a Teflon-coated magnetic stir bar and a reflux condenser with a three-way stopcock is primarily used as paraphernalia. A discussion on ortho-monoalkylated phenol derivatives as important bioactive compounds and functional materials concludes the chapter..
5. Jizhi Ni, Atsuhiko Taniguchi, Shuta Ozawa, Yukiko Hori, Yoichiro Kuninobu, Takashi Saito, Takaomi C. Saido, Taisuke Tomita, Youhei Sohma, Motomu Kanai, Near-Infrared Photoactivatable Oxygenation Catalysts of Amyloid Peptide, Chem, 10.1016/j.chempr.2018.02.008, 4, 4, 807-820, 2018.04, Toxic aggregation of amyloid peptide and protein is intimately related to a number of human diseases, including Alzheimer's disease (AD). Here, we developed biocompatible photooxygenation catalyst 9, which can selectively oxygenate and degrade the pathogenic aggregation of AD-related amyloid-β peptide (Aβ) under near-infrared (NIR) light irradiation. On the basis of the structure of a fluorescent Aβ probe, CRANAD-2, a bromine atom was introduced to increase the production of singlet oxygen for photooxygenation. The use of julolidine and perfluoroalkylborate moieties as electron-donor and -acceptor components, respectively, markedly enhanced the photocatalytic activity and reduced phototoxicity. Photooxygenation of aggregated Aβ by 9 under NIR irradiation in the presence of cells attenuated the cytotoxicity of Aβ. The tissue permeability of NIR enabled catalytic photooxygenation of aggregated Aβ under the mouse skin. Moreover, injection of the catalyst to the AD-model mouse brain along with NIR light irradiation led to a significant decrease in the intact Aβ level in the brain. An artificial chemical catalysis that can selectively transform toxic aggregates of peptides and proteins to non-toxic species under physiologic conditions would find therapeutic applications to treat currently- incurable amyloid diseases. Because peptide and protein aggregation generally depends on intermolecular hydrophobic interactions, covalent installation of hydrophilic oxygen atoms from aerobic oxygen to a peptide or protein (i.e., oxygenation) would decrease the aggregative property. Here, we report a biocompatible photooxygenation catalyst that can selectively oxygenate and degrade the pathogenic aggregation of the peptide responsible for Alzheimer's disease (AD) under near-infrared light irradiation. The detoxicating chemical catalysis targeting aggregated amyloid-β peptide proceeded in the AD-model mouse brain. The results obtained in this study are an important step toward using artificial catalysis as a potential therapeutic strategy against amyloid diseases. A biocompatible photooxygenation catalyst that can selectively oxygenate and degrade the pathogenic aggregation of Alzheimer's disease (AD)-related amyloid-β peptide (Aβ) under near-infrared light irradiation has been developed. The catalyst oxygenates Aβ embedded under the skin of a living mouse and diminishes the intact Aβ level in an AD-model mouse brain. The new catalyst is potentially applicable for the treatment of peripheral amyloid diseases and AD..
6. Takayuki Wakaki, Takaya Togo, Daisuke Yoshidome, Yoichiro Kuninobu, Motomu Kanai, Palladium-catalyzed synthesis of diaryl ketones from aldehydes and (hetero)aryl halides via C-H bond activation, ACS Catalysis, 10.1021/acscatal.8b00440, 8, 4, 3123-3128, 2018.04, We developed a palladium-catalyzed C-H transformation that enabled the synthesis of ketones from aldehydes and (hetero)aryl halides. The use of picolinamide ligands was key to achieving the transformation. Heteroaryl ketones, as well as diaryl ketones, were synthesized in good to excellent yields, even in gram-scale, using this reaction. Results of density functional theory (DFT) calculations support the C-H bond activation pathway..
7. Takahiro Shirai, Motomu Kanai, Yoichiro Kuninobu, 2-Position-Selective C-H Perfluoroalkylation of Quinoline Derivatives, Organic Letters, 10.1021/acs.orglett.8b00339, 20, 6, 1593-1596, 2018.03, We developed 2-position-selective, direct C-H trifluoromethylation, pentafluoroethylation, and heptafluoropropylation of quinoline derivatives. Regioselective transformation was achieved without derivatization of the quinolines. The reaction proceeded at room temperature with high functional group tolerance, even in gram scale. Notably, the reaction was applicable to substrates containing a functional group sensitive to oxidation and a drug molecule..
8. Takeshi Yamakawa, Yusuke Yoshigoe, Zijia Wang, Motomu Kanai, Yoichiro Kuninobu, Preparation of solid-state luminescent materials by complexation between π-conjugated molecules and activators, Chemistry Letters, 10.1246/cl.180735, 47, 11, 1391-1394, 2018.01, A combination of simple π-conjugated molecules bearing a lone pair on heteroatom(s) and activators afforded new solidstate fluorescent materials. A solid-state red-emitting material that exhibits aggregation-induced emission was also synthesized by the present method..
9. Yoichiro Kuninobu, Development of Novel C-H Bond Transformations and Their Application to the Synthesis of Organic Functional Molecules, Synlett, 10.1055/s-0037-1610531, 29, 16, 2093-2107, 2018.01, This personal account summarizes our recent progress in the development of C-H transformations. We achieved ortho -selective C-H borylations and silylations by using Lewis acid-base interaction between two substrates and we achieved meta - and ortho -selective C-H borylations by using hydrogen bonding or Lewis acid-base interaction between a hydrogen donor or Lewis acid unit of a ligand and a functional group of a substrate. Regioselective C-H trifluoromethylations and related reactions of six-membered heteroaromatic compounds were realized at their 2- and 4-positions and at their benzylic positions. In addition, we developed C-H transformations directed towards the synthesis of organic functional materials, such as highly soluble polyimides or π-conjugated molecules containing either heteroatom(s) or a Lewis acid-base interaction. 1 Introduction 2 Regioselective C-H Transformations Controlled by Noncovalent Bond Interactions 2.1 Regioselective C-H Transformations Controlled by Lewis Acid-Base Interaction between Two Substrates 2.2 Regioselective C-H Transformation Controlled by Hydrogen Bonding between Ligand and Substrate 2.3 Regioselective C-H Transformations Controlled by Lewis Acid-Base Interactions between Ligands and Substrates 3 Trifluoromethylation and Related Transformations of Six-Membered Heteroaromatic Compounds 3.1 2-Position-Selective C-H Trifluoromethylation of Six-Membered Heteroaromatic Compounds 3.2 4-Position-Selective C-H Trifluoromethylation of Six-Membered Heteroaromatic Compounds 3.3 Benzyl Position-Selective C-H Trifluoromethylation of Six-Membered Heteroaromatic Compounds 4 C-H Transformations Leading to the Synthesis of Organic Functional Materials 4.1 Heteroatom-Containing π-Conjugated Molecules 4.2 π-Conjugated Molecules Containing a Lewis Acid-Base Interaction 4.3 Soluble Polyimide Derivatives 5 Conclusions..
10. Takeshi Yamakawa, Yusuke Yoshigoe, Zijia Wang, Motomu Kanai, Yoichiro Kuninobu, Preparation of solid-state luminescent materials by complexation between π-conjugated molecules and activators, Chemistry Letters, 10.1246/cl.180735, 47, 11, 1391-1394, 2018.01, A combination of simple π-conjugated molecules bearing a lone pair on heteroatom(s) and activators afforded new solidstate fluorescent materials. A solid-state red-emitting material that exhibits aggregation-induced emission was also synthesized by the present method..
11. Hong Liang Li, Motomu Kanai, Yoichiro Kuninobu, Iridium/Bipyridine-Catalyzed ortho-Selective C-H Borylation of Phenol and Aniline Derivatives, Organic Letters, 10.1021/acs.orglett.7b02936, 19, 21, 5944-5947, 2017.11, An iridium-catalyzed ortho-selective C-H borylation of phenol and aniline derivatives has been successfully developed. Iridium/bipyridine-catalyzed C-H borylation generally occurred at the meta- and para-positions of aromatic substrates. Introduction of an electron-withdrawing substituent on the bipyridine-type ligand and a methylthiomethyl group on the hydroxy and amino groups of the phenol and aniline substrates, however, dramatically altered the regioselectivity, affording exclusively ortho-borylated products. The reaction proceeded in good to excellent yields with good functional group tolerance. C-H borylation was applied to the synthesis of a calcium receptor modulator..
12. Yoshigoe, Y.; Kuninobu, Y., Iron-Catalyzed ortho-Selective C−H Borylation of 2-Phenylpyridines and Their Analogs, Org. Lett. , 10.1021/acs.orglett.7b01423, 19, 13, 3450-3453, 2017.06.
13. Wang, Z.; Kanai, M.; Kuninobu, Y., Iron-Catalyzed Acyloxyalkylation of Styrenes Using Hypervalent Iodine Reagents, Org. Lett. , 10.1021/acs.orglett.7b00923, 19, 9, 2398-2401, 2017.04.
14. Li, H.-L.; Kuninobu, Y.; Kanai, M., Lewis Acid-Base Interaction-Controlled ortho-Selective C-H Borylation of Aryl Sulfides, Angew. Chem. Int. Ed. , 10.1002/anie.201610041, 56, 6, 1495-1499, 2017.02.
15. Masahiro Nagase, Yoichiro Kuninobu, Motomu Kanai, 4-Position-Selective C-H Perfluoroalkylation and Perfluoroarylation of Six-Membered Heteroaromatic Compounds, Journal of the American Chemical Society, 10.1021/jacs.6b01753, 138, 19, 6103-6106, 2016.05, The first 4-position-selective C-H perfluoroalkylation and perfluoroarylation of six-membered heteroaromatic compounds were achieved using nucleophilic perfluoroalkylation and perfluoroarylation reagents. The regioselectivity was controlled by electrophilically activating the heteroaromatic rings, while sterically hindering the 2-position, with a sterically bulky borane Lewis acid. The reaction proceeded in good yield, even in gram scale, and by a sequential reaction without isolating the intermediates. This reaction could be applied to late-stage trifluoromethylation of a bioactive compound..
16. Zijia Wang, Shunsuke Sueki, Motomu Kanai, Yoichiro Kuninobu, Rhenium-Catalyzed Synthesis of 1,3-Diiminoisoindolines via Insertion of Carbodiimides into a C-H Bond of Aromatic and Heteroaromatic Imidates, Organic Letters, 10.1021/acs.orglett.6b01012, 18, 10, 2459-2462, 2016.05, The rhenium-catalyzed synthesis of 1,3-diiminoisoindolines and their related compounds from aromatic or heteroaromatic imidates and carbodiimides are reported via C-H bond activation. This reaction is the first example of a transition-metal-catalyzed insertion of carbodiimides into an aromatic or heteroaromatic C-H bond and a novel method for synthesizing 1,3-diiminoisoindolines and their related compounds. Unsymmetrical 1,3-diiminoisoindolines were easily obtained using this method. The reaction proceeded in good to excellent yield using a variety of substrates..
17. Masahito Murai, Yutaro Takeuchi, Kanae Yamauchi, Yoichiro Kuninobu, Kazuhiko Takai, Rhodium-Catalyzed Synthesis of Chiral Spiro-9-silabifluorenes by Dehydrogenative Silylation
Mechanistic Insights into the Construction of Tetraorganosilicon Stereocenters, Chemistry - A European Journal, 10.1002/chem.201504718, 22, 17, 6048-6058, 2016.04, Mechanistic insight into the construction of quaternary silicon chiral centers by rhodium-catalyzed synthesis of spiro-9-silabifluorenes through dehydrogenative silylation is reported. The C2-symmetric bisphosphine ligand, BINAP, was effective in controlling enantioselectivity, and axially chiral spiro-9-silabifluorenes were obtained in excellent yields with high enantiomeric excess. Monitoring of the reaction revealed the presence of a monohydrosilane intermediate as a mixture of two constitutional isomers. The reaction proceeded through two consecutive dehydrogenative silylations, and the absolute configuration was determined in the first silylative cyclization. Competitive reactions with electron-rich and electron-deficient dihydrosilanes indicated that the rate of silylative cyclization increased with decreasing electron density on the silicon atom of the starting dihydrosilane. Further investigation disclosed a rare interconversion between the two constitutional isomers of the monohydrosilane intermediate with retention of the absolute configuration. Silicon-centered chirality: A combination of [{RhCl(cod)}2] (cod=1,5-cyclooctadiene) and chiral bisphosphine ligand, (R)-BINAP, catalyzes the asymmetric induction of axial chirality through two consecutive dehydrogenative silylations of unactivated C(sp2)-H bonds (see scheme). A mechanistic investigation revealed that the absolute configuration is determined in the first dehydrogenative silylation, and this reaction may involve a rare example of C-Si bond cleavage with retention of the silicon-centered chirality..
18. Yoichiro Kuninobu, Kanae Yamauchi, Naoya Tamura, Takayuki Seiki, Kazuhiko Takai, Erratum
Rhodium-catalyzed asymmetric synthesis of spirosilabifluorene derivatives (Angewandte Chemie - International Edition (2013) (52) DOI: 10.1002/anie.201207723), Angewandte Chemie - International Edition, 10.1002/anie.201511117, 55, 6, 1948, 2016.02.
19. Yoichiro Kuninobu, Mitsumi Nishi, Motomu Kanai, 5-Position-selective C-H trifluoromethylation of 8-aminoquinoline derivatives, Organic and Biomolecular Chemistry, 10.1039/c6ob01325b, 14, 34, 8092-8100, 2016.01, We developed a copper-catalyzed 5-position-selective C-H trifluoromethylation of 8-aminoquinoline derivatives. The reaction proceeded with high functional group tolerance under mild conditions. In the case of quinolines with an amide, carbamate, urea, or sulfonamide group at the 8-position of quinoline moieties, a radical scavenger experiment indicated that the reaction proceeded via a radical pathway. The protecting group of an 8-amidoquinoline derivative could be removed by hydrolysis. On the other hand, the trifluoromethylation of 8-aminoquinolines was also promoted by other Lewis acids as well as a copper catalyst and proceeded even in the presence of a radical scavenger. These results indicated that the trifluoromethylation of 8-aminoquinolines proceeded via a Friedel-Crafts-type reaction. Interestingly, the copper salt works as either a catalyst for the formation of a CF3 radical or a Lewis acid to promote a Friedel-Crafts-type reaction, depending on the substrate..
20. Shunsuke Sueki, Zijia Wang, Yoichiro Kuninobu, Manganese- and Borane-Mediated Synthesis of Isobenzofuranones from Aromatic Esters and Oxiranes via C-H Bond Activation, Organic Letters, 10.1021/acs.orglett.5b03474, 18, 2, 304-307, 2016.01, A manganese- and borane-mediated synthesis of isobenzofuranones from esters and oxiranes is developed. The reaction proceeded at aromatic, heteroaromatic, and olefinic C-H bonds with high functional group tolerance. This is the first example of a manganese-catalyzed C-H transformation using an oxygen-directing group. Triphenylborane played an important role in this reaction to cooperatively promote the annulation reaction. Kinetic isotope effect experiments revealed that C-H bond activation of the aromatic rings was the rate-determining step..
21. Yoichiro Kuninobu, The development of novel C-H bond transformations and their application to the synthesis of organic functional molecules, Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry, 10.5059/yukigoseikyokaishi.74.1058, 74, 11, 1058-1068, 2016.01, This personal account summarizes our recent progress in the development of C-H transformations. We achieved ortho -selective C-H borylation and silylation using Lewis acid-base interaction between two substrates, and meta -selective C-H borylation using hydrogen bonding between a hydrogen donor unit of a ligand and a substrate functional group. Regioselective C-H trifluoromethylation and related reactions of 6-membered heteroaromatic compounds were realized at the 2-, 4-, and benzylic-positions of the heteroaromatic rings. In addition, we developed C-H transformations directed towards the synthesis of organic functional materials, such as highly soluble polyimides and π-conjugated molecules containing either heteroatom(s) or a Lewis acid-base interaction..
22. Yoichiro Kuninobu, Shunsuke Sueki, C-H Bond Transformations Leading to the Synthesis of Organic Functional Materials, Synthesis (Germany), 10.1055/s-0035-1560346, 47, 24, 3823-3845, 2015.12, In this review, transition-metal-catalyzed or -mediated C-H transformations leading to the synthesis of organic functional materials, such as oligomers, polymers, and π-conjugated molecules, are summarized. 1 Introduction 2 Oligomers and Polymers 2.1 Synthesis of Oligomers and Polymers 2.2 Chemical Modification of Polymers 3 π-Conjugated Molecules 3.1 Indenes and Fluorenes 3.2 Acenes 3.3 Triphenylenes 3.4 Chemical Modification of Perylene Diimides 3.5 Nanographenes 3.6 Condensed Polycyclic π-Conjugated Molecules with Five-Membered Heteroaromatic Rings 3.7 π-Conjugated Molecules with Nitrogen-Containing Six-Membered Heteroaromatics 3.8 Porphyrins 3.9 Miscellaneous (π-Conjugated Molecules) 4 Miscellaneous (Excluding Polymers and π-Conjugated Molecules) 5 Outlook and Conclusions..
23. Yoichiro Kuninobu, Haruka Ida, Mitsumi Nishi, Motomu Kanai, A meta-selective C-H borylation directed by a secondary interaction between ligand and substrate, Nature Chemistry, 10.1038/nchem.2322, 7, 9, 712-717, 2015.09, Regioselective C-H bond transformations are potentially the most efficient method for the synthesis of organic molecules. However, the presence of many C-H bonds in organic molecules and the high activation barrier for these reactions make these transformations difficult. Directing groups in the reaction substrate are often used to control regioselectivity, which has been especially successful for the ortho-selective functionalization of aromatic substrates. Here, we describe an iridium-catalysed meta-selective C-H borylation of aromatic compounds using a newly designed catalytic system. The bipyridine-derived ligand that binds iridium contains a pendant urea moiety. A secondary interaction between this urea and a hydrogen-bond acceptor in the substrate places the iridium in close proximity to the meta-C-H bond and thus controls the regioselectivity. 1 H NMR studies and control experiments support the participation of hydrogen bonds in inducing regioselectivity. Reversible direction of the catalyst through hydrogen bonds is a versatile concept for regioselective C-H transformations..
24. Yoichiro Kuninobu, Masahiro Nagase, Motomu Kanai, Benzylic C(sp3)-H Perfluoroalkylation of Six-Membered Heteroaromatic Compounds, Angewandte Chemie - International Edition, 10.1002/anie.201505335, 54, 35, 10263-10266, 2015.08, Successful benzylic C(sp3)-H trifluoromethylation, pentafluoroethylation, and heptafluoropropylation of six-membered heteroaromatic compounds were achieved as the first examples of a practical benzylic C(sp3)-H perfluoroalkylation. In these reactions, BF2CnF2n+1 (n=1-3) functioned as both a Lewis acid to activate the benzylic position and a CnF2n+1 (n=1-3) source. The perfluoroalkylation proceeded at both terminal and internal positions of the alkyl chains. Perfluoroalkylated products were obtained in moderate to excellent yields, even on gram scale, and in a sequential procedure without isolation of the intermediates. By using this method, trifluoromethylation of a bioactive compound, as well as introduction of a CF3 group into a bioactive molecular skeleton, proceeded regioselectively..
25. Masahito Murai, Hirotaka Takeshima, Haruka Morita, Yoichiro Kuninobu, Kazuhiko Takai, Acceleration effects of phosphine ligands on the rhodium-catalyzed dehydrogenative silylation and germylation of unactivated C(sp3)-H bonds, Journal of Organic Chemistry, 10.1021/acs.joc.5b00920, 80, 11, 5407-5414, 2015.06, The current work describes the marked rate of acceleration caused by phosphine ligands on the rhodium-catalyzed dehydrogenative silylation and germylation of unactivated C(sp3)-H bonds. The reactivity was affected by the steric and electronic nature of the phosphine ligands. The use of the bulky and electron-rich diphosphine ligand (R)-DTBM-SEGPHOS was highly effective to yield the dehydrogenative silylation products selectively in the presence of a hydrogen acceptor. An appropriate choice of C2-symmetric chiral diphosphine ligand enables the asymmetric dehydrogenative silylation via the enantioselective desymmetrization of the C(sp3)-H bond. The unprecedented catalytic germylation of C(sp3)-H bonds with dehydrogenation was also examined with the combination of the rhodium complex and a wide bite angle diphosphine ligand to provide the corresponding 2,3-dihydrobenzo[b]germoles in good yield..
26. Kenta Saito, Prasanna Kumara Chikkade, Motomu Kanai, Yoichiro Kuninobu, Palladium-catalyzed construction of heteroatom-containing π-conjugated systems by intramolecular oxidative C-H/C-H coupling reaction, Chemistry - A European Journal, 10.1002/chem.201501116, 21, 23, 8365-8368, 2015.06, Synthesis of heteroatom-containing ladder-type π-conjugated molecules was successfully achieved via a palladium-catalyzed intramolecular oxidative C-H/C-H cross-coupling reaction. This reaction provides a variety of π-conjugated molecules bearing heteroatoms, such as nitrogen, oxygen, phosphorus, and sulfur atoms, and a carbonyl group. The π-conjugated molecules were synthesized efficiently, even in gram scale, and larger π-conjugated molecules were also obtained by a double C-H/C-H cross-coupling reaction and successive oxidative cycloaromatization..
27. Prasanna Kumara Chikkade, Yoichiro Kuninobu, Motomu Kanai, Copper-catalyzed intermolecular C(sp3)-H bond functionalization towards the synthesis of tertiary carbamates, Chemical Science, 10.1039/c5sc00238a, 6, 5, 3195-3200, 2015.05, We describe the development of an intermolecular unactivated C(sp3)-H bond functionalization towards the direct synthesis of tertiary carbamates. The transformation proceeded using a readily available, abundant first-row transition metal catalyst (copper), and isocyanates as the source of the amide moiety. This is a novel strategy for direct transformation of a variety of unactivated hydrocarbon feedstocks to N-alkyl-N-aryl and N,N-dialkyl carbamates without pre-functionalization or installation of a directing group. The reaction had a broad substrate scope with 3° > 2° > 1° site selectivity. The reaction proceeded even on a gram scale, and a corresponding free amine was directly obtained when the reaction was performed at high temperature. Kinetic studies suggested that radical-mediated C(sp3)-H bond cleavage was the rate-determining step..
28. Zhen Wang, Yoichiro Kuninobu, Motomu Kanai, Palladium-catalyzed oxirane-opening reaction with arenes via C-H bond activation, Journal of the American Chemical Society, 10.1021/jacs.5b02435, 137, 19, 6140-6143, 2015.05, We achieved a palladium-catalyzed C-H activation/C-C coupling reaction between arenes with a pyridyl, aminoquinolinyl, imino, or amide directing group, and oxiranes. The reaction proceeded at room temperature without any additives and tolerated a wide variety of functional groups, and the products were obtained in good to excellent yields, even on gram scale. This is the first example of a transition-metal-catalyzed intermolecular direct coupling reaction between a C-H bond of aromatic compounds and a carbon atom of oxiranes via C-H bond activation. By using N-methoxybenzamide as a substrate, we obtained 3-substituted isochroman-1-ones in one pot. The coupling reaction proceeded with stereoretention. Kinetic isotope effect experiments suggested that C-H bond activation is the rate-determining step..
29. Shunsuke Sueki, Yoichiro Kuninobu, Rhodium-catalysed synthesis of multi-substituted silylindenes from aryl alkynes and hydrosilanes via C-H bond activation, Chemical Communications, 10.1039/c5cc01569c, 51, 36, 7685-7688, 2015.05, We successfully developed rhodium-catalysed synthesis of multi-substituted silylindenes from 2 equivalents of aryl alkynes and 1 equivalent of hydrosilanes in moderate to good yields via C-H bond activation for the first time. The silyl groups of the obtained silylindenes could be converted to several other functional groups..
30. Takayuki Wakaki, Motomu Kanai, Yoichiro Kuninobu, Iridium-catalyzed ortho -selective C-H silylation of aromatic compounds directed toward the synthesis of π-conjugated molecules with Lewis acid-base interaction, Organic Letters, 10.1021/acs.orglett.5b00529, 17, 7, 1758-1761, 2015.04, We successfully developed an iridium-catalyzed ortho-selective C-H silylation of aromatic compounds. The reaction exhibited a wide substrate scope, and a variety of π-conjugated molecules were synthesized in good to excellent yields, even in gram scale. Several silyl groups could also be introduced into the products. The experimental results indicated that the regioselectivity could be controlled by a Lewis acid-base interaction between the Lewis acidic silicon atoms of fluorinated hydrosilanes and the Lewis basic nitrogen atoms of aromatic compounds..
31. Masahito Murai, Tetsuya Omura, Yoichiro Kuninobu, Kazuhiko Takai, Rhenium-catalysed dehydrogenative borylation of primary and secondary C(sp3)-H bonds adjacent to a nitrogen atom, Chemical Communications, 10.1039/c4cc09508a, 51, 22, 4583-4586, 2015.03, Rhenium-catalysed C(sp3)-H bond borylation in the absence of any oxidant, hydrogen acceptor, or external ligand, with the generation of H2 as the sole byproduct is described. The transformation, which represents a rare example of rhenium-catalysed C(sp3)-H bond functionalisation, features high atom efficiency and simple reaction conditions. This journal is.
32. Zhen Wang, Yoichiro Kuninobu, Motomu Kanai, Copper-mediated direct C(sp3)-H and C(sp2)-H acetoxylation, Organic Letters, 10.1021/ol5022542, 16, 18, 4790-4793, 2014.09, A copper-mediated terminal position-selective C-(sp3)-H acetoxylation using a bidentate directing group and AgOAc as an oxidant was achieved. This reaction has high functional group tolerance and is not affected by steric hindrance. The reaction proceeds in excellent yield, even in gram scale, and the directing group can be removed after the reaction. Aromatic C(sp2)-H acetoxylation also proceeded under similar reaction conditions..
33. Yutaka Matsuo, Yoichiro Kuninobu, Shingo Ito, Masaya Sawamura, Eiichi Nakamura, Friedel-Crafts functionalization of the cyclopentadienyl ligand in buckymetallocenes, Dalton Transactions, 10.1039/c3dt52002a, 43, 20, 7407-7412, 2014.05, Acylated buckyferrocene and ruthenocene, Fe(η5-C 60Me5)(η5-C5H4COR) (R = Me, Ph, and CHCHPh) and Ru(η5-C60Me 5)(η5-C5H4COR) (R = Me and Ph), were obtained by Friedel-Crafts acylation of the parent buckymetallocenes with the corresponding acid chlorides and aluminum chloride in carbon disulfide at ambient temperature. The electron withdrawing and sterically hindered nature of the acyl groups were revealed by X-ray crystallography, infrared spectroscopy and electrochemical measurements. The possibility of further derivatizing the acylated products was illustrated by the conversion of the acetyl buckyruthenocene into the corresponding hydroxy and acetoxy compounds Ru(η5-C60Me5)(η5-C 5H4CH(OH)Me) and Ru(η5-C 60Me5)(η5-C5H 4CH(OAc)Me). This journal is.
34. Noriaki Takemura, Yoichiro Kuninobu, Motomu Kanai, Copper-catalyzed benzylic C(sp3)-H alkoxylation of heterocyclic compounds, Organic and Biomolecular Chemistry, 10.1039/c4ob00215f, 12, 16, 2528-2532, 2014.04, We achieved intra- and intermolecular C(sp3)-H alkoxylation of benzylic positions of heteroaromatic compounds using CuBrn (n = 1, 2)/5,6-dimethylphenanthroline (or 4,7-dimethoxyphenanthroline) and ( tBuO)2 as a catalyst and an oxidant, respectively. The reaction proceeded at both terminal and internal benzylic positions of the alkyl groups. The intramolecular alkoxylation was performed on a gram scale. This journal is.
35. Kyalo Stephen Kanyiva, Yoichiro Kuninobu, Motomu Kanai, Palladium-catalyzed direct C-H silylation and germanylation of benzamides and carboxamides, Organic Letters, 10.1021/ol500519y, 16, 7, 1968-1971, 2014.04, A palladium-catalyzed regioselective activation of C(sp2)-H and C(sp3)-H bonds of benzamides and carboxamides, followed by coupling with disilanes to afford organosilanes in moderate to high yields, with the aid of 8-aminoquinoline as a directing group, is reported. Catalytic C(sp 2)-H germanylation of benzamides also proceeds under the same palladium catalysis. The reaction tolerates a wide variety of functional groups and is scalable without yield reduction. The bidentate directing group is readily removed and recovered by the reaction with a hydrazine, with concominant generation of an acyl hydrazide..
36. Zhen Wang, Jizhi Ni, Yoichiro Kuninobu, Motomu Kanai, Copper-catalyzed intramolecular C(sp3)-H and C(sp2)-H amidation by oxidative cyclization, Angewandte Chemie - International Edition, 10.1002/anie.201311105, 53, 13, 3496-3499, 2014.03, The first copper-catalyzed intramolecular C(sp3)-H and C(sp 2)-H oxidative amidation has been developed. Using a Cu(OAc) 2 catalyst and an Ag2CO3 oxidant in dichloroethane solvent, C(sp3)-H amidation proceeded at a terminal methyl group, as well as at the internal benzylic position of an alkyl chain. This reaction has a broad substrate scope, and various β-lactams were obtained in excellent yield, even on gram scale. Use of CuCl2 and Ag2CO3 under an O2 atmosphere in dimethyl sulfoxide, however, leads to 2-indolinone selectively by C(sp2)-H amidation. Kinetic isotope effect (KIE) studies indicated that C-H bond activation is the rate-determining step. The 5-methoxyquinolyl directing group could be removed by oxidation. Silver ox: By using a Cu(OAc)2 catalyst and an Ag2CO3 oxidant in dichloroethane solvent, C(sp3)-H amidation proceeded at a terminal methyl group as well as at the internal benzylic position of an alkyl chain. This reaction has a broad substrate scope, and various β-lactams were obtained in excellent yield, even on a gram scale. Use of CuCl2 and Ag2CO3 under an O2 atmosphere led to 2-indolinone selectively synthesized by C(sp2)-H amidation. DMSO=dimethylsulfoxide..
37. Qing Xiao, Xiangtai Meng, Motomu Kanai, Yoichiro Kuninobu, Palladium-catalyzed Ci-H fluorosilylation of 2-phenylpyridines
Synthesis of silafluorene equivalents, Angewandte Chemie - International Edition, 10.1002/anie.201310293, 53, 12, 3168-3172, 2014.03, Treatment of 2-phenylpyridines with amino(1,3,2-dioxaborolan-2-yl) diphenylsilane produced fluorosilylated 2-phenylpyridines in good to excellent yields under palladium catalysis. This reaction is the first example of Ci-H fluorosilylation. Single-crystal X-ray structure analysis revealed a Lewis acid-base interaction between the silicon and nitrogen atoms, and the obtained fluorosilylated products are silafluorene equivalents. The fluorosilylated products showed stronger fluorescence than the corresponding silafluorene derivative. Treatment of 2-phenylpyridines with amino(1,3,2-dioxaborolan-2-yl) diphenylsilane produced fluorosilylated 2-phenylpyridines in good to excellent yields under palladium catalysis. This reaction is the first example of Ci-H fluorosilylation. A Lewis acid-base interaction exists between the silicon and nitrogen atoms, and the obtained fluorosilylated products can be regarded as silafluorene equivalents..
38. Tomoaki Nishida, Haruka Ida, Yoichiro Kuninobu, Motomu Kanai, Regioselective trifluoromethylation of N-heteroaromatic compounds using trifluoromethyldifluoroborane activator, Nature communications, 10.1038/ncomms4387, 5, 2014.03, Many important drugs, agrochemicals and their lead compounds contain trifluoromethyl group(s). Most processes currently used to access trifluoromethyl group-containing molecules are performed by substitution of the carboxy or trichloromethyl groups using hazardous fluorinating reagents under harsh reaction conditions. Cross-coupling reactions between organohalides or boronic acids/esters and trifluoromethylating reagents are also used. Direct C-H trifluoromethylation of organic molecules, however, is the ideal method of introducing trifluoromethyl group(s). Despite the recent advances in C-H trifluoromethylation of N-heteroaromatic compounds, regioselective C-H trifluoromethylation of six-membered heteroaromatic compounds has yet to be achieved. Herein we present a general and reliable method for the synthesis of trifluoromethyl group-containing N-heteroaromatics through highly regioselective addition of a trifluoromethyl nucleophile to pyridine, quinoline, isoquinoline and two or three heteroatom-containing N-heteroaromatic N-oxides activated by trifluoromethyldifluoroborane. The C-H trifluoromethylation proceeds under mild conditions in gram scale with high functional group tolerance. This method will be useful in both laboratory and industrial processes..
39. Zhen Wang, Yoichiro Kuninobu, Motomu Kanai, Molybdenum-mediated desulfurization of dhiols and disulfides, Synlett, 10.1055/s-0034-1378315, 25, 13, 1869-1872, 2014.01, We have successfully achieved the molybdenum hexacarbonyl [Mo(CO) 6] mediated desulfurization of thiols and disulfides. In this reaction, the sulfhydryl (SH) mercapto groups of aryl, benzyl, primary and secondary alkyl thiols, and S-S single bonds of disulfides can be removed. This reaction has high functional group tolerance and is not affected by steric hindrance. The results of the reactions in acetone-d 6 suggest that the sources of hydrogen in the thiol and disulfide desulfurizations are the hydrogen atom(s) of a sulfhydryl group and acetone (solvent), respectively, and that the desulfurization proceeds via the formation of an organomolybdenum species..
40. Tomoaki Nishida, Aiko Fukazawa, Eriko Yamaguchi, Hiroya Oshima, Shigehiro Yamaguchi, Motomu Kanai, Yoichiro Kuninobu, Synthesis of pyridine N-oxide-BF2CF3 complexes and their fluorescence properties, Chemistry - An Asian Journal, 10.1002/asia.201301688, 9, 4, 1026-1030, 2014, Pyridine N-oxide-BF2CF3 and-BF2C 2F5 complexes and their derivatives were synthesized. Most of the complexes show fluorescence both in solution and in the solid state. By expanding the π-conjugated skeleton, the color of the fluorescence could be changed dramatically. A fluorophore with a high solvent dependency could also be produced. Since such compounds can be synthesized on a gram scale in high yield, and are stable to oxygen, water, and heat, the complexes hold great potential as organic functional materials. Too complex for simple answers: Complexes of pyridine N-oxide with BF2CF3 and BF 2C2F5, and their derivatives were synthesized. Most of the complexes fluoresce, both in solution and in the solid state. By expanding the π-conjugated skeleton, the color of the fluorescence could be changed dramatically. Owing to their properties such complexes hold potential as organic functional materials..
41. Shunsuke Sueki, Yuanfang Guo, Motomu Kanai, Yoichiro Kuninobu, Rhenium-catalyzed synthesis of 3-imino-1-isoindolinones by C-H bond activation
Application to the synthesis of polyimide derivatives, Angewandte Chemie - International Edition, 10.1002/anie.201306360, 52, 45, 11879-11883, 2013.11, Polyimide solution: Synthesis of the title compounds from aromatic imidates and isocyanates in good to excellent yields by a rhenium-catalyzed C-H bond transformation is described. The reaction also proceeded in high yield on gram scale and could be applied to the synthesis of polyimide derivatives (see figure), which are highly soluble in organic solvents..
42. Zhen Wang, Yoichiro Kuninobu, Motomu Kanai, Copper-catalyzed intramolecular N-S bond formation by oxidative dehydrogenative cyclization, Journal of Organic Chemistry, 10.1021/jo401056g, 78, 14, 7337-7342, 2013.07, Copper-catalyzed synthesis of benzo[d]isothiazol-3(2H)-ones and N-acyl-benzothiazetidine by intramolecular dehydrogenative cyclization is described. In this reaction, a new nitrogen-sulfur (N-S) bond is formed by N-H/S-H coupling. The present reaction has high functional group tolerance and gives products in gram scale. This method promotes double cyclization, allowing for synthesis of a drug intermediate..
43. Yoichiro Kuninobu, Transition metal-catalyzed highly efficient and novel transformations -Development of reactions using group 7 and other transition metal catalysts, Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry, 10.5059/yukigoseikyokaishi.71.425, 71, 5, 425-432, 2013.07, Rhenium and manganese-catalyzed regioselective insertion of unsaturated molecules into aromatic and olefinic C-H bonds have been achieved. In some cases, successive intramolecular nucleophilic cyclization proceeded. We have also succeeded in regioselective insertion of alkynes into a non-strained C-C single bond of 1,3-dicarbonyl compounds using a rhenium or manganese catalyst. In addition, we have succeeded in regio-and stereo-defined cycloaddition reactions. By using a rhodium or palladium catalyst, we have achieved direct and efficient carbon-heteroatom bond formations via C-H bond activation..
44. Shunsuke Sueki, Yoichiro Kuninobu, Copper-catalyzed N- and O-alkylation of amines and phenols using alkylborane reagents, Organic Letters, 10.1021/ol400323z, 15, 7, 1544-1547, 2013.04, By the reaction of amines with alkylborane reagents in the presence of a catalytic amount of copper(II) acetate Cu(OAc)2 and di-tert-butyl peroxide, a cross-coupling reaction proceeded and alkylated amines were obtained in good to excellent yields. Phenols are also applicable for this reaction, and the corresponding alkyl aryl ethers were produced..
45. Yoichiro Kuninobu, Takashi Iwanaga, Tetsuya Omura, Kazuhiko Takai, Palladium-catalyzed ortho-selective C-H borylation of 2-phenylpyridine and its derivatives at room temperature, Angewandte Chemie - International Edition, 10.1002/anie.201210328, 52, 16, 4431-4434, 2013.04, Boron delivery: C-H borylation at the ortho-position of aromatic compounds is promoted by the treatment of 2-phenylpyridine, or its derivatives, with 9-borabicyclo[3.3.1]nonane in the presence of a palladium catalyst. This reaction proceeds at room temperature and can be conducted without the palladium catalyst at higher temperatures. In both cases, the regioselectivity is controlled by Lewis acid-base interaction between the boron and nitrogen atoms..
46. Noriaki Takemura, Yoichiro Kuninobu, Motomu Kanai, Copper-catalyzed C-H alkoxylation of azoles, Organic Letters, 10.1021/ol303533z, 15, 4, 844-847, 2013.02, We achieved copper-catalyzed intramolecular and intermolecular alkoxylation of azoles. This reaction is a rare example of transition-metal-catalyzed C-H alkoxylation of heteroaromatic compounds. In addition, the alkoxylation reaction proceeded well even in gram scale. In most intermolecular alkoxylations, the use of an excess amount of alcohols (in some cases, alcohols are used as a solvent) is indispensable to efficiently promote the alkoxylation reaction, but this alkoxylation reaction proceeded using only 1 equiv of alcohols..
47. Yoichiro Kuninobu, Kanae Yamauchi, Naoya Tamura, Takayuki Seiki, Kazuhiko Takai, Rhodium-catalyzed asymmetric synthesis of spirosilabifluorene derivatives, Angewandte Chemie - International Edition, 10.1002/anie.201207723, 52, 5, 1520-1522, 2013.01, Si goes chiral: Treatment of a bis(biphenyl)silane with a catalytic amount of a rhodium complex gave a spirosilabifluorene bearing a quaternary silicon atom. By using a rhodium catalyst with a chiral phosphine ligand (see scheme), asymmetric dehydrogenative cyclization proceeded to give chiral derivatives in good yields and enantioselectivities..
48. Yoichiro Kuninobu, Takahiro Nakahara, Hirotaka Takeshima, Kazuhiko Takai, Rhodium-catalyzed intramolecular silylation of unactivated C(sp 3)-H bonds, Organic Letters, 10.1021/ol303353m, 15, 2, 426-428, 2013.01, The treatment of a variety of hydrosilanes, each incorporating a benzylic C(sp3)-H bond, with a rhodium catalyst resulted in intramolecular dehydrogenative silylation. This silylation reaction was found to occur at typically unreactive C(sp3)-H bonds located at terminal positions on alkyl chains. Interestingly, the rhodium catalyst also promoted regioselective silylation at a site internal to an alkyl chain..
49. Yoichiro Kuninobu, Kazuki Origuchi, Kazuhiko Takai, Palladium-catalyzed synthesis of a phosphine oxide with a chiral phosphorus center via C-H phosphination, Heterocycles, 10.3987/COM-12-12595, 85, 12, 3029-3034, 2012.12, A new phosphine oxide with a chiral phosphine center was synthesized from a bis(biphenyl)phosphine oxide by dehydrogenative intramolecular cyclization via P-H and C-H bond activation under palladium catalysis. The absolute configuration of one enantiomer of the phosphine oxide was determined by single crystal X-ray structure analysis. By reducing the phosphine oxide, the corresponding phosphine, which also has a chiral center, was produced. The phosphine compounds could be optically resolved by chiral HPLC column chromatography..
50. Mitsumi Nishi, Yoichiro Kuninobu, Kazuhiko Takai, Rhenium-catalyzed regio- and stereoselective synthesis of γ-thio-α,β-unsaturated ketones via insertion of terminal alkynes into the C-S bond, Organic Letters, 10.1021/ol302810u, 14, 23, 6116-6118, 2012.12, The reaction of α-thioketones and alkynes in the presence of a rhenium catalyst, [HRe(CO)4]n, gave γ-thio-α, β-unsaturated ketones in excellent yields. The alkynes were inserted into the carbon-sulfur bond of the α-thioketones, and isomerization of a double bond provided the products with high regio- and stereoselectivities. This reaction also proceeded in an intramolecular fashion..
51. Yoichiro Kuninobu, Takuya Yoshida, Kazuhiko Takai, Erratum
Correction to palladium-catalyzed synthesis of dibenzophosphole oxides via intramolecular dehydrogenative cyclization (Journal of Organic Chemistry (2011) 76 (7370-7376) DOI: 10.1021/jo201030j)), Journal of Organic Chemistry, 10.1021/jo3021506, 77, 20, 2012.10.
52. Yoichiro Kuninobu, Kazuhiko Takai, Development of novel and highly efficient methods to construct carboncarbon bonds using group 7 transition-metal catalysts, Bulletin of the Chemical Society of Japan, 10.1246/bcsj.20120015, 85, 6, 656-671, 2012.07, Rhenium-or manganese-catalyzed transformations based on the cleavage of inactive bonds, such as carbonhydrogen and carboncarbon bonds are discussed. Such transformations are recognized as key methods to realize efficient and powerful reactions. We also reveal novel regio- and/or stereodefined cycloaddition reactions using a rhenium or manganese catalyst. Most of the catalytic activities are typical of rhenium and manganese carbonyl complexes..
53. Shun Ichi Yamamoto, Kana Okamoto, Makiko Murakoso, Yoichiro Kuninobu, Kazuhiko Takai, Rhenium-catalyzed regioselective synthesis of multisubstituted pyridines from β-enamino ketones and alkynes via C-C bond cleavage, Organic Letters, 10.1021/ol301273j, 14, 12, 3182-3185, 2012.06, A new method is described for the regioselective synthesis of multisubstituted pyridine derivatives. Treatment of N-acetyl β-enamino ketones with alkynes in the presence of the rhenium catalyst, Re 2(CO) 10, gives multisubstituted pyridines regioselectively. In this reaction, the N-acetyl moieties are important for the selective formation of the multisubstituted pyridines. This reaction proceeds via insertion of alkynes into a carbon-carbon single bond of β-enamino ketones, intramolecular nucleophilic cyclization, and elimination of acetic acid..
54. Yoichiro Kuninobu, Tadamasa Uesugi, Atsushi Kawata, Kazuhiko Takai, Manganese-catalyzed cleavage of a carbon-carbon single bond between carbonyl carbon and α-carbon atoms of ketones, Angewandte Chemie - International Edition, 10.1002/anie.201104704, 50, 44, 10406-10408, 2011.10, Singled out: Treatment of ketones with carbodiimides in the presence of a catalytic amount of either [{HMn(CO)4}3] or [Mn 2(CO)10] gave amides in good to excellent yields. In this reaction, the carbon-carbon single bond of a ketone is cleaved efficiently. The reaction also proceeded by using isocyanates instead of carbodiimides..
55. Yoichiro Kuninobu, Kazuhiro Ohta, Kazuhiko Takai, Rhenium-catalyzed allylation of C-H bonds of benzoic and acrylic acids, Chemical Communications, 10.1039/c1cc12359a, 47, 38, 10791-10793, 2011.10, We have succeeded in the allylation of aromatic and olefinic C-H bonds of benzoic and acrylic acids using a rhenium catalyst, Re2(CO) 10. In this reaction, isomerization of the introduced allyl group to the 1-propenyl group did not occur..
56. Yuta Nishina, Tomohiro Tatsuzaki, Ayano Tsubakihara, Yoichiro Kuninobu, Kazuhiko Takai, Synthesis of multisubstituted cyclopentadienes from cyclopentenones prepared via catalytic double aldol condensation and nazarov reaction sequence, Synlett, 10.1055/s-0030-1260324, 17, 2585-2589, 2011.10, The rhenium-catalyzed synthesis of cyclopentenone derivatives via double aldol condensation and successive Nazarov reaction is described. The cyclopentenones were converted to the corresponding cyclopentadienes using organolithium reagents. Cyclopentadienes with four different substituents could be synthesized by stepwise double aldol condensation using a ketone and two types of aldehydes, followed by treatment with an organolithium reagent..
57. Yoichiro Kuninobu, Tomohiro Tatsuzaki, Takashi Matsuki, Kazuhiko Takai, Indium-catalyzed construction of polycyclic aromatic hydrocarbon skeletons via dehydration, Journal of Organic Chemistry, 10.1021/jo200861s, 76, 17, 7005-7009, 2011.09, Polycyclic aromatic compounds can be synthesized from 2-benzylic- or 2-allylbenzaldehydes using a catalytic amount of In(III) or Re(I) complexes. By using this method, polycyclic aza-aromatic compounds can also be prepared efficiently. In these reactions, only water is formed as a side product..
58. Yoichiro Kuninobu, Takuya Yoshida, Kazuhiko Takai, Palladium-catalyzed synthesis of dibenzophosphole oxides via intramolecular dehydrogenative cyclization, Journal of Organic Chemistry, 10.1021/jo201030j, 76, 18, 7370-7376, 2011.09, Dibenzophosphole oxides were obtained from secondary hydrophosphine oxides with a biphenyl group by dehydrogenation via phosphine-hydrogen and carbon-hydrogen bond cleavage in the presence of a catalytic amount of palladium(II) acetate, Pd(OAc) 2. By using this reaction, a ladder-type dibenzophosphole oxide could also be synthesized by double intramolecular dehydrogenative cyclization..
59. Ali Samarat, Yoichiro Kuninobu, Kazuhiko Takai, Synthesis of meso-substituted tetraarylalkynylporphyrins via rhenium-catalyzed formation of naphthalene units, Synlett, 10.1055/s-0030-1261199, 15, 2177-2180, 2011.08, Rhenium-catalyzed synthesis of naphthalene-substituted aryl bromides or iodides via C-H bond activation, and its use for palladium-catalyzed cross-coupling reactions with tetraethynylporphyrin are described. A series of novel meso-substituted tetraalkynylporphyrins with naphthalene moieties were obtained..
60. Yoichiro Kuninobu, Hironori Matsuzaki, Mitsumi Nishi, Kazuhiko Takai, Rhenium-catalyzed regio- and stereoselective addition of two carbon units to terminal alkynes via carbon-carbon bond cleavage of β-keto sulfones, Organic Letters, 10.1021/ol2008507, 13, 11, 2959-2961, 2011.06, Treatment of β-keto sulfones with terminal alkynes gave unsaturated δ-keto sulfones in good to excellent yields under rhenium catalysis. In this reaction, the insertion of the alkynes into the nonstrained carbon-carbon single bond between the α- and β-positions of the β-keto sulfones proceeded smoothly, and (Z)-isomers were produced with high regio- and stereoselectivities..
61. Yoichiro Kuninobu, Kazuhiko Takai, Organic reactions catalyzed by rhenium carbonyl complexes, Chemical Reviews, 10.1021/cr100241u, 111, 3, 1938-1953, 2011.03, Rhenium carbonyl complex-catalyzed synthetic organic reactions are discussed. Kusama and Narasaka reported that a rhenium complex, ReBr(CO) 5, which catalytically promotes Friedel-Crafts acylation. Kusama, Iwasawa, and co-workers reported that the rhenium complex ReCl(CO)5 catalyzes tandem cyclization of ω-ω-acetylenic dienol silyl ethers. Farona and Greenlee reported that a mixture of catalytic amounts of ReX(CO) 5 (X = Cl or Br) and EtAlCl2 promotes olefin metathesis of terminal and internal olefins. The rhenium catalyst is found to promote C-H bond activation followed by insertion of an acrylate, intramolecular nucleophilic cyclization, and finally the elimination of aniline to give the cyclopentadiene derivative, which then complexes to the metal. Fuchikami and co-workers reported the reduction of carboxylic acids to alcohols by dihydrogen..
62. Yoichiro Kuninobu, Takahiro Nakahara, Peng Yu, Kazuhiko Takai, Rhenium-catalyzed insertion of terminal alkenes into a C(sp2)-H bond and successive transfer hydrogenation, Journal of Organometallic Chemistry, 10.1016/j.jorganchem.2010.09.064, 696, 1, 348-351, 2011.01, Treatment of aromatic aldimines with terminal alkenes in the presence of a rhenium catalyst, [HRe(CO)4]n, gives 2-alkenylbenzylamines in good to excellent yields. This reaction proceeds via the insertion of the alkene into a C-H bond at the ortho-position of the imino group of the aromatic aldimine followed by sequential β-hydride elimination from the formed alkyl rhenium intermediate and then by hydrogenation of the imino group of the aldimine..
63. Yoichiro Kuninobu, Mitsumi Nishi, Kazuhiko Takai, Iron-catalyzed synthesis of glycine derivatives via carbon-nitrogen bond cleavage using diazoacetate, Chemical Communications, 10.1039/c0cc03781h, 46, 46, 8860-8862, 2010.12, Treatment of tertiary amines with diazoacetate in the presence of a catalytic amount of an iron salt, FeCl3, in ethanol gave glycine derivatives. In this reaction, a carbon-nitrogen single bond of the amine was cleaved..
64. Yoichiro Kuninobu, Daisuke Asanoma, Kazuhiko Takai, Cross-coupling reactions between C(sp2)-H and C(sp 3)-H bonds via sequential dehydrogenation and C-H insertion, Synlett, 10.1055/s-0030-1259040, 19, 2883-2886, 2010.11, Formal C(sp2)-H and C(sp3)-H cross-coupling reactions were carried out by iridium-catalyzed transfer dehydrogenation of primary alcohols and sequential manganese-catalyzed insertion of the formed aldehydes into a carbon-hydrogen bond of aromatic or olefinic compounds..
65. Yoichiro Kuninobu, Takayuki Seiki, Shunsuke Kanamaru, Yuta Nishina, Kazuhiko Takai, Synthesis of functionalized pentacenes from isobenzofurans derived from C-H bond activation, Organic Letters, 10.1021/ol102349r, 12, 22, 5287-5289, 2010.11, The synthesis of unsymmetric functionalized pentacenes from 1,4-anthraquinones and functionalized isobenzofurans, which were prepared by transformation via C-H bond activation, was successfully accomplished. Examples of the synthesis of pentacenes with functional groups at the 5-position are still rare. These obtained functionalized pentacenes are highly soluble in hexane, toluene, and THF..
66. Yoichiro Kuninobu, Peng Yu, Kazuhiko Takai, Rhenium-catalyzed diastereoselective synthesis of aminoindanes via the insertion of allenes into a C-H bond, Organic Letters, 10.1021/ol101627x, 12, 19, 4274-4276, 2010.10, Figure Presented. Aminoindane derivatives were synthesized diastereoselectively by the treatment of aromatic imines with allenes in the presence of a catalytic amount of a rhenium complex, [HRe(CO)4] n. The allenes inserted into the aromatic C-H bonds..
67. Tomonari Ureshino, Takuya Yoshida, Yoichiro Kuninobu, Kazuhiko Takai, Rhodium-catalyzed synthesis of silafluorene derivatives via cleavage of silicon-hydrogen and carbon-hydrogen bonds, Journal of the American Chemical Society, 10.1021/ja107698p, 132, 41, 14324-14326, 2010.10, The rhodium-catalyzed synthesis of silafluorenes from biphenylhydrosilanes is described. This highly efficient reaction proceeds via both Si-H and C-H bond activation, producing only H2 as a side product. Using this method, a ladder-type bis-silicon-bridged p-terphenyl could also be synthesized..
68. Yoichiro Kuninobu, Tomonari Ureshino, Shun Ichi Yamamoto, Kazuhiko Takai, Regioselective functionalization of alkanes by sequential dehydrogenation-hydrozirconation, Chemical Communications, 10.1039/c0cc00243g, 46, 29, 5310-5312, 2010.07, We have succeeded in formal regioselective functionalization of alkanes by iridium-catalyzed dehydrogenation, hydrozirconation of the resulting alkenes, and electrophilic reaction of the generated alkylzirconium intermediate..
69. Yoichiro Kuninobu, Atsushi Kawata, Salprima S. Yudha, Hisatsugu Takata, Mitsumi Nishi, Kazuhiko Takai, Rhenium- and manganese-catalyzed carbon-carbon bond formation using 1,3-dicarbonyl compounds and alkynes, Pure and Applied Chemistry, 10.1351/PAC-CON-09-09-21, 82, 7, 1491-1501, 2010.07, A rhenium complex, [ReBr(CO)3(thf)]2, catalyzed insertion of terminal alkynes into a C-H bond of active methylene sites of 1,3-dicarbonyl compounds. When a catalytic amount of isocyanide or molecular sieves was added to the reaction mixture, the reaction course changed markedly, and insertion of alkynes into a C-C single bond between α- and β-positions of cyclic and acyclic β-keto esters occurred. The formed acyclic δ-keto esters could be converted to 2-pyranones, which were applied to the synthesis of multisubstituted aromatic compounds via the Diels-Alder reaction and successive elimination of carbon dioxide. In the case of the rhenium-catalyzed reactions between terminal alkynes and β-keto esters without substituent at the α-position, tetrasubstituted benzenes were produced regioselectively by two-to-one reaction of the components. The yields of tetrasubstituted benzenes were improved by using a manganese catalyst..
70. Yoichiro Kuninobu, Takashi Iwanaga, Mitsumi Nishi, Kazuhiko Takai, Rhenium-catalyzed regioselective synthesis of phenol derivatives from 1,3-diesters and terminal alkynes, Chemistry Letters, 10.1246/cl.2010.894, 39, 8, 894-895, 2010.07, Treatment of malonates without a substituent at the active methylene moiety with terminal alkynes gave salicylates regioselectively. In contrast, when malonates bearing a substituent at the active methylene moiety were used, cyclic β-keto esters were generated regioselectively. Treatment of the formed cyclic β-keto esters with In(OTf)
3
gave phenol derivatives via decarboxylation..
71. Yoichiro Kuninobu, Takashi Matsuki, Kazuhiko Takai, Rhenium-catalyzed synthesis of indenones by novel dehydrative trimerization of aryl aldehydes via C-H bond activation, Organic Letters, 10.1021/ol100947p, 12, 13, 2948-2950, 2010.07, By heating aryl aldehydes with catalytic amounts of a rhenium complex, ReBr(CO)5, and N-phenylacetamide in toluene, indenone derivatives are obtained in good to excellent yields. This reaction proceeds via (1) the formation of an isobenzofuran derivative by the insertion of an aldehyde into the C-H bond of another aldehyde (C-H bond activation) and successive intramolecular nucleophilic cyclization, (2) nucleophilic addition of the formed isobenzofuran derivative to the third aldehyde, (3) isomerization, and (4) intramolecular aldol condensation..
72. Yoichiro Kuninobu, Atsushi Kawata, Taihei Noborio, Syun Ichi Yamamoto, Takashi Matsuki, Kazumi Takata, Kazuhiko Takai, Indium-catalyzed synthesis of keto esters from cyclic 1,3-diketones and alcohols and application to the synthesis of seratrodast, Chemistry - An Asian Journal, 10.1002/asia.200900553, 5, 4, 941-945, 2010.04, Esterification reactions from cyclic 1,3-diketones and alcohols are carried out in the presence of several Lewis acids. In particular, indium(III) triflate, In(OTf)3, iron(III) triflate, Fe-(OTf)3, copper(II) triflate, Cu(OTf)2, and silver(I) triflate, AgOTf, show high catalytic activities. These reactions proceed through the carbon-carbon bond cleavage by a retro-aldol reaction and were found to be highly regioselective even in the presence of other functional groups. This type of reaction can also be applied to the preparation of the keto esters during the synthesis of seratrodast, which is an antiasthmatic and eicosanoid antagonist..
73. Yoichiro Kuninobu, Mitsumi Nishi, Atsushi Kawata, Hisatsugu Takata, Yumi Hanatani, S. Salprima Yudha, Aya Iwai, Kazuhiko Takai, Rhenium- and manganese-catalyzed synthesis of aromatic compounds from 1,3-dicarbonyl compounds and alkynes, Journal of Organic Chemistry, 10.1021/jo902072q, 75, 2, 334-341, 2010.01, (Chemical Equation Presented) We have succeeded in the development of three approaches to the synthesis of aromatic compounds from 1,3-dicarbonyl compounds and alkynes. The first approach is a manganese-catalyzed [2+2+2] cycloaddition between 1,3-dicarbonyl compounds, which have no substituents at the active methylene moiety, and terminal alkynes. This reaction proceeds with high regioselectivity when aryl acetylenes are employed as the alkyne component. The second approach is a rhenium- or manganese-catalyzed formal [2+1+2+1] cycloaddition between β-keto esters and two kinds of alkynes. In this reaction, the aromatic compounds are obtained by the following reaction sequence: (1) insertion of the first alkyne into a carbon-carbon single bond of a β-keto ester, (2) formation of 2-pyranones via intramolecular cyclization with the elimination of ethanol, and (3) Diels-Alder reaction between the formed 2-pyranone and the second alkyne. This reaction provides multisubstituted aromatic compounds in a regioselective manner. The third approach is a rheniumcatalyzed formal [2+2+1+1] cycloaddition reaction from two 1,3-diketones and one alkyne. In this reaction, the aromatic skeleton is constructed from three carbons of the first 1,3-diketone, two carbons of the alkyne, and one carbon of the second 1,3-diketone..
74. Yoichiro Kuninobu, Atsuhiro Yamashita, Shun Ichi Yamamoto, Salprima Yudha S., Kazuhiko Takai, Rhenium-catalyzed addition of -enamino esters to allenes, Synlett, 10.1055/s-0029-1218281, 18, 3027-3031, 2009.12, Treatment of β-enamino esters with terminal allenes in the presence of a catalytic amount of a rhenium complex, [ReBr(CO)3(thf)] 2, gave α-alkenylated β-imino or β-enamino esters. In this reaction, a new carbon-carbon bond is formed between the active methylene moiety of the β-enamino esters and the -carbon of the terminal allenes..
75. Yoichiro Kuninobu, Atsushi Kawata, Mitsumi Nishi, Salprima Yudha S, Jingjin Chen, Kazuhiko Takai, Rhenium- and manganese-catalyzed insertion of alkynes into a carbon-carbon single bond of cyclic and acyclic 1,3-dicarbonyl compounds, Chemistry - An Asian Journal, 10.1002/asia.200900137, 4, 9, 1424-1433, 2009.09, Treatment of alkynes with cyclic and acyclic 1,3-dicarbonyl compounds in the presence of a catalytic amount of a rhenium or manganese complex gives ring-expanded and carbon-chain extension products, respectively. In these reactions, alkynes insert into a non-strained carbon-carbon single bond of 1,3-dicarbonyl compounds. The ring-expansion reaction is also promoted by the addition of 4-Å molecular sieves instead of a catalytic amount of an isocyanide..
76. Yoichiro Kuninobu, Takashi Matsuki, Kazuhiko Takai, Rhenium-catalyzed regioselective alkylation of phenols, Journal of the American Chemical Society, 10.1021/ja904360k, 131, 29, 9914-9915, 2009.07, (Chemical Equation Presented) Treatment of phenol derivatives with terminal alkenes in the presence of a catalytic amount of a rhenium complex, Re 2(CO)10, gave monoalkylated phenol derivatives in good to excellent yields. This reaction proceeds at the ortho- or para-position of phenols regioselectively..
77. Yoichiro Kuninobu, Junya Morita, Mitsumi Nishi, Atsushi Kawata, Kazuhiko Takai, Rhenium-catalyzed formation of bicyclo[3.3.1]nonene frameworks by a reaction of cyclic β-keto esters with terminal alkynes, Organic Letters, 10.1021/ol900772h, 11, 12, 2535-2537, 2009.06, Treatment of cyclic βKeto esters with terminal alkynes in the presence of a catalytic amount of a rhenium complex, [ReBr(CO)3(thf)] 2, gave bicyclo[3.3.1]nonene derivatives. The reaction conditions and yields of the bicyclo[3.3.1]nonenes were improved by the sequential use of tetrabutylammonium fluoride (TBAF) after the rhenium-catalyzed reactions..
78. Yoichiro Kuninobu, Yasuo Fujii, Takashi Matsuki, Yuta Nishina, Kazuhiko Takai, Rhenium-catalyzed insertion of nonpolar and polar unsaturated molecules into an olefinic C-H bond, Organic Letters, 10.1021/ol900962v, 11, 12, 2711-2714, 2009.06, Treatment of olefins bearing a directing group with α,β- unsaturated carbonyl compounds, alkynes, or aldehydes in the presence of a catalytic amount of a rhenium complex, [ReBr(CO)3(thf)]2 gave γ,δ-unsaturated carbonyl compounds, dienes, and allyl silyl ethers, respectively. This reaction proceeds via C-H bond activation, insertion of unsaturated molecules into the formed rhenium-carbon bond, and then reductive elimination (or transmetalation in the case of aldehydes)..
79. Yoichiro Kuninobu, Mitsumi Nishi, Salprima S. Yudha, Kazuhiko Takai, Manganese-catalyzed construction of tetrasubstituted benzenes from 1,3-dicarbonyl compounds and terminal acetylenes, Organic Letters, 10.1021/ol800969h, 10, 14, 3009-3011, 2008.12, (Chemical Equation Presented) Treatment of β-keto esters with terminal acetylenes in the presence of a catalytic amount of a manganese complex, MnBr(CO) 5, and molecular sieves, gave multisubstituted aromatic compounds in good to excellent yields. This reaction employs [2 + 2 + 2] cycloaddition of β-keto esters and 2 equiv of terminal acetylenes with dehydration. In the case of a 1,3-diketone, the corresponding acetophenone derivative and its deacylated compound can be synthesized selectively..
80. Yoichiro Kuninobu, Yuta Nishina, Kayo Okaguchi, Makoto Shouho, Kazuhiko Takai, Reactions and mechanistic studies of rhenium-catalyzed insertion of α,β-unsaturated carbonyl compounds into a C-H bond, Bulletin of the Chemical Society of Japan, 10.1246/bcsj.81.1393, 81, 11, 1393-1401, 2008.12, A rhenium complex, [ReBr(CO)3(thf)]2, catalyzes the insertion of α, β-unsaturated carbonyl compounds into a C-H bond of aromatic compounds having nitrogen-containing directing groups. In this reaction, Re2(CO)10 can also be used as a catalyst. When imines are employed as the aromatic substrates, sequential cyclization proceeds and indene derivatives are obtained in good to excellent yields. This reactivity is in contrast to those of ruthenium and rhodium complexes, which are usually used as catalysts in the insertion reactions of unsaturated molecules into a C-H bond. Investigations on the reaction mechanism indicate that the rhenium catalyst promotes C-H bond activation of aromatic compounds, the insertion of α, β-unsaturated carbonyl compounds into a Re-C bond, and intramolecular nucleophilic cyclization followed by reductive elimination and the elimination of an amine..
81. Yoichiro Kuninobu, Atsushi Kawata, Mitsumi Nishi, Hisatsugu Takata, Kazuhiko Takai, Rhenium- and manganese-catalyzed insertion of acetylenes into β-keto esters
Synthesis of 2-pyranones, Chemical Communications, 10.1039/b814694b, 47, 6360-6362, 2008.12, Rhenium- and manganese-catalyzed reactions between β-keto esters and acetylenes, followed by treatment with tetrabutylammonium fluoride, gave 2-pyranone derivatives regioselectively..
82. Yoichiro Kuninobu, Hisatsugu Takata, Atsushi Kawata, Kazuhiko Takai, Rhenium-catalyzed synthesis of multisubstituted aromatic compounds via C-C single-bond cleavage, Organic Letters, 10.1021/ol801226t, 10, 14, 3133-3135, 2008.12, (Chemical Equation Presented) A reaction between a β-keto ester and an acetylene in the presence of a rhenium complex, [ReBr(CO)3(thf)] 2, as a catalyst, provided a 2-pyranone derivative in excellent yield via retro-aldol reaction (C-C single bond cleavage). By adding an acetylene-bearing ester group(s) after the formation of 2-pyranones, an aromatization reaction proceeded and multisubstituted aromatic compounds were obtained in good to excellent yields..
83. Salprima Yudha S, Yoichiro Kuninobu, Kazuhiko Takai, Rhenium-catalyzed synthesis of stereodefined cyclopentenes from β-ketoesters and aliphatic allenes, Angewandte Chemie - International Edition, 10.1002/anie.200803350, 47, 48, 9318-9321, 2008.11, (Chemical Equation Presented) Come on allene: Commercially available [Re2(CO)10] as a catalyst provides five-membered carbocycles in moderate to excellent yields with high stereoselectivity (see scheme). The configuration at each of the three sp3 carbon centers of the ring is defined. The reaction proceeds at the β, γ, and adjacent methylene positions of the allene; previously, similar reactions usually occurred at the α, β, and γ positions of the allene..
84. Yoichiro Kuninobu, Yuta Nishina, Takashi Matsuki, Kazuhiko Takai, Synthesis of Cp-Re complexes via olefinic C-H activation and successive formation of cyclopentadienes, Journal of the American Chemical Society, 10.1021/ja805921f, 130, 43, 14062-14063, 2008.10, Treatment of an α,β-unsaturated ketimine with an α,β-unsaturated carbonyl compound in the presence of a rhenium complex, Re2(CO)10, gave a cyclopentadienyl-rhenium complex. This reaction proceeds via rhenium-catalyzed C-H bond activation of an olefinic C-H bond, insertion of an α,β-unsaturated carbonyl compound into a Re-C bond of the alkenylrhenium intermediate, intramolecular nucleophilic cyclization, reductive elimination, elimination of aniline to give a cyclopentadiene derivative, followed by the formation of a cyclopentadienyl-rhenium complex from the cyclopentadiene derivative and the rhenium complex..
85. Yoichiro Kuninobu, Hirokazu Ueda, Kazuhiko Takai, Rhenium-catalyzed coupling of 2-propynyl alcohols and several nucleophiles via dehydration, Chemistry Letters, 10.1246/cl.2008.878, 37, 8, 878-879, 2008.08, Treatment of 2-propynyl alcohols with several nucleophiles in the presence of a catalytic amount of a rhenium complex, [ReBr(CO)3(thf)] 2, gave coupling products via dehydration. In these reactions, C-C, C-O, and C-S bonds can be constructed under mild conditions..
86. Yoichiro Kuninobu, Kou Kikuchi, Kazuhiko Takai, Manganese-catalyzed synthesis of hydantoin derivatives from terminal alkynes and isocyanates, Chemistry Letters, 10.1246/cl.2008.740, 37, 7, 740-741, 2008.07, Hydantoin derivatives were obtained by the reactions of terminal alkynes with isocyanates in the presence of a catalytic amount of a manganese complex, MnBr(CO)5. This reaction also proceeded using a rhenium complex, Re2(CO)10, or an iron complex, Fe(CO)5, as a catalyst..
87. Yutaka Matsuo, Yoichiro Kuninobu, Ayako Muramatsu, Masaya Sawamura, Eiichi Nakamura, Synthesis of metal fullerene complexes by the use of fullerene halides, Organometallics, 10.1021/om8001262, 27, 14, 3403-3409, 2008.07, K(C60R5) (1, R = Me, Ph) was generated by deprotonation of C60R5H (2) and allowed to react with N-fluoropyridinium triflate and N-chloro- and N-bromosuccinimide in benzene at 25°C for 10 min to obtain halogenated fullerenes C60R 5X (3a: R = Me, X = F; 3b: R = Me, X = Cl; 3c: R = Me, X = Br; 4a: R = Ph, X = F; 4b: R = Ph, X = Cl, 4c: R = Ph, X = Br) in good yield. The pentamethyl[60]fullerene halides are useful for the synthesis of a variety of η5-fullerene metal complexes. The reaction of the fullerene bromide 3c with the low-valent transition metal complexes Na[Re(CO) 4], Fe(CO)5, Ru3(CO)12, and Na[Co(CO)4] gave Re(η5-C60Me 5)(CO)3 (5), Fe(η5-C60Me 5)Br(CO)2 (6), Ru(η5-C60Me 5)Br(CO)2 (7), and Co(η5-C 60Me5)(CO)2 (8), respectively. The structures of halide 3c and rhenium complex 5 were determined by X-ray crystallography. Electrochemical measurements on 3b and 3c were also performed. The iron complex 6 was converted into Fe(η5-C60Me5)Cp (9), Fe(η5-C60Me5)Me(CO)2 (10), Fe(η5-C60Me5)(CO)2(CCH) (11), and Fe(η5-C60Me5)(CO)2(CCPh) (12), by ligand exchange reactions..
88. Yoichiro Kuninobu, Kou Kikuchi, Yukimi Tokunaga, Yuta Nishina, Kazuhiko Takai, Hydroarylation of acetylenes, acrylates, and isocyanates with heteroaromatic compounds under rhenium catalysis, Tetrahedron, 10.1016/j.tet.2008.01.145, 64, 26, 5974-5981, 2008.06, With the aid of a directing group, an imine moiety, heteroaromatic compounds add to acetylenes in the presence of a catalytic amount of [ReBr(CO)3(THF)]2 at the adjacent position of the directing group regioselectively to give hydroarylation of the acetylenes in good to excellent yields. Similarly, heteroaromatic compounds react with acrylates and isocyanates to give the corresponding hydroarylation products under rhenium catalysis..
89. Yoichiro Kuninobu, Yuta Nishina, Atsushi Kawata, Makoto Shouho, Kazuhiko Takai, Rhenium-catalyzed synthesis of indene derivatives via C-H bond activation, Pure and Applied Chemistry, 10.1351/pac200880051149, 80, 5, 1149-1154, 2008.05, Rhenium complex, [ReBr(CO)3(thf)]2-catalyzed reactions between aromatic imines and either acetylenes or α,β- unsaturated carbonyl compounds gave indene derivatives in good to excellent yields. These reactions proceed via C-H bond activation, insertion of acetylenes or α,β-unsaturated carbonyl compounds, intramolecular nucleophilic cyclization, and reductive elimination. Indene derivatives were also obtained from aromatic ketones and α,β-unsaturated carbonyl compounds in the presence of catalytic amounts of the rhenium complex and p-anisidine. Sequential ruthenium-catalyzed hydroamination of aromatic acetylenes with anilines, and rhenium-catalyzed reactions of the formed aromatic ketimines with α,β-unsaturated carbonyl compounds also provided indene derivatives..
90. Yoichiro Kuninobu, Yuichi Inoue, Kazuhiko Takai, Copper(I)- And gold(I)-catalyzed synthesis of 2,4-disubstituted quinoline derivatives from N-Aryl-2-propynylamines, Chemistry Letters, 10.1246/cl.2007.1422, 36, 12, 1422-1423, 2007.12, 2,4-Disubstituted quinoline derivatives were obtained from N-aryl-2-propynylamines catalyzed by copper(I) and gold(I) complexes. The quinoline derivatives could also be obtained by the reaction of N-arylaldimines with terminal acetylenes via the formation of N-aryl-2-propynylamines..
91. S. Salprima Yudha, Yoichiro Kuninobu, Kazuhiko Takai, Rhenium-catalyzed hydroamidation of unactivated terminal alkynes
Synthesis of (E)-enamides, Organic Letters, 10.1021/ol702564e, 9, 26, 5609-5611, 2007.12, Reactions of cyclic amides with unactivated terminal alkynes in the presence of a catalytic amount of a rhenium complex provided (E)-enamides in high regio- and stereoselectivity (E:Z = >99:<1)..
92. Atsushi Kawata, Kazumi Takata, Yoichiro Kuninobu, Kazuhiko Takai, Indium-catalyzed retro-claisen condensation, Angewandte Chemie - International Edition, 10.1002/anie.200702798, 46, 41, 7793-7795, 2007.10, (Chemical Equation Presented) Retro-aldol reaction: Indium-catalyzed reaction of a 1,3-diketone with an alcohol proceeds under solvent-free conditions by nucleophilic attack of the alcohol on a carbonyl group of the 1,3-diketone and carbon-carbon bond cleavage by a retro-Claisen condensation to give an ester in high yield (see scheme). Using water and an amine as nucleophiles instead of an alcohol gave the corresponding carboxylic acid and amide..
93. Yoichiro Kuninobu, Yuta Nishina, Takahiro Takeuchi, Kazuhiko Takai, Manganese-catalyzed insertion of aldehydes into a C-H bond, Angewandte Chemie - International Edition, 10.1002/anie.200702256, 46, 34, 6518-6520, 2007.09, (Chemical Equation Presented) Mn gets in the game: In the presence of a manganese catalyst and a stoichiometric amount of hydrosilane, aldehydes insert into C-H bonds of aromatic rings of compounds with directing groups (see scheme). This first example of a manganese-catalyzed chemical transformation through C-H bond activation gives silyl ethers in good to excellent yields and can also be applied to asymmetric transformation..
94. Yoichiro Kuninobu, Peng Yu, Kazuhiko Takai, Rhenium-catalyzed [2 + 2] cycloadditions of norbornenes with internal and terminal acetylenes, Chemistry Letters, 10.1246/cl.2007.1162, 36, 9, 1162-1163, 2007.09, Treatment of norbornenes with internal and terminal acetylenes in the presence of a catalytic amount of [ReBr(CO)3(thf)]2 gave cyclobutene derivatives in good to excellent yields..
95. Yoichiro Kuninobu, Hirokazu Ueda, Atsushi Kawata, Kazuhiko Takai, Rearrangement of indene skeletons under mild conditions, Journal of Organic Chemistry, 10.1021/jo070537w, 72, 18, 6749-6752, 2007.08, (Chemical Equation Presented) Isomerization between two isomers of 1,2-disubstituted 3-aminoindenes occurs via the rearrangement of indene frameworks. In contrast to previous rearrangements of indene derivatives, which occur under high-temperature conditions or the irradiation of light, this rearrangement proceeds at room temperature without UV light irradiation. An amino group at the 3-position plays an important role to accelerate the rearrangement under mild conditions..
96. Yoichiro Kuninobu, Yuta Nishina, Kazuhiko Takai, Rhenium-catalyzed synthesis of naphthalene derivatives via insertion of aldehydes into a C-H bond, Tetrahedron, 10.1016/j.tet.2007.05.083, 63, 35, 8463-8468, 2007.08, A rhenium complex, [ReBr(CO)3(THF)]2, catalyzed reactions of aromatic ketimines and aldehydes with dienophiles, followed by dehydration, to give naphthalene derivatives in good to excellent yields. This reaction proceeds via C-H bond activation, insertion of an aldehyde, intramolecular nucleophilic cyclization, reductive elimination, elimination of aniline and Diels-Alder reaction. After dehydration, naphthalene derivatives were formed..
97. Yoichiro Kuninobu, Yukimi Tokunaga, Kazuhiko Takai, Rhenium-catalyzed amidation of heteroaromatic compounds via C-H bond activation, Chemistry Letters, 10.1246/cl.2007.872, 36, 7, 872-873, 2007.07, Regioselective insertion of isocyanates into a C-H bond of heteroaromatic compounds took place using a rhenium catalyst, [ReBr(CO) 3(thf)] 2..
98. Yoichiro Kuninobu, Eri Ishii, Kazuhiko Takai, Rhenium- and gold-catalyzed coupling of aromatic aldehydes with trimethyl(phenylethynyl)silane
Synthesis of diethynylmethanes, Angewandte Chemie - International Edition, 10.1002/anie.200700183, 46, 18, 3296-3299, 2007.06, (Chemical Equation Presented) Very couply! Coupling reactions of propargyl or benzyl alcohols with allyl- or alkynylsilanes proceed efficiently using [{ReBr(CO)3(thf)}2] as catalyst. Additionally, diethynylmethane derivatives were obtained by the reaction of aromatic aldehydes with trimethyl(phenylethynyl)silane in the presence of both the rhenium complex and AuCl (see scheme)..
99. Yoichiro Kuninobu, Yuichi Inoue, Kazuhiko Takai, Rhenium-catalyzed addition of trimethylsilylacetylene to aldimines, Chemistry Letters, 10.1246/cl.2006.1376, 35, 12, 1376-1377, 2006.12, A rhenium complex, [ReBr(CO)3(thf)]2, catalyzes reactions of aldimines with trimethylsilylacetylene to give propargylamines in excellent yields. The reactions proceed at room temperature under solvent-free conditions..
100. Yoichiro Kuninobu, Atsushi Kawata, Kazuhiko Takai, Efficient catalytic insertion of acetylenes into a carbon-carbon single bond of nonstrained cyclic compounds under mild conditions, Journal of the American Chemical Society, 10.1021/ja064022i, 128, 35, 11368-11369, 2006.09, A rhenium complex, [ReBr(CO)3(thf)]2, catalyzes the reaction of a 1,3-dicarbonyl cyclic compound with an acetylene to give a medium-sized cyclic compound in excellent yield. By using isocyanide as an additive, the catalytic activity of the rhenium complex changes dramatically, and the insertion of acetylenes into a carbon-carbon single bond occurs under mild conditions. A plausible mechanism is that the reaction proceeds via the formation of a rhenacyclopentene intermediate, ring opening by a retro-aldol reaction, isomerization, and reductive elimination..
101. Yoichiro Kuninobu, Yuta Nishina, Chie Nakagawa, Kazuhiko Takai, Rhenium-catalyzed insertion of aldehyde into a C-H bond
Synthesis of isobenzofuran derivatives, Journal of the American Chemical Society, 10.1021/ja065643e, 128, 38, 12376-12377, 2006.09, A rhenium complex, [ReBr(CO)3(thf)]2, catalyzed reactions of aromatic ketimines with aldehydes to give isobenzofuran derivatives in good to excellent yields. In contrast to ruthenium and rhodium catalysts, aldehydes, which are polar unsaturated molecules, inserted into the C-H bond after activation by the rhenium complex..
102. Yoichiro Kuninobu, Yuta Nishina, Kazuhiko Takai, Sequential ruthenium-catalyzed hydroamination and rhenium-catalyzed C-H bond activation leading to indene derivatives, Organic Letters, 10.1021/ol0611292, 8, 13, 2891-2893, 2006.06, Formal [3+2] annulation of arylacetylenes and α,β-unsaturated carbonyl compounds is achieved in a one-pot reaction by successive treatment of the acetylenes with aniline and a catalytic amount of Ru3(CO) 12 and NH4PF6 and C-H bond activation catalyzed by [ReBr(CO)3(thf)]2. The result suggests that the second rhenium-catalyzed indene formation is not disturbed by the first catalyst system..
103. Yoichiro Kuninobu, Shuhei Nishimura, Kazuhiko Takai, Isocyanate acting as a carbonyl precursor
Pyridyl group-assisted formation of 4H-pyrido[1,2-a]pyrimidin-4-ones from ketimines and isocyanates, Organic and Biomolecular Chemistry, 10.1039/b516916j, 4, 2, 203-205, 2006.04, By the reactions of ketimines bearing a pyridyl or a picolyl group on a nitrogen atom of the imine moiety with tosylisocyanate, 4H-pyrido[1,2-a] pyrimidin-4-one derivatives could be obtained in quantitative yields. In these reactions, tosylisocyanate acts as a carbonyl precursor. The pyridyl or picolyl group is a key functional group because it is not only the constituent structure of the 4H-pyrido[1,2-a]pyrimidin-4-one framework but also the promoter of the formation of a ketene intermediate..
104. Yoichiro Kuninobu, Yuta Nishina, Makoto Shouho, Kazuhiko Takai, Rhenium- and aniline-catalyzed one-pot annulation of aromatic ketones and α,β-unsaturated esters initiated by C-H bond activation, Angewandte Chemie - International Edition, 10.1002/anie.200503627, 45, 17, 2766-2768, 2006.04, (Chemical Equation Presented) Several reaction steps, including C-H activation, lead to indene derivatives in good yields in the rhenium-catalyzed reaction of aromatic ketimines and ethyl acrylate. Indene derivatives can also be obtained by the reactions of aromatic ketones with α,β-unsaturated esters in the presence of a catalytic rhenium complex and p-anisidine (see scheme)..
105. Yoichiro Kuninobu, Yukimi Tokunaga, Atsushi Kawata, Kazuhiko Takai, Insertion of polar and nonpolar unsaturated molecules into carbon-rhenium bonds generated by C-H bond activation
Synthesis of phthalimidine and indene derivatives, Journal of the American Chemical Society, 10.1021/ja054216i, 128, 1, 202-209, 2006.01, A rhenium complex, [ReBr(CO)3(thf)]2, catalyzes the reaction of an aromatic aldimine with an isocyanate and an acetylene to give a phthalimidine and an indene derivative in a quantitative yield, respectively. The reactions proceed via C-H bond activation, insertion of the isocyanate or the acetylene, Intramolecular nucleophilic cyclization to the aldimine of the generated amido- or alkenyl-rhenium species, and reductive elimination. In contrast to ruthenium and rhodium catalysts, which are usually employed in this type of reaction, the rhenium catalyst promotes the insertion of a polar unsaturated molecule. This occurs more easily than the insertion of a nonpolar unsaturated molecule..
106. Yoichiro Kuninobu, Atsushi Kawata, Kazuhiko Takai, Rhenium-catalyzed formation of indene frameworks via C-H bond activation
[3+2] Annulation of aromatic aldimines and acetylenes, Journal of the American Chemical Society, 10.1021/ja0528174, 127, 39, 13498-13499, 2005.10, A rhenium complex, [ReBr(CO)3(thf)]2, catalyzes the reaction of an aromatic aldimine with an acetylene to give an indene derivative in a quantitative yield. The reaction proceeds via C-H bond activation, insertion of the acetylene, intramolecular nucleophilic cyclization, and reductive elimination. In contrast to ruthenium and rhodium catalysts, which are usually employed in this type of reaction, the rhenium catalyst promotes the intramolecular nucleophilic cyclization of the alkenylmetal species generated by insertion of the acetylene..
107. Yoichiro Kuninobu, Atsushi Kawata, Kazuhiko Takai, Rhenium-catalyzed insertion of terminal acetylenes into a C-H bond of active methylene compounds, Organic Letters, 10.1021/ol0515208, 7, 22, 4823-4825, 2005.10, (Chemical Equation Presented) A rhenium complex, [ReBr(CO) 3(thf)]2, catalyzed the intermolecular reactions of 1,3-dicarbonyl compounds with terminal acetylenes and gave the corresponding alkenyl derivatives in excellent yields. These reactions could apply to an intramolecular version and gave the corresponding cyclic compounds quantitatively..
108. Rolfe H. Herber, Israel Nowik, Yutaka Matsuo, Motoki Toganoh, Yoichiro Kuninobu, Eiichi Nakamura, Mössbauer spectroscopy of bucky ferrocenes
Lattice dynamics and motional anisotropy of the metal atom, Inorganic Chemistry, 10.1021/ic050251e, 44, 16, 5629-5635, 2005.08, Temperature-dependent 57Fe Mössbauer effect spectroscopy has been used to elucidate the metal atom dynamics in three neutral and two cationic bucky ferrocenes. For the three diamagnetic complexes Fe(C 60H5)Cp (1), Fe(C60Me5)Cp (2), and Fe(C60Ph5)Cp (3), the metal atom motion is anisotropic and the temperature dependence of the mean-square amplitude of vibration of the metal atom at a number of temperatures is reported. The Mössbauer lattice temperatures have been determined and compared to the parent ferrocene (6). The synthesis and X-ray crystal structure of 3 have been determined at 153(2) K, and the 1H and 13C NMR spectra have been recorded. The cationic complexes derived from 2 and 3 show spin-lattice relaxation. The relaxation rate appears insensitive to the nearest-neighbor environment of the metal atom in this pair..
109. Toshihiko Kaji, Toshihiro Shimada, Hiroaki Inoue, Yoichiro Kuninobu, Yutaka Matsuo, Eiichi Nakamura, Koichiro Saiki, Molecular orientation and electronic structure of epitaxial bucky ferrocene (Fe(C60(CH3)5)C5H 5) thin films, Journal of Physical Chemistry B, 108, 28, 9914-9918, 2004.07, Single crystalline epitaxial films of bucky ferrocene (Fe(C 60(CH3)5)C5H5), a hybrid molecule of C60 and ferrocene, were grown on MoS2(0001) substrates. By using reflection high-energy electron diffraction (RHEED) amplified by a microchannel plate (MCP), it was found that the lattice constant of the film decreased from 11.3 ± 0.2 Å at 1-2 monolayer (ML) to 10.2 ± 0.2 Å at 3 ML or thicker. Both of the lattice constants were incommensurate with that of the substrate, which indicates a new type of epitaxial growth. Valence electronic structures of the films at each thickness were measured with ultraviolet photoelectron spectroscopy (UPS) and the energy levels of molecular orbitals were identified in relation to the molecular orientation in the epitaxial film..
110. Yoichiro Kuninobu, Yutaka Matsuo, Motoki Toganoh, Masaya Sawamura, Eiichi Nakamura, Nickel, palladium, and platinum complexes of η 5- cyclopentadienide C 60R 5 ligands. Kinetic and thermodynamic stabilization effects of the C 60Ph 5 ligand, Organometallics, 10.1021/om0499153, 23, 13, 3259-3266, 2004.06, The nickel-, palladium-, and platinum-RFC p complexes η 5-RFC p)(η 3-allylic) (3b, RFC p = C 60R 5, R = Me, allylic = methallyl; 4a, R = Ph, allylic = allyl; 4b, R = Ph, allylic = methallyl), Pd(η 5- RFC p)(η 3-allylic) (7a, R = Me, allylic = allyl; 7b, R = Me, allylic = methallyl; 7c, R = Me, allylic = crotyl; 8a, R = Ph, allylic = allyl; 8b, R = Ph, allylic = methallyl; 8c, R = Ph, allylic = crotyl), and Pt(η 5-RFC p)(η 3-methallyl) (9, R = Me; 10, R = Ph), were synthesized by transmetalation between K(RFC p) (R = Me, Ph) and [Ni(allylic)Br] 2, [Pd(allylic)Cl] 2, or [Pt(methallyl)Cl] 2 in THF at 25 °C for 10 min. The nickel-PhFC p complexes 4a,b are unusually more stable toward molecular oxygen than the corresponding simple nickel cyclopentadienides and survive in air for many hours at elevated temperature. The crystal structures and the electrochemical properties of the palladium complexes suggest that the unusual stability of the PhFC p complexes is due to the kinetic stabilization effect of the five Ph groups surrounding the metal atom and the thermodynamic stabilization effect of the electron-withdrawing fullerene moiety, hence suggesting new opportunities for the synthesis of otherwise unstable organometallic compounds..
111. Toshihiro Shimada, Yoshiro Yamamoto, Toshihiko Kaji, Kenji Itaka, Hideomi Koinuma, Yoichiro Kuninobu, Yutaka Matsuo, Eiichi Nakamura, Koichiro Saiki, Photoinduced change in the Raman spectrum of buckyferrocene ((Fe(C 60(CH3)5)C5H5), Solid State Communications, 10.1016/j.ssc.2004.07.046, 132, 3-4, 197-201, 2004.01, The Raman spectrum of buckyferrocene (Fe(C60(CH 3)5)C5H5) changes during laser irradiation at 532 nm. A peak at 1465 cm-1 decreases and a new peak at 1452 cm-1 emerges, which resembles the change in the 'pentagonal pinch mode' during the photopolymerization of C60. Photoinduced polymerization is strongly suggested because fragments from the buckyferrocene dimers are observed during the mass spectroscopy of laser desorbed solid samples. The rate constants of the photoinduced change for the powder crystals were determined at various photon intensities, and linearity was observed. The photoinduced change seems to occur extremely fast in densely packed buckyferrocene films fabricated by vacuum deposition..
112. Yutaka Matsuo, Yoichiro Kuninobu, Shingo Ito, Eiichi Nakamura, Synthesis and reactivity of bucky ruthenocene Ru(η5-C 60Me5)(η5-C5H5), Chemistry Letters, 10.1246/cl.2004.68, 33, 1, 68-69, 2004.01, Metathetical coupling of an η5-fullerene ruthenium complex Ru(η5-C60Me5)Cl(CO)2 and sodium cyclopentadienide gives a molecular hybrid of ruthenocene and fullerene, Ru(η5-C60Me5)(η5-C 5H5) (bucky ruthenocene), the structure of which was determined by spectroscopic and crystallographic analyses. The molecule shows unique reactivity among known ferrocene and ruthenocene compounds..
113. Masaya Sawamura, Yoichiro Kuninobu, Motoki Toganoh, Yutaka Matsuo, Masahiro Yamanaka, Eiichi Nakamura, Hybrid of ferrocene and fullerene, Journal of the American Chemical Society, 10.1021/ja026069j, 124, 32, 9354-9355, 2002.08, "Bucky ferrocenes", molecular hybrids of ferrocene and fullerene, have been synthesized in good yield on gram scale by treatment of C60HMe5 or C70HMe3 with [FeCp(CO)2]2 and their structures studied with physical methods including X-ray crystallography..
114. T. Shimada, H. Nakatani, K. Ueno, A. Koma, Yoichiro Kuninobu, M. Sawamura, E. Nakamura, Epitaxial growth and electronic structure of a C60 derivative prepared by using a solution spray technique, Journal of Applied Physics, 10.1063/1.1379052, 90, 1, 209-212, 2001.07, We demonstrate and analyze the epitaxial film formation of a molecular material that cannot be evaporated in vacuum due to thermal decomposition. A solution of the material is sprayed onto single crystalline van der Waals surfaces using a pulse valve under controlled vapor pressure of the solvent. Monolayer epitaxial films are obtained and we propose that the growth is mediated by liquid ultrathin films formed on the surface. Molecular arrangement and electronic structure of C60(CH3)5H films are studied by reflection high energy electron diffraction and ultraviolet photoelectron spectroscopy, respectively. The present technique will be useful to study the electronic structure of recently synthesized molecular materials..
115. M. Sawamura, Yoichiro Kuninobu, E. Nakamura, Half-sandwich metallocene embedded in a spherically extended π-conjugate system. Synthesis, structure, and electrochemistry of Rh(η5-C60Me5)(CO)2, Journal of the American Chemical Society, 10.1021/ja005564h, 122, 49, 12407-12408, 2000.12.
116. Masaya Sawamura, Motoki Toganoh, Yoichiro Kuninobu, Seiichi Kato, Eiichi Nakamura, Synthesis of pentamethyl-monohydro[60]fullerene C60Me5H and its use as cyclopentadienyl-type ligand precursor, Chemistry Letters, 10.1246/cl.2000.270, 3, 270-271, 2000.01, Pentamethyl-monohydro[60]fullerene C60Me5H has been synthesized through five-fold addition of methyleopper reagent to C60. The anion C60Me5 generated by deprotonation of C60Me5H forms organometallic complexes with K+ and Tl+ ions with stronger metal-carbon interaction than that in the corresponding pentaphenylated ligand C60Ph5 +..