Kyushu University Academic Staff Educational and Research Activities Database
List of Reports
Makoto Tokunaga Last modified date:2022.03.29

Professor / Multidisciplinary chemistry / Department of Chemistry / Faculty of Sciences

1. M. Kitamura, T. Ohkuma, Makoto Tokunaga, R. Noyori, Dynamic kinetic resolution in BINAP-ruthenium(II) catalyzed hydrogenation of 2-substituted 3-oxo carboxylic esters, Tetrahedron Asymmetry, 10.1016/S0957-4166(00)82262-4, 1990.01, BINAP-Ru catalyzed hydrogenation allows efficient dynamic kinetic resolution of certain 2-substituted 3-oxo carboxylic esters having cyclic structures to lead to the alcoholic products in high enantiomeric and diastereomeric excesses..
2. M. Kitamura, Makoto Tokunaga, T. Ohkuma, R. Noyori, Convenient preparation of binap-ruthenium(II) complexes catalyzing asymmetric hydrogenation of functionalized ketones, Tetrahedron Letters, 10.1016/S0040-4039(00)79892-3, 1991.08, Ligand exchange between [RuCl2(benzene)]2 or RuCl2[Sb(C6H5)3]3 and (R)- or (S)-BINAP produces BINAP-Ru(II) complexes which act as catalysts for the highly enantioselective hydrogenation of functionalized ketones..
3. Masato Kitamura, Makoto Tokunaga, Ryoji Noyori, Practical synthesis of BINAP-ruthenium(II) dicarboxylate complexes, Journal of Organic Chemistry, 1992.
4. M. Kitamura, Makoto Tokunaga, R. Noyori, Quantitative Expression of Dynamic Kinetic Resolution of Chirally Labile Enantiomers
Stereoselective Hydrogenation of 2-Substituted 3-Oxo Carboxylic Esters Catalyzed by BINAP-Ruthenium(II) Complexes
, Journal of the American Chemical Society, 10.1021/ja00054a020, 1993.01, Hydrogenation of chirally unstable 2-substituted 3-oxo carboxylic esters gives a mixture of four stereoisomeric hydroxy esters. Use of BINAP-Ru(II) complex catalysts allows selective production of one stereoisomer among four possible isomers. The stereoselectivity obtained by the dynamic kinetic resolution depends on facile in situ racemization of the substrates, efficient chirality recognition ability of the catalysts, and the structures of the ketonic substrate. The factors controlling the efficiency of the stereoselective hydrogenation are experimentally determined by reaction of racemic oxo esters using enantiomerically pure and racemic BINAP complexes. Quantitative expression of the dynamic kinetic resolution has been made by defining the product partition coefficients (w, x, y, and z), the relative reactivities of the enantiomeric substrates (kfast/kSl0W), and the relative ease with which stereoinversion and hydrogenation take place (kinv/kfast). The validity of the equations has been demonstrated by the graphical exhibition of the enantioselectivity and diastereoselectivity as a function of conversion of the substrates..
5. M. Kitamura, Makoto Tokunaga, R. Noyori, Mathematical treatment of kinetic resolution of chirally labile substrates, Tetrahedron, 10.1016/S0040-4020(01)80541-X, 1993.02, Kinetic resolution of chirally unstable compounds prone to racemize has been quantitatively analyzed. Enantiomeric purities of the products as a function of conversion can be graphically displayed. This approach may be useful for designing an efficient asymmetric reaction..
6. J. W. Falle, Makoto Tokunaga, Chiral poisoning in the kinetic resolution of allylic alcohols, Tetrahedron Letters, 10.1016/S0040-4039(00)60125-9, 1993.11, Recently, hydrogenations of allylic alcohols using ruthenium catalysts with enantiomerically pure phosphines, such as (R)-BINAP were reported to be useful for the kinetic resolution of cyclic allylic alcohols. These kinetic resolutions can also be effected using racemic BINAP and preferentially deactivating one enantiomer of the catalyst with an enantiomerically pure chiral poison. Poisoning of racemic (BINAP)-RuCl2 (dmf)x with (1R,2S)-ephedrine provided (R)-2-cyclohexenol in 93% ee at 72% conversion..
7. Takao Ikariya, Philip G. Jessop, Makoto Tokunaga, Ryoji Noyori, Homogeneous Hydrogenation of Carbon Dioxide with Transition Metal Complexes, Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry, 10.5059/yukigoseikyokaishi.52.1032, 1994, Recent advances in the efficiency of the homogeneous catalytic reduction of carbon dioxide may bring CO2 fixation by this method from a research curiosity into an industrially applicable process. The reduction of CO2 to bulk chemicals such as dimethylformamide, methyl formate, and methanol offers a safer alternative to toxic CO-based processes. This review describes stoichiometric and homogeneously catalyzed reactions of CO2, especially those which involve hydrogenation by hydrogen gas. The newly discovered advantages of supercritical CO2 as a medium for its own fixation will be particularly highlighted..
8. J. W. Faller, Maria R. Mazzieri, Jenna Thu Nguyen, Jonathan Parr, Makoto Tokunaga, Controlling stereochemistry in C-C and C-H bond formation with electronically asymmetric organometallics and chiral poisons, Pure and Applied Chemistry, 10.1351/pac199466071463, 1994.01, Air stable (cyclopentadienyl)Mo(NO)(halide)(η3-allyl) complexes add to aldehydes to yield homoallylic alcohols in high enantioselectivity and diastereoselectivity. A new strategy, chiral poisoning, is applied to asymmetric hydrogenation and the kinetic resolution of allylic alcohols using transition metal catalysts prepared from racemic bis-phosphine ligands..
9. M. Kitamura, Makoto Tokunaga, R. Noyori, Asymmetric hydrogenation of β-keto phosphonates
A practical way to fosfomycin
, Journal of the American Chemical Society, 10.1021/ja00115a030, 1995.03.
10. Masato Kitamura, Makoto Tokunaga, Trang Pham, William D. Lubell, Ryoji Noyori, Asymmetric synthesis of α-amino β-hydroxy phosphonic acids via BINAP-ruthenium catalyzed hydrogenation, Tetrahedron Letters, 10.1016/0040-4039(95)01135-5, 1995.08, BINAP-Ru catalyzed hydrogenation of configurationally labile α-amido β-keto phosphonic esters gives the (R,R)- or (S,S)-α-amido β-hydroxy phosphonic esters in a highly enantio- and diastereoselective manner..
11. Eric N. Jacobsen, Fumitoshi Kakiuchi, Reed G. Konsler, Jay F. Larrow, Makoto Tokunaga, Enantioselective catalytic ring opening of epoxides with carboxylic acids, Tetrahedron Letters, 10.1016/S0040-4039(96)02414-8, 1997.02, The chiral Co(salen) complex 3 is an effective catalyst for the asymmetric ring-opening of meso epoxides with benzoic acid. Enantioselectivities of 55-93% were obtained with a range of substrates..
12. Makoto Tokunaga, Jay F. Larrow, Fumitoshi Kakiuchi, Eric N. Jacobsen, Asymmetric catalysis with water
Efficient kinetic resolution of terminal epoxides by means of catalytic hydrolysis
, Science, 10.1126/science.277.5328.936, 1997.08, Epoxides are versatile building blocks for organic synthesis. However, terminal epoxides are arguably the most important subclass of these compounds, and no general and practical method exists for their production in enantiomerically pure form. Terminal epoxides are available very inexpensively as racemic mixtures, and kinetic resolution is an attractive strategy for the production of optically active epoxides, given an economical and operationally simple method. Readily accessible synthetic catalysts (chiral cobalt-based salen complexes) have been used for the efficient asymmetric hydrolysis of terminal epoxides. This process uses water as the only reagent, no added solvent, and low loadings of a recyclable catalyst (<0.5 mole percent), and it affords highly valuable terminal epoxides and 1,2-diols in high yield with high enantiomeric enrichment..
13. A. Zamojski, F. Kakiuchi, R. G. Konsler, J. F. Larrow, Makoto Tokunaga, Enantioselective catalytic ring opening of epoxides with carboxylic acids, Chemtracts, 1998.04.
14. Makoto Tokunaga, Yasuo Wakatsuki, The first anti-Markovnikov hydration of terminal alkynes
Formation of aldehydes catalyzed by a ruthenium (II)/Phosphane mixture
, Angewandte Chemie - International Edition, 10.1002/(SICI)1521-3773(19981102)37:20<2867::AID-ANIE2867>3.0.CO;2-E, 1998.11.
15. J. D. Schloss, L. A. Paquette, E. Jacobsen, Makoto Tokunaga, J. Larrow, F. Kakiuchi, E. Jacobsen, Total synthesis of muconin by efficient assembly of chiral building blocks, Chemtracts, 1999.04.
16. Makoto Tokunaga, Markus Eckert, Yasuo Wakatsuki, Ruthenium-catalyzed intermolecular hydroamination of terminal alkynes with anilines
A practical synthesis of aromatic ketimines
, Angewandte Chemie - International Edition, 10.1002/(SICI)1521-3773(19991102)38:21<3222::AID-ANIE3222>3.0.CO;2-7, 1999.11.
17. Makoto Tokunaga, Yasuo Wakatsuki, Addition reactions to alkynes catalyzed by ruthenium complexes, Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry, 10.5059/yukigoseikyokaishi.58.587, 2000.01, Additions to C-C multiple bonds are simple and the most efficient methods in organic synthesis in terms of atom utilization due to avoidance of stoichiometric amounts of by-products. The following catalytic C-C, C-O and C-N bond-constructions by direct additions of nucleophiles to alkynes catalyzed by ruthenium complexes have been developed. 1) Dimerization of terminal alkynes to 1,4-disubstituted butatriens which is an unusual tail-to-tail coupled product. 2) The first example of anti-Markovnikov hydration of terminal alkynes to aldehydes. 3) Intermolecular hydroamination of terminal alkynes with anilines to imines. Some of the reactions proceed in high yields under solvent-free, open-air conditions. Theoretical studies were also performed about transformation of η2-coordinated 1-alkynes to vinylidene complexes which plays important role in regioselectivity of the addition reactions..
18. Toshiaki Suzuki, Makoto Tokunaga, Yasuo Wakatsuki, Ruthenium complex-catalyzed anti-Markovnikov hydration of terminal alkynes, Organic Letters, 10.1021/ol0003937, 2001.03, Highly regioselective, efficient, and substituent-tolerant anti-Markovnikov hydration of terminal alkynes occurs to give n-aldehyde by use of a catalytic amount of easily available cyclopentadienylruthenium complexes bearing appropriate bidentate or monodentate phosphme ligands. Typically, RuCpCl(dppm) (1 mol %) catalyzes the addition of water to 1-hexyne at 100°C to give hexanal in 95% yield: 2-hexanone is not detected at all..
19. Makoto Tokunaga, Mitsuru Ota, Masa aki Haga, Yasuo Wakatsuki, A practical one-pot synthesis of 2,3-disubstituted indoles from unactivated anilines, Tetrahedron Letters, 10.1016/S0040-4039(01)00588-3, 2001.06, 2-Substituted-3-methyl indoles are synthesized with good regioselectivity from readily available substrates and catalysts, i.e. the reaction of anilines with propargyl alcohols in the presence of 0.36-1 mol% Ru3(CO)12..
20. Makoto Tokunaga, T. Suzuki, N. Koga, T. Fukushima, A. Horiuchi, Y. Wakatsuki, Ruthenium-catalyzed hydration of 1-alkynes to give aldehydes
Insight into anti-Markovnikov regiochemistry
, Journal of the American Chemical Society, 10.1021/ja0119292, 2001.12, The mechanism of the selective conversion of 1-alkynes to aldehydes by hydration was investigated by isolating organic and organometallic byproducts, deuterium-labeling experiments, and DFT calculations. The D-labeled acetylenic hydrogen of 1-alkyne was found exclusively in the formyl group of the resulting aldehydes. After the reaction, the presence of metal-coordinated CO was confirmed. All of the experimental results strongly suggest the involvement of a metal-acyl intermediate with the original acetylenic hydrogen also bound to the metal center as a hydride, with the next step being release of aldehyde by reductive elimination. Theoretical analyses suggest that the first step of the catalytic cycle is not oxidative addition of acetylene C-H or tautomerization of η2-alkyne to a vinylidene complex, but rather protonation of the coordinated 1-alkyne at the substituted carbon to form a metal-vinyl intermediate. This cationic intermediate then isomerizes to Ru(IV)-hydride-vinylidene via α-hydride migration of the vinyl group to the metal center, followed by attack of the vinylidene α-carbon by OH- to give the metal-hydride-acyl intermediate..
21. Yasushi Tsuji, Makoto Tokunaga, Yasushi Obora, Recent progress in supramolecular transition metal catalysis, Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry, 10.5059/yukigoseikyokaishi.60.942, 2002.01, Recent progress in supramolecular transition metal catalysis is described. Various supramolecular catalyst systems containing cyclodextrins, dendrimers, calixarenes, and other moieties published in 1999-2002 are reviewed..
22. Scott E. Schaus, Bridget D. Brandes, Jay F. Larrow, Makoto Tokunaga, Karl B. Hansen, Alexandra E. Gould, Michael E. Furrow, Eric N. Jacobsen, Highly selective hydrolytic kinetic resolution of terminal epoxides catalyzed by chiral (salen)CoIII complexes. Practical synthesis of enantioenriched terminal epoxides and 1,2-diols, Journal of the American Chemical Society, 10.1021/ja016737l, 2002.02, The hydrolytic kinetic resolution (HKR) of terminal epoxides catalyzed by chiral (salen)CoIII complex 1·OAc affords both recovered unreacted epoxide and 1,2-diol product in highly enantioenriched form. As such, the HKR provides general access to useful, highly enantioenriched chiral building blocks that are otherwise difficult to access, from inexpensive racemic materials. The reaction has several appealing features from a practical standpoint, including the use of H2O as a reactant and low loadings (0.2-2.0 mol %) of a recyclable, commercially available catalyst. In addition, the HKR displays extraordinary scope, as a wide assortment of sterically and electronically varied epoxides can be resolved to ≥ 99% ee. The corresponding 1,2-diols were produced in good-to-high enantiomeric excess using 0.45 equiv of H2O. Useful and general protocols are provided for the isolation of highly enantioenriched epoxides and diols, as well as for catalyst recovery and recycling. Selectivity factors (krel) were determined for the HKR reactions by measuring the product ee at ca. 20% conversion. In nearly all cases, krel values for the HKR exceed 50, and in several cases are well in excess of 200..
23. Yasushi Obora, Masafumi Nakanishi, Makoto Tokunaga, Yasushi Tsuji, Palladium complex catalyzed acylation of allylic esters with acylstannanes
Complementary method to the acylation with acylsilanes
, Journal of Organic Chemistry, 10.1021/jo0202482, 2002.08, Palladium-catalyzed acylation of allylic trifluoroacetates (2) using acylstannanes (1) is reported. The reaction serves as a complementary method to the previously reported acylation with acylsilane (4). In particular, the reaction is profitable in the acylation of unsubstituted allyl trifluoroacetate (2a) and benzoylation of allylic trifluoroacetates to afford synthetically useful β,γ-unsaturated ketones (3) in good yields without undesirable isomerizations..
24. Yasushi Obora, Angelo S. Baleta, Makoto Tokunaga, Yasushi Tsuji, Platinum complex catalyzed reaction of tributyltin cyanide with alkynes, Journal of Organometallic Chemistry, 10.1016/S0022-328X(02)01855-7, 2002.10, In the presence of a catalytic amount (5 mol%) of a platinum complex, tributyltin cyanide (1) reacts with dimethyl- (2a) or diethyl acetylenedicarboxylate (2b) to afford cyanostannylation adducts (3a, b) in excellent yields. The reaction proceeds highly selectively affording only a (Z)-isomer. The compounds 3a, b are novel products which possess synthetically useful cyano, alkenylstannyl and alkoxycarbonyl functionalities in the same molecule. Two alkoxycarbonyl functionalities may be indispensable on each alkyne carbon to accomplish the cyanostannylation reaction. Reaction with terminal alkynes gave the stannylated product (6)..
25. Toshiaki Suzuki, Makoto Tokunaga, Yasuo Wakatsuki, Efficient transformation of propargylic alcohols to α,β-unsaturated aldehydes catalyzed by ruthenium/water under neutral conditions, Tetrahedron Letters, 10.1016/S0040-4039(02)01821-X, 2002.10, α,β-Unsaturated aldehydes were selectively obtained in high yields from propargylic alcohols in aqueous solutions using RuCpCl(PR3)2 (Cp=η5-C5H5) as a catalyst. Of the tert-phosphine ligands examined, PMe3 gave the most satisfactory results. Typically, RuCpCl(PMe3)2 (5 mol%) catalyzed the transformation of oct-1-yn-3-ol at 100°C to give 2-octenal in an isolated yield of 85% (E/Z=80/20)..
26. Yasuo Wakatsuki, Zhaomin Hou, Makoto Tokunaga, New reactions of 1-alkynes catalyzed by transition metal complexes, Chemical Record, 10.1002/tcr.10061, 2003, Recently discovered catalytic reactions with ruthenium and lanthanide metal complexes have extended the scope of 1-alkynes as useful reagents. The specific formation of aryl-substituted (Z)-1,3-enynes via the dimerization of HC≡CR 1 (R 1 = aryl) has been attained using dimeric lanthanide complexes, the catalytic activity of which appears to be unaffected by time. The dimerization of HC≡CR 2 (R 2 = t-Bu, SiMe 3) catalyzed by Ru(cod)(cot)/PR 3 or RuH 2(PPh 3) 3 produces a good yield of butatrienes (Z)-R 2CH=C=C=CHR 2 with a high degree of selectivity. Under certain conditions, HC≡C-SiMe 3 dimerizes to yield exclusively (Z)-M 3Si-C≡C-CH= CH-SiMe 3. The hydration of HC≡CR 3 (R 3 = alkyl, aryl) catalyzed by RuCl 2/PR′ 3 or CpRuCl(PR″ 3) 2 has realized the first example of anti-Markovnikov regioselectivity in an addition reaction of water that produces aldehydes R 3CH 2-CHO. The application of this reaction to propargylic alcohols has lead to their formal isomerization to α,β-unsaturated aldehydes. In contrast, the addition of amines R 4-NH 2 (R 4 = aryl) to HC≡CR 5 (R 5 = alkyl, aryl) conforms to Markovnikov's rule to produce ketimines R 5-(C=NR 4)-CH 3 when catalyzed by a Ru 3(CO) 12/additive. Since the reaction can be performed in air without the need for any solvents, it enables the practical synthesis of aromatic ketimines, which are difficult to prepare by conventional methods. The synthesis of indoles using deactivated anilines is one practical application of this reaction. The mechanisms of some of these reactions have been analyzed in detail with the aid of theoretical calculations..
27. Osamu Niyomura, Makoto Tokunaga, Yasushi Obora, Tetsuo Iwasawa, Yasushi Tsuji, Rate enhancement with a bowl-shaped phosphane in the rhodium-catalyzed hydrosilylation of ketones, Angewandte Chemie - International Edition, 10.1002/anie.200390331, 2003.03, Up to 154-fold rate enhancement (see picture) and higher yields are achieved with the bowl-shaped triarylphosphane ligand P(tm-tp)3 compared with common phosphane ligands in Rh-catalyzed hydrosilylation of ketones. The superior performance of P(tm-tp)3 over the similar P(tp)3 is apparently related to the deeper bowl formed by the methyl-bearing terphenyl substituents in the former..
28. Yasushi Obora, Hiroyuki Moriya, Makoto Tokunaga, Yasushi Tsuji, Cross-coupling reaction of thermally stable titanium(II)-alkyne complexes with aryl halides catalysed by a nickel complex, Chemical Communications, 2003.11, The first cross-coupling reaction of thermally stable titanium(II)-alkyne complexes with aryl iodides in the presence of a catalytic amount of Ni(cod)2 is presented..
29. Hiroshi Aoyama, Makoto Tokunaga, Shin Ichiro Hiraiwa, Yuki Shirogane, Yasushi Obora, Yasushi Tsuji, Hydrolysis of Alkenyl Esters and Ethers Catalyzed by Metal Complexes, Organic Letters, 10.1021/ol036228j, 2004.02, (Equation presented) Various kinds of transition metals catalyzed the hydrolysis of alkenyl esters and ethers under buffer-free, high concentration conditions compared to usual biocatalysts. Hydrolytic kinetic resolution of cis-2-tert-butylcyclohexyl vinyl ether was achieved by chiral (salen)Co complexes with good selectivity (krel = 10.0)..
30. Tetsuo Iwasawa, Makoto Tokunaga, Yasushi Obora, Yasushi Tsuji, Homogeneous palladium catalyst suppressing Pd black formation in air oxidation of alcohols, Journal of the American Chemical Society, 10.1021/ja031936l, 2004.06, In homogeneous catalyst systems, there is the persistent problem that metal aggregation and precipitation cause catalyst decomposition and considerable loss of catalytic activity. Pd black formation is a typical example. Pd catalysts are known to easily aggregate and form Pd black, although they realize a wide variety of useful reactions in organic synthesis. In order to overcome this intrinsic problem of homogeneous Pd catalysis, we explored a new class of Pd catalyst by adopting aerobic oxidation of alcohols as a probe reaction. Herein we report a new catalyst system that suppresses the Pd black formation even under air and with a high substrate to catalyst molar ratio (S/C: more than 1000) in oxidation of alcohols. The novel pyridine derivatives having a 2,3,4,5-tetraphenylphenyl substituent and its higher dendritic unit at the 3-position of the pyridine ring were found to be excellent ligands with Pd(OAc)2 in the palladium-catalyzed air (balloon) oxidation of alcohols in toluene at 80 °C. Comparison with structurally related pyridine ligands revealed that introduction of the 2,3,4,5-tetraphenylphenyl substituent at the 3-position of pyridine ring effectively suppresses the Pd black formation, maintaining the catalytic activity for a long time to give aldehydes or ketones as products in high yields..
31. Makoto Tokunaga, Utilization of water as a reagent in regio- and stereoselective reactions, Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry, 10.5059/yukigoseikyokaishi.63.18, 2005.01, Utilization of water as a reagent as well as a solvent is an important topic in synthetic organic chemistry. This article describes recent progress of hydration and hydrolysis reactions catalyzed by transition metal complexes. Direct transformation of 1-alkynes into aldehydes by Ru (II)-catalyzed hydration has been developed. It has been long known as a textbook example that the hydration follows Markovnikov's rule to give ketones as a sole product. Mechanistic study of the transformation revealed that Ru(II)-vinylidene complexes presumably are not involved in the current hydration reaction, but Ru(IV)-hydride-vinylidene complexes are concerned. Ru (II)-catalyzed hydroamination and its application to heterocycle synthesis are also described. This paper also illustrates metal catalyzed hydrolysis of terminal epoxides, alkenyl esters and ethers. Hydrolytic kinetic resolution of some chiral terminal epoxides and vinyl ethers are also developed..
32. Yasushi Obora, Yun Kui Liu, Li Hong Jiang, Kazuhiro Takenaka, Makoto Tokunaga, Yasushi Tsuji, Iridium(I) and rhodium(I) cationic complexes with triphosphinocalix[6] arene ligands
Dynamic motion with size-selective molecular encapsulation
, Organometallics, 10.1021/om049227j, 2005.01, A novel capsule-shaped Ir(I) and Rh(I) cationic complexes with a triphosphinocalix[6]arene as a ligand were synthesized. These complexes showed dynamic behavior with size-selective molecular encapsulation, which was confirmed by variable-temperature 31P{1H} NMR measurement in the presence of various molecules..
33. Yasushi Obora, Masahiro Kimura, Makoto Tokunaga, Yasushi Tsuji, Low-valent Nb(III)-mediated synthesis of 1,1,2-trisubstituted-1H-indenes from aliphatic ketones and aryl-substituted alkynes, Chemical Communications, 10.1039/b412519c, 2005.02, A variety of 1,1,2-trisubstituted-1H-indenes are synthesized by the reaction of aliphatic ketones, aryl-substituted alkynes and NbCl 3(DME) in 1,2-dichloroethane under reflux conditions..
34. Osamu Niyomura, Tetsuo Iwasawa, Naoki Sawada, Makoto Tokunaga, Yasushi Obora, Yasushi Tsuji, A bowl-shaped phosphine as a ligand in rhodium-catalyzed hydrosilylation
Rate enhancement by a mono(phosphine) rhodium species
, Organometallics, 10.1021/om0503491, 2005.07, Bowl-shaped phosphine (BSP) ligands markedly accelerated the rhodium-catalyzed hydrosilylation of ketones and ketimines as compared with the effect of conventional phosphine ligands such as PPh 3 and P(t-Bu) 3. 31P NMR study of a mixture of [RhCl(C 2H 4) 2] 2 and phosphines at various P/Rh ratios revealed that coordination of BSP to the rhodium metal was successfully regulated, and the resultant rhodium complex bearing only one phosphine ligand (a mono(phosphine) rhodium species) was responsible for the acceleration. Structural comparison between BSP and the conventional phosphines was carried out using HF/6-31G(d)-CONFLEX/MM3-optimized structures. The mono(phosphine) rhodium complex having 1,5-cyclooctadiene as a ligand was isolated, and its X-ray molecular structure was determined..
35. Hiroshi Aoyama, Makoto Tokunaga, Junya Kiyosu, Tetsuo Iwasawa, Yasushi Obora, Yasushi Tsuji, Kinetic resolution of axially chiral 2,2′-dihydroxy-1,1′- biaryls by palladium-catalyzed alcoholysis, Journal of the American Chemical Society, 10.1021/ja051750h, 2005.08, Palladium-diamine complexes catalyzed kinetic resolution of axially chiral 2,2′-dihydroxy-1,1′-biaryls by alcoholysis of vinyl ethers. The reaction proceeded with high selectivity for various kinds of biaryls. This process is applicable to not only binaphthols but also biphenols, which have been considered to be difficult for the enantioselective synthesis by known catalytic methods..
36. Tetsuaki Fujihara, Yasushi Obora, Makoto Tokunaga, Hiromichi Sato, Yasushi Tsuji, Dendrimer N-heterocyclic carbene complexes with rhodium(I) at the core, Chemical Communications, 10.1039/b506927k, 2005.09, Novel dendrimer N-heterocyclic carbene complexes with rhodium(I) located at the core were synthesized, and a positive dendrimer effect was found in the hydrosilylation of ketones catalyzed by them..
37. Tomoko Komano, Tetsuo Iwasawa, Makoto Tokunaga, Yasushi Obora, Yasushi Tsuji, MALDI TOF mass study on oligomerization of Pd(OAc)2(L) 2 (L = Pyridine derivatives)
Relevance to Pd black formation in Pd-catalyzed air oxidation of alcohols
, Organic Letters, 10.1021/ol051845o, 2005.10, (Chemical Equation Presented) Oligomerization of Pd(OAc) 2(L)2 (L = pyridine derivatives), a catalyst for the air oxidation of alcohols, is studied with MALDI TOF mass, using dithranol as the matrix. The degree of the Pd oligomerization is influenced by the pyridine ligands, and this ligand effect is similar to one observed for Pd black formation in the catalysis..
38. Makoto Tokunaga, Yuki Shirogane, Hiroshi Aoyama, Yasushi Obora, Yasushi Tsuji, Copper-catalyzed oxidative cleavage of carbon-carbon double bond of enol ethers with molecular oxygen, Journal of Organometallic Chemistry, 10.1016/j.jorganchem.2005.05.018, 2005.11, A novel CC bond cleavage reaction of aromatic enol ethers (1) to give ketones (2) using molecular oxygen as oxidant is described. Among the examined catalysts (Cu(II), Pd(II), Ru(II), and H+), CuCl2 exhibited the highest activity. The reaction proceeded smoothly with several kinds of substrates..
39. Yasushi Obora, Makoto Tokunaga, Yasushi Tsuji, Transition-metal complexes with nano-sized phosphine and pyridine ligands-catalysis, fluxional behavior and molecular recognition, Catalysis Surveys from Asia, 10.1007/s10563-005-9160-5, 2005.12, Nano-sized phosphine and pyridine ligands having tetraphenylphenyl-, m-terphenyl-, poly(benzylether) moieties were synthesized. These ligands showed a remarkable effect on homogeneous transition metal catalyzed reactions. Pd(II) complexes with tetraphenylphenyl substituted pyridine ligands show high catalytic activities for oxidation of ketones suppressing Pd black formation and maintains the catalytic activity for a long time. Rh(I) complex catalysts with m-terphenyl substituted phosphine ligands showed remarkable rate acceleration in the hydrosilylation of ketones. In addition, several phosphinocalixarene ligands were synthesized and their coordination studies with Pd(II), Pt(II), Ru(II), Ir(I), and Rh(I) metals were documented. Ir(I) and Rh(I) cationic complexes with a 1,3,5-triphosphinocalix[6]arene ligand showed dynamic behavior with size-selective molecular recognition..
40. Yasushi Obora, Kui Liu Yun, Sho Kubouchi, Makoto Tokunaga, Yasushi Tsuji, Monophosphanylcalix[6]arene ligands
Synthesis characterization, complexation, and their use in catalysis
, European Journal of Inorganic Chemistry, 10.1002/ejic.200500673, 2006.01, Novel phosphanylcalix[6]arenes having mono-O-diphenylphosphanylmethyl (3) and mono-O-(4-diphenylphosphanylphenyl)methyl substituents (5) have been synthesized. The structures of these monophosphanylcalix[6]arenes were determined by NMR spectroscopy, mass spectrometry, and X-ray crystal structure analysis. The X-ray structure reveals that 3 adopts a flattened 1,2,3-alternate conformation in the crystalline state, while the NMR spectra show that 3 and 5 have a cone conformation in solution. Structure optimization and energy calculations for 3 and 5 at the B3LYP/LANL2DZ-CONFLEX5/MMFF94s level of theory show that the cone conformation is slightly more stable than the 1,2,3-alternate conformation by 0.36 kcal mol-1 for 3 and 0.96 kcal mol-1 for 5. Complexation of 3 with [PtCl2(COD)] and [Rh(COD) 2]BF4 gives cis-coordinated [PtCl2(3) 2] and [Rh(COD)(3)2]BF4, respectively. The X-ray analysis of [PtCl2(3)2] shows that 3 adopts a cone conformation upon complexation. Combination of 3 and 5 with [Rh(COD) 2]BF4 provides an active catalyst for the hydroformylation of a variety of terminal alkenes..
41. Yasushi Obora, Masahiro Kimura, Toshiyuki Ohtake, Makoto Tokunaga, Yasushi Tsuji, Nickel-catalyzed cross-coupling reaction of niobium(III)-alkyne complexes with aryl iodides, Organometallics, 10.1021/om060065w, 2006.04, Nickel-catalyzed cross-coupling reactions of Nb(III)-alkyne complexes with aryl iodides are reported, in which addition of lithium alkoxide is indispensable and diarylated coupling products are afforded as products..
42. Makoto Tokunaga, Junya Kiyosu, Yasushi Obora, Yasushi Tsuji, Kinetic resolution displaying zeroth order dependence on substrate consumption
Copper-catalyzed asymmetric alcoholysis of azlactones
, Journal of the American Chemical Society, 10.1021/ja058112j, 2006.04, Kinetic resolution of 4-alkyl-2-aryl-5-oxo-4,5-dihydrooxazole-4-carboxylic acid esters (azlactones 1) were achieved by copper-DTBM-SEGPHOS catalyzed alcoholysis reaction with good selectivity (12 examples). Variation of ee of unreacted substrates 1 and products 2 with conversion was found to follow the theoretical line of zeroth-order kinetic resolution, for which the selectivity profiles and graphical analysis were presented for the first time. The efficiency of resolution in zeroth-order reaction is higher than first-order reaction. For example, the reaction with 1a afforded (S)-1a (99% ee) and (R)-2a (74% ee) at 57% conversion, where the krel values were calculated to be 6.7 as zeroth-order kinetic resolution and 37 as first-order kinetic resolution..
43. Tetsuo Iwasawa, Tomoko Komano, Atsunori Tajima, Makoto Tokunaga, Yasushi Obora, Tetsuaki Fujihara, Yasushi Tsuji, Phosphines having a 2,3,4,5-tetraphenylphenyl moiety
Effective ligands in palladium-catalyzed transformations of aryl chlorides
, Organometallics, 10.1021/om060615q, 2006.09, Three new triarylphosphines were prepared that have a 2,3,4,5- tetraphenylphenyl (TPPh) moiety on one of the phenyl rings (at the ortho, meta, or para position) of triphenylphosphine. Among them, the ortho derivative is particularly effective to utilize unactivated aryl chlorides in three different palladiumcatalyzed reactions, i.e., Suzuki-Miyaura coupling, Mizoroki-Heck reaction, and silylation with Me3SiSiMe3. On the other hand, the corresponding meta and para derivatives are not effective as ligands at all in these catalytic reactions. X-ray crystal structures of Pd(0) complexes having the effective phosphines (ortho derivatives) as ligands show that η2-coordination on the TPPh moiety is general and operative to realize a highly active catalyst system..
44. Makoto Tokunaga, Hiroshi Aoyama, Yuki Shirogane, Yasushi Obora, Yasushi Tsuji, Oxidative cleavage of C{single bond}C bond of 2-phenylpropionaldehyde using molecular oxygen, Catalysis Today, 10.1016/j.cattod.2006.05.020, 2006.09, Oxidative C{single bond}C bond cleavage between carbonyl carbon and vicinal carbon of 2-phenylpropionaldehyde to give acetophenone using 1 atm molecular oxygen as oxidant was catalyzed by Ce(IV), V(IV) and Brønsted acids. Among the examined catalysts, sulfuric acid exhibited the highest activity and gave the product in 99% yield..
45. Toshiaki Murai, Shinsuke Inaji, Ken Morishita, Fumitoshi Shibahara, Makoto Tokunaga, Yasushi Obora, Yasushi Tsuji, Synthesis of 1,1′-binaphthyl-2,2′-diyl phosphoroselenoic amides and their conversion to optically pure phosphoramidites, Chemistry Letters, 10.1246/cl.2006.1424, 2006.12, Optically pure phosphoroselenoyl chloride was reacted with racemic amines to give phosphoroselenoic amides as two diastereomeric mixtures in high yields. The diastereomeric mixtures were separated by fractional recrystallization or by chromatography. Extrusion of the selenium atom from the separated amides led to diastereomerically pure phosphoramidites. The ability of the obtained amidites to act as optically active ligands was tested in the hydrogenation of an imine..
46. Tetsuaki Fujihara, Yasushi Obora, Makoto Tokunaga, Yasushi Tsuji, Rhodium(iii) complexes with a bidentate N-heterocyclic carbene ligand bearing flexible dendritic frameworks, Dalton Transactions, 10.1039/b701104k, 2007, Rh(iii) complexes with a bidentate N-heterocyclic carbene ligand bearing flexible dendritic frameworks have been synthesized and fully characterized by X-ray crystallographic analysis, NMR measurements and theoretical calculations..
47. Hiromichi Sato, Tetsuaki Fujihara, Yasushi Obora, Makoto Tokunaga, Junya Kiyosu, Yasushi Tsuji, Rhodium(I) complexes with N-heterocyclic carbenes bearing a 2,3,4,5-tetraphenylphenyl and its higher dendritic frameworks, Chemical Communications, 10.1039/b612385f, 2007, Novel rhodium(i) complexes with N-heterocyclic carbenes bearing a 2,3,4,5-tetraphenylphenyl and its higher dendritic frameworks were synthesized and the complexes were used as catalysts in rhodium-catalyzed hydrosilylation of α,β-unsaturated ketones to show high 1,4-adduct selectivity..
48. Makoto Tokunaga, Hiroshi Aoyama, Junya Kiyosu, Yuki Shirogane, Tetsuo Iwasawa, Yasushi Obora, Yasushi Tsuji, Metal complexes-catalyzed hydrolysis and alcoholysis of organic substrates and their application to kinetic resolution, Journal of Organometallic Chemistry, 10.1016/j.jorganchem.2006.06.045, 2007.01, Metal complexes-catalyzed hydrolysis and alcoholysis of organic substrates such as alkenyl esters, alkenyl ethers, and azlactones (oxazol-5(4H)-ones) are described. These reactions were applied for kinetic resolution of chiral compounds and high selectivities were achieved with vinyl ethers of 2-substituted cyclohexanols, 1,1′-bi-2-naphthols, 1,1′-bi-2-phenols, and 4,4-disubstituted azlactones. Oxidative carbon-carbon bond cleavage reactions, which were found in the course of the study of asymmetric hydrolysis were also described..
49. Hidetoshi Ohta, Makoto Tokunaga, Yasushi Obora, Tomohiro Iwai, Tetsuo Iwasawa, Tetsuaki Fujihara, Yasushi Tsuji, A bowl-shaped phosphine as a ligand in palladium-catalyzed Suzuki-Miyaura coupling of aryl chlorides
Effect of the depth of the bowl
, Organic Letters, 10.1021/ol0626138, 2007.01, (Chemical Equation Presented) Bowl-shaped phosphine ligands were found to be highly effective in Suzuki-Miyaura coupling of unactivated aryl chlorides, in which the depth of the bowl affected the catalytic activity considerably..
50. Tetsuaki Fujihara, Yasushi Obora, Makoto Tokunaga, Yasushi Tsuji, Rhodium(iii) complexes with a bidentate N-heterocyclic carbene ligand bearing flexible dendritic frameworks, Journal of the Chemical Society. Dalton Transactions, 10.1039/b701104k, 2007.03, Rh(iii) complexes with a bidentate N-heterocyclic carbene ligand bearing flexible dendritic frameworks have been synthesized and fully characterized by X-ray crystallographic analysis, NMR measurements and theoretical calculations..
51. Makoto Tokunaga, Saki Harada, Tetsuo Iwasawa, Yasushi Obora, Yasushi Tsuji, Palladium-catalyzed oxidation of cyclohexanones to conjugated enones using molecular oxygen, Tetrahedron Letters, 10.1016/j.tetlet.2007.07.181, 2007.09, Oxidation of cyclohexanones into conjugated enones with molecular oxygen as oxidant was achieved by palladium catalysts. A catalyst system consists of 1 mol % Pd(OCOCF3)2 and 5,5′-dimethyl-2,2′-bipyridine accomplished maximum 84% yield for the oxidation of cyclohexanone and 51-78% yields for 4-substituted-cyclohexanones..
52. Xiaohao Liu, Masatake Haruta, Makoto Tokunaga, Coprecipitated gold-trieobalt tetraoxide catalyst for heterogeneous hydroformylation of oleflns, Chemistry Letters, 10.1246/cl.2008.1290, 2008, The combination of gold (Au 0) and tricobalt tetraoxide (CO 3O 4) prepared by coprecipitation gives high-performance heterogeneous catalysts for hydroformylation reaction with selectivity above 85% in desired aldehydes, although neither Au 0 nor CO 3O 4 have been demonstrated in this reaction and show poor activities. The A11/CO 3O 4 catalysts can be recycled by simple decantation with slight decrease in catalytic activity along with recycle times. The role of Au may mainly promote in situ reduction of CO 3O 4 to Co 0 catalyzing the hydroformylation reaction..
53. Akiyuki Hamasaki, Xiaohao Liu, Makoto Tokunaga, Amidoearbonylation of aldehydes utilizing cobalt oxide-supported gold nanoparticles as a heterogeneous catalyst, Chemistry Letters, 10.1246/cl.2008.1292, 2008, Cobalt oxide-supported gold-nanoparticles-catalyzed transformation of aldehydes and their equivalents to N-acyl-α-arnino acids was achieved. The desired products were obtained in moderate to excellent yields under milder reaction conditions than previous reports employing octacarbonyldicobalt as a catalyst..
54. Aki Nakamura, Makoto Tokunaga, Au(I) complexes-catalyzed transfer vinylation of alcohols and carboxylic acids, Tetrahedron Letters, 10.1016/j.tetlet.2008.04.037, 2008.06, Au(I) complexes-catalyzed transfer vinylation of alcohols and carboxylic acids has been achieved. The catalyst system consists of 2 mol % AuClPPh3 and 2 mol % AgOAc. Primary alcohols and secondary alcohols were converted into corresponding vinyl ethers in good yield (64-93%); however, tertiary alcohols showed poor reactivities. Carboxylic acids were also transformed into corresponding vinyl esters in good yield (78-96%)..
55. Takeshi Sakuma, Eiji Yamamoto, Hiroshi Aoyama, Yasushi Obora, Yasushi Tsuji, Makoto Tokunaga, Kinetic resolution of phosphoryl and sulfonyl esters of 1,1′-bi-2-naphthol via Pd-catalyzed alcoholysis of their vinyl ethers, Tetrahedron Asymmetry, 10.1016/j.tetasy.2008.06.034, 2008.07, Kinetic resolution of phosphoryl and sulfonyl esters of 1,1′-bi-2-naphthol has been achieved via the Pd-catalyzed alcoholysis of their vinyl ethers. The highest krel value reached 36.8 with substrate 3c, and (R)-3c 99.0% ee was obtained in 43% isolated yield..
56. Naoya Ohmura, Asami Nakamura, Akiyuki Hamasaki, Makoto Tokunaga, Hydrolytic deallylation of N-allyl amides catalyzed by PdII complexes, Liebigs Annalen der Chemie, 10.1002/ejoc.200800771, 2008.10, Hydrolytic deallylation of N-allyl amides to give amides and propanal can be achieved with PdII catalysts. The optimized catalyst consists of Pd(OCOCF3)2 and 1,3-bis(diphenylphosphanyl) propane (DPPP). Several kinds of open-chain N-allyl amides and N-allyl lactams undergo hydrolytic deallylation to give the corresponding amides and lactams in good to high yield. A mechanism which includes isomerization to enamides and subsequent hydrolysis is proposed..
57. Yoshihiro Yamane, Xiaohao Liu, Akiyuki Hamasaki, Tamao Ishida, Masatake Haruta, Takushi Yokoyama, Makoto Tokunaga, One-Pot synthesis of indoles and aniline derivatives from nitroarenes under hydrogénation condition with supported gold nanoparticles, Organic Letters, 10.1021/ol902061j, 2009, One-pot sequences of hydrogenation/hydroamination to form indoles from (2-nitroaryl)alkynes and hydrogenation/reductive amination to form aniline derivatives from nitroarenes and aldehydes were catalyzed by Au nanoparticles supported on Fe2O3. Nitro group selective hydrogenations and successive reactions were efficiently catalyzed under the conditions..
58. Hisashi Itoh, Eiji Yamamoto, Shigeyuki Masaoka, Ken Sakai, Makoto Tokunaga, Kinetic resolution of P-Chirogenic compounds by palladium-catalyzed alcoholysis of vinyl ethers, Advanced Synthesis and Catalysis, 10.1002/adsc.200900304, 2009.08, The palladium-catalyzed asymmetric alcoholysis of vinyl ethers of P-chirogenic compounds has been achieved. The kinetic resolution of aryl tert-butyl(2-vinyloxyaryl)phosphinates was catalyzed by palladium/chiral diamine complexes with high selectivities (krel: 12-196)..
59. Tetsuaki Fujihara, Sho Kubouchi, Yasushi Obora, Makoto Tokunaga, Kazuhiro Takenaka, Yasushi Tsuji, Synthesis and structural characterization of a series of mono-O-(diphenylphosphinobenzyl)calix[6]arenes with and without tert-butyl moieties at the upper rim, Bulletin of the Chemical Society of Japan, 10.1246/bcsj.82.1187, 2009.10, abs Synthesis and characterization of a series of mono-O- (diphenylphosphinobenzyl)calix[6]arenes are presented. The two types of calix[6]arene moieties were prepared: 1 (with tert-butyl groups at the upper rim) and 2 (without the tert-butyl groups). With regard to the position of a phosphorus atom, the diphenylphosphino group was introduced onto the ortho, meta, or para positions with the benzyl ether moiety. These phosphines as well as their oxides were fully characterized by elemental analysis, NMR measurements, and HR-ESI-MS. The NMR study indicated that 1 had a cone conformation whereas 2 was very flexible in solution. These phosphines were found to be effective ligands in Rh-catalyzed hydroformylation..
60. Xiaohao Liu, Baoshan Hu, Kaoru Fujimoto, Masatake Haruta, Makoto Tokunaga, Hydroformylation of olefins by Au/Co3O4 catalysts, Applied Catalysis B: Environmental, 10.1016/j.apcatb.2009.08.021, 2009.11, The hydroformylation of olefins over supported gold catalysts in an autoclave reactor under mild conditions (100-140 °C, 3-5 MPa) has been studied. Over Au/AC (activated carbon), Au/PVP (polyvinylpyrrolidone), Au/Al2O3, Au/TiO2, Au/Fe2O3, Au/ZnO, Au/CeO2 and Co3O4, 1-olefin mainly remained unchanged and the major products were isomerized olefins or hydrogenated paraffin. In contrast, Au nanoparticles deposited on Co3O4 led to remarkably high catalytic activities in hydroformylation reaction with selectivities above 85% to desired aldehydes. The hydroformylation of olefins proceeds preferentially at temperatures below 140 °C, above which the reactions of olefins gradually shifted to isomerization and then to hydrogenation. It appeared that the activity and selectivity of hydroformylation reaction strongly depend on the molecular structure of olefins, which could be ascribed to steric constraints as internal olefins are relatively inappropriate to form alkyl group and subsequent acyl group by insertion of CO. The Au/Co3O4 catalyst can be recycled by simple decantation with slight decrease in catalytic activity along with an increase in recycle times, which is a great advantage over homogeneous catalysts. The role of gold nanoparticles can be assumed to dissociate hydrogen molecule into atomic species which reduce Co3O4 to Co metal under mild reaction conditions..
61. Toshifumi Hirai, Aklyuki Hamasaki, Aki Nakamura, Makoto Tokunaga, Enhancement of reaction efficiency by functionalized alcohols on gold(I)-catalyzed intermodular hydroalkoxylation of unactivated olefins, Organic Letters, 10.1021/ol9023166, 2009.12, "Chemical Equation Presented" Intermolecular hydroalkoxylation of unactivated olefins catalyzed by the combination of gold(I) and electron deficient phosphine ligands has been developed. Although pairings of unactivated olefins and common aliphatic alcohols gave unsatisfactory results In gold catalyzed hydroalkoxylations, the use of alcohol substrates bearing coordination functionalities such as halogen or alkoxy groups showed great improvement of reactivity..
62. Makoto Tokunaga, Akiyuki Hamasaki, Eiji Yamamoto, Hisashi Itoh, Metal complexes-catalyzed hydrolysis, alcoholysis, and hydroalkoxylation, Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry, 10.5059/yukigoseikyokaishi.68.738, 2010.07, In this accounts, we describe our recent studies on hydrolysis, alcoholysis, and addition of alcohols to organic molecules. The reactions utilizing water and alcohols as a reagent are one of the most basic and simple reactions. The palladium-catalyzed asymmetric hydrolysis and alcoholysis of vinyl ethers gave valuable axially-chiral 1,1'-bi-2-naphthol and 1,1'-bi-2-phenol derivatives and chiral P-chirogenic compounds in optically active form. The reaction is applied for hydrolytic deallylation of N-allyl amide and allyl esters. The later one was achieved by palladium/ruthenium dual catalysts which is the first example of catalytic irreversible ester hydrolysis. Gold complexes also catalyzed vinyl ether alcoholysis and hydroalkoxylation of olefins. In the later reaction, simple unactivated olefins can be used as substrates and gave the product in 92% yield. The copper-DTBM-SEGPHOS complex catalyzed alcoholysis of azlactones which is the first example showing zero-order kinetic resolution..
63. Lifen Yang, Shozo Kinoshita, Teppei Yamada, Seiichi Kanda, Hiroshi Kitagawa, Makoto Tokunaga, Takayoshi Ishimoto, Teppei Ogura, Ryo Nagumo, Akira Miyamoto, Michihisa Koyama, A Metal-Organic Framework as an Electrocatalyst for Ethanol Oxidation, Angewandte Chemie - International Edition, 10.1002/anie.201000863, 2010.07, (Figer Presented)No need for nobles: The copper-based metal-organic framework material N,N′-bis(2-hydroxyethyl)dithiooxamidatocopper(II) (see picture, Cu pink, N blue, S yellow, O red, C gray, H white) is an active catalyst for ethanol electrooxidation. The performance of this noble-metalfree material is comparable to those of some reported Pt-based catalysts..
64. Xiaohao Liu, Makoto Tokunaga, Controllable Fischer-Tropsch Synthesis by InSitu-Produced 1-Olefins, ChemCatChem, 10.1002/cctc.201000193, 2010.12.
65. Akiyuki Hamasaki, Eiji Yamamoto, Hisashi Itoh, Makoto Tokunaga, Highly atom efficient catalytic reactions utilizing water and alcohols as reagents, Journal of Organometallic Chemistry, 10.1016/j.jorganchem.2010.08.053, 2011.01, In this accounts, we describe our recent studies on hydrolysis, alcoholysis, and addition of alcohols to organic molecules. The reactions utilizing water and alcohols as a reagent are one of the most basic and simple reactions. The palladium-catalyzed asymmetric hydrolysis and alcoholysis of vinyl ethers gave valuable axially chiral 1,1′-bi-2-naphthol and 1,1′-bi-2-phenol derivatives and chiral P-chirogenic compounds in optically active form. The reaction is applied for hydrolytic deallylation of N-allyl amide and allyl esters. The later one was achieved by palladium/ruthenium dual catalysts which is the first example of catalytic irreversible ester hydrolysis. Gold complexes also catalyzed vinyl ether alcoholysis and hydroalkoxylation of olefins. In the later reaction, simple unactivated olefins can be used as substrates and gave the product in 92% yield. The copper-DTBM-SEGPHOS complex catalyzed alcoholysis of azlactones which is the first example showing zero-order kinetic resolution..
66. Asami Nakamura, Akiyuki Hamasaki, Sachihiko Goto, Masaru Utsunomiya, Makoto Tokunaga, Irreversible catalytic ester hydrolysis of allyl esters to give acids and aldehydes by homogeneous ruthenium and ruthenium/palladium dual catalyst systems, Advanced Synthesis and Catalysis, 10.1002/adsc.201000369, 2011.04, An irreversible hydrolysis reaction of allyl esters (1) into carboxylic acids (2) and propanal (3) was achieved with a ruthenium/palladium (Ru/Pd) dual catalyst system. The optimized catalysts consists of a 1:1:1 mixture of (cyclopentadienyl)tris(acetonitrile)ruthenium hexafluorophosphate {[RuCp(MeCN)3] PF6}, bis(acetonitrile)palladium dichloride [PdCl2(MeCN)2] and 1,6-bis(diphenylphosphanyl)hexane (DPPHex). The reaction proceeds via isomerization of allyl esters to 1-propenyl esters and hydrolysis of them to give 2 and 3. The first isomerization step was virtually catalyzed by the Ru components and the second hydrolysis step was mainly catalyzed by the Pd components. The optimized bidentate phosphine (DPPHex) which has long alkylene chain effectively generates two vacant sites on the Ru centers by bridging coordination. When a chelating bidentate phosphine such as DPPE was employed, only one vacant site remained on the Ru center and resulted in a low activity. This chelating Ru complex of DPPE formed even in the presence of 2 equivalents of Ru or additional 1 equivalent of Pd. These differences in coordination behaviour between DPPHex and 1,2- bis(diphenylphosphanyl)ethane (DPPE) cause the differences of the catalytic activity in the first step. The phosphine coordination to Pd center slightly decreases the activity of second hydrolysis step but which was compensated by the increasing of the stability of Pd. On the whole, the optimized Ru/Pd dual catalyst system exhibited good performances on the irreversible hydrolysis of allyl esters..
67. Eiji Yamamoto, Ayano Nagai, Akiyuki Hamasaki, Makoto Tokunaga, Catalytic asymmetric hydrolysis
Asymmetric hydrolytic protonation of enol esters catalyzed by phase-transfer catalysts
, Chemistry - A European Journal, 10.1002/chem.201100833, 2011.06, Like an enzyme: Asymmetric hydrolysis of enol esters is accomplished by chiral phase-transfer catalysts under biphasic base hydrolysis conditions. Stoichiometric reactions support the generation of a well-organized chiral ammonium hydroxide species (Q+OH-)..
68. Xiaohao Liu, Akiyuki Hamasaki, Tetsuo Honma, Makoto Tokunaga, Anti-ASF distribution in Fischer-Tropsch synthesis over unsupported cobalt catalysts in a batch slurry phase reactor, Catalysis Today, 10.1016/j.cattod.2011.03.030, 2011.10, Fischer-Tropsch synthesis (FTS) over unsupported coprecipitated cobalt catalysts in n-decane in a batch slurry phase reactor by adding water vapor (H2O/CO=0.12 in molar ratio) prior to reaction has been studied. The addition of water vapor exhibits a marked effect on the product selectivity. In the absence of water, the carbon number distribution of FT products follows the classical Anderson-Schulz-Flory (ASF) pattern resulting in a low selectivity (32%) in the desired C10+ hydrocarbons. In contrast, with the promotion of water vapor, the formation of heavy products is appreciably increased up to 87.3% in C10+ hydrocarbons so that the selectivity in the range of C8-C30 increases obviously along with an increase in carbon number (n), which leads to a substantial deviation from ASF pattern. The effect of water is explained by suppressing secondary hydrogenation of 1-olefins and facilitating their readsorption and chain growth..
69. Akiyuki Hamasaki, Akiko Muto, Shingo Haraguchi, Xiaohao Liu, Takanori Sakakibara, Takushi Yokoyama, Makoto Tokunaga, Cobalt oxide supported gold nanoparticles as a stable and readily-prepared precursor for the in situ generation of cobalt carbonyl like species, Tetrahedron Letters, 10.1016/j.tetlet.2011.09.067, 2011.12, A treatment of cobalt oxide supported gold nanoparticles (Au/Co 3O4) under syngas atmosphere effectively generated a cobalt carbonyl-like active species in the reaction vessel. The preparation of Au/Co3O4 was quite simple and the in situ generated cobalt species could be used as a stable and easy handling alternative for dicobalt octacarbonyl without bothersome purification prior to use. The reactions, which are sensitive to the purity of the dicobalt octacarbonyl, such as the alkoxycarbonylation of epoxides and the Pauson-Khand reaction, smoothly progressed with Au/Co3O4..
70. Akiyuki Hamasaki, Hideyuki Kuwada, Makoto Tokunaga, Tert-Butylnitrite as a convenient and easy-removable oxidant for the conversion of benzylic alcohols to ketones and aldehydes, Tetrahedron Letters, 10.1016/j.tetlet.2011.12.006, 2012.02, The oxidation of primary and secondary benzylic alcohols was achieved by using tert-butyl nitrite (t-BuONO) as a stoichiometric oxidant. Various substrates were effectively converted into the corresponding ketones or aldehydes in good to excellent yields. The reaction presumably proceeded by a nitrosyl exchange and a subsequent thermal decomposition of benzylic nitrites. This process would realize an oxidation of alcohols with oxygen in theory by combining with a reproduction of alkyl nitrites from NO and alcohols under an O 2 atmosphere. In addition, almost pure oxidized products were readily obtained by simple evaporation of the reaction mixtures since t-BuONO produced only volatile side products..
71. Tamao Ishida, Hiroto Watanabe, Takashi Takei, Akiyuki Hamasaki, Makoto Tokunaga, Masatake Haruta, Metal oxide-catalyzed ammoxidation of alcohols to nitriles and promotion effect of gold nanoparticles for one-pot amide synthesis, Applied Catalysis A: General, 10.1016/j.apcata.2012.03.006, 2012.05, Transition metal oxides (MnO 2, Co 3O 4, and NiO) are catalytically active for the ammoxidation of alcohols to nitriles. In particular, MnO 2 exhibited remarkably high catalytic activity and selectivity for the ammoxidation of alcohols to produce nitriles. Benzyl alcohol could also be directly converted to benzonitrile by MnO 2 catalyst by the one-pot ammoxidation and the hydration with water which was formed by the first ammoxidation step. The deposition of gold nanoparticles (Au NPs) onto MnO 2 did not enhance the ammoxidation of benzyl alcohol but promoted the hydration of benzonitrile to produce benzamide with high selectivity. In contrast, Au NPs supported on Al 2O 3, CuO, and CeO 2 catalyzed the ammoxidation of benzyl alcohol, whereas these metal oxides themselves were inactive for the ammoxidation or showed low catalytic activity. These results have demonstrated that gold is intrinsically active as a catalyst for the ammoxidation of alcohols..
72. Akiyuki Hamasaki, Shuhei Maruta, Aki Nakamura, Makoto Tokunaga, Palladium-catalyzed 1,4-addition of carboxylic acids to butadiene monoxide, Advanced Synthesis and Catalysis, 10.1002/adsc.201200059, 2012.08, Palladium complexes catalyze the 1,4-addition of acetic acid to butadiene monoxide to give 4-hydroxybut-2-en-1-yl acetate. The highest 1,4-/1,2-addition selectivity of 18.9 was achieved. The reaction seems to proceed via a Wacker-like mechanism..
73. Eiji Yamamoto, Daichi Gokuden, Ayano Nagai, Takashi Kamachi, Kazunari Yoshizawa, Akiyuki Hamasaki, Tamao Ishida, Makoto Tokunaga, Hydrolytic enantioselective protonation of cyclic dienyl esters and a β-diketone with chiral phase-transfer catalysts, Organic Letters, 10.1021/ol3027363, 2012.12, Hydrolytic enantioselective protonation of dienyl esters and a β-diketone catalyzed by phase-transfer catalysts are described. The latter reaction is the first example of an enantio-convergent retro-Claisen condensation. Corresponding various optically active α,β-unsaturated ketones having tertiary chiral centers adjacent to carbonyl groups were obtained in good to excellent yields and enantiomeric ratios (83-99%, up to 97.5:2.5 er)..
74. Tamao Ishida, Tatsuya Yanagihara, Xiaohao Liu, Hironori Ohashi, Akiyuki Hamasaki, Tetsuo Honma, Hiroshi Oji, Takushi Yokoyama, Makoto Tokunaga, Synthesis of higher alcohols by Fischer-Tropsch synthesis over alkali metal-modified cobalt catalysts, Applied Catalysis A: General, 10.1016/j.apcata.2013.03.042, 2013.05, Alkali metal-modified unsupported and supported cobalt catalysts worked efficiently in the Fischer-Tropsch (FT) synthesis for the production of higher alcohols in a batch slurry-phase reactor. Sodium-modified Co catalysts exhibited the highest catalytic performance in terms of catalytic activity and higher alcohol selectivities compared to other alkali metal-modified Co catalysts: they also gave appreciable amounts of higher alcohols with more than four carbon atoms (C5+ alcohols) as much as 77% of the total alcohol distribution. According to the characterization of the catalysts using XRD, TEM, XPS, XAFS, and CO2-TPD, the effect of Na was suggested as follows: (i) a decrease in the size of Co nanoparticles, (ii) a decrease in the reducibility of Co(II) to Co(0), and (iii) an increase in surface basicity. These factors enable the production of higher alcohols with high selectivities at high CO conversions..
75. Takayoshi Ishimoto, Teppei Ogura, Michihisa Koyama, Lifen Yang, Shozo Kinoshita, Teppei Yamada, Makoto Tokunaga, Hiroshi Kitagawa, A key mechanism of ethanol electrooxidation reaction in a noble-metal-free metal-organic framework, Journal of Physical Chemistry C, 10.1021/jp4031046, 2013.05, We elucidated theoretically an electrooxidation reaction mechanism of ethanol on a metal-organic framework (MOF) electrocatalyst, (HOC 2H4)2dtoaCu (H2dtoa = dithiooxamide), by using the density functional theory method. The indirect proton transfer from ethanol to the MOF via the HOC2H4 group is revealed to be a key mechanism controlling the reactivity of ethanol oxidation on MOF. We have also studied the ethanol oxidation reaction pathways on a series of R2dtoaCu (R = HOC3H6, C 2H5, C3H7, CH3, and H). Three dominant factors in the electrooxidation activity of R2dtoaCu were identified: (1) adsorptive interaction with the MOF; (2) strain in the backbone structure that enhances its activity as a proton acceptor; and (3) a proton-transfer pathway from ethanol to R2dtoaCu. These theoretical identifications are confirmed with the experimental results for ethanol sorption isotherms and the activity of the ethanol electrooxidation reaction measured for R2dtoaCu (R = HOC3H6 and C 2H5). We are the first to demonstrate the oxidation reaction mechanism of the MOF electrocatalyst for ethanol with theoretical study..
76. Akiyuki Hamasaki, Tamao Ishida, Makoto Tokunaga, Novel feature and catalysis of metal oxide supported gold nanoparticles, Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry, 10.5059/yukigoseikyokaishi.71.443, 2013.07, Gold nanoparticles are drawing great attention because of its interesting properties. Although a bulk gold is chemically inert, a nano-sized particles shows completely different characteristics. Therefore, applications of gold nanoparticles for organic transformations are wide-spreading in recent years. We have developed several organic reactions employing metal oxide supported gold nanoparticles. In these reactions, the catalysis are assumed not only by gold nanoparticles but an active species formed from oxide support depending on the reaction conditions. This phenomenon expands the capability of metal oxide supported gold nanoparticles since the catalysis can be modulated by employing a proper metal oxide support..
77. Hiroaki Nishikawa, Daisuke Kawamoto, Yusuke Yamamoto, Tamao Ishida, Hironori Ohashi, Tomoki Akita, Tetsuo Honma, Hiroshi Oji, Yasuhiro Kobayashi, Akiyuki Hamasaki, Takushi Yokoyama, Makoto Tokunaga, Promotional effect of Au on reduction of Ni(II) to form Au-Ni alloy catalysts for hydrogenolysis of benzylic alcohols, Journal of Catalysis, 10.1016/j.jcat.2013.07.027, 2013.09, Gold-nickel bimetallic catalysts were prepared from Au/NiO and Au(OH) 3-Ni(OH)2-NiCO3 coprecipitates by treatment with hydrogen. Gold promoted the reduction of Ni(II) to Ni(0) at relatively low temperatures in the range of 100-150 C, which was confirmed by H2-TPR and in situ XAFS measurements, whereas NiO without Au was not fully reduced even at 300 C. The obtained catalysts were characterized by XRD, HAADF-STEM, XAFS, and 197Au Mössbauer, and these analyses revealed the formation of Au-Ni alloy components in the obtained catalysts. Au existed as Au nanoparticles together with Au-Ni alloy components in Au-Ni-1 prepared from Au/NiO by H2 treatment. When Au(OH)3-Ni(OH) 2-NiCO3 was treated in a flow of H2 to produce Au-Ni-2, the formation of Au NPs was not clearly observed, thereby meaning that Au atoms were highly dispersed as a single atom and/or small clusters in the obtained catalysts. Moreover, most of the Au atoms were alloyed with Ni atoms for Au-Ni-2. The obtained Au-Ni-1 and Au-Ni-2 exhibited superior catalytic activities for the selective hydrogenolysis of benzylic alcohols into alkylbenzene derivatives in terms of reaction rates normalized by catalyst surface area. Accordingly, Au-Ni-1 and Au-Ni-2 recorded the reaction rates of 4.79 and 9.79 mmol L-1 h-1 m-2, respectively. These values were greater than that obtained for Raney Ni (0.14 mmol L -1 h-1 m-2). In addition, Au-Ni-2, which contains higher Au-Ni alloy content, showed greater reaction rates when compared to Au-Ni-1. Since Au/TiO2 showed poor catalytic activity for the hydrogenolysis, Au-Ni alloy enhanced the catalytic activities of Ni(0)..
78. Xiaohao Liu, Akiyuki Hamasaki, Yoshihiro Yamane, Shohei Aikawa, Tamao Ishida, Masatake Haruta, Makoto Tokunaga, Gold nanoparticles assisted formation of cobalt species for intermolecular hydroaminomethylation and intramolecular cyclocarbonylation of olefins, Catalysis Science and Technology, 10.1039/c3cy00336a, 2013.10, The intermolecular hydroaminomethylation and the intramolecular cyclocarbonylation efficiently proceeded on cobalt oxide supported gold nanoparticles. The intermolecular reaction employing terminal olefins and N-isopropylaniline afforded hydroaminomethylated products as a mixture of regioisomers via a common reaction path consisting of hydroformylation, imine formation, and hydrogenation. In contrast, indolinone derivatives were exclusively obtained in the case of 2-alkenylanilines based on the intramolecular cyclocarbonylation mechanism. Both of these reactions were catalyzed by cobalt species derived from cobalt oxide. The active cobalt species were formed via reduction of the oxide support promoted by deposited gold nanoparticles. Characterization of the catalysts before and after the reaction was also performed..
79. Tamao Ishida, Jun Aimoto, Akiyuki Hamasaki, Hironori Ohashi, Tetsuo Honma, Takushi Yokoyama, Kohei Sakata, Mitsutaka Okumura, Makoto Tokunaga, Formation of gold clusters on La-Ni mixed oxides and its catalytic performance for isomerization of allylic alcohols to saturated aldehydes, Chemistry Letters, 10.1246/cl.140369, 2014.01, Au/NiO catalyzed the isomerization of allylic alcohols to afford saturated aldehydes. LaNi mixed oxide could stabilize Au(III) and afford gold clusters smaller than 1 nm by H2reduction. The resulting Au clusters on La-Ni-O exhibited superior catalytic performance to Au/NiO for the isomerization of internal allylic alcohol, 2-octen-1-ol to octanal..
80. Akiyuki Hamasaki, Yutaro Yasutake, Takafumi Norio, Tamao Ishida, Tomoki Akita, Hironori Ohashi, Takushi Yokoyama, Tetsuo Honma, Makoto Tokunaga, Cooperative catalysis of palladium nanoparticles and cobalt oxide support for formylation of aryl iodides under syngas atmosphere, Applied Catalysis A: General, 10.1016/j.apcata.2013.09.043, 2014.01, Formylation of aryl iodides proceeded effectively in the presence of palladium nanoparticles on cobalt oxide under a syngas atmosphere to afford aldehydes up to 91% yield. A cooperative effect between palladium nanoparticles and cobalt species derived from the support was integral to efficient transformation. Both palladium and cobalt were revealed to exist as zero valent metals after H2 treatment from X-ray absorption near edge structure and X-ray diffraction spectra. The catalyst could be reused at least 7 times without significant loss of activity..
81. Tamao Ishida, Ryosuke Tsunoda, Zhenzhong Zhang, Akiyuki Hamasaki, Tetsuo Honma, Hironori Ohashi, Takushi Yokoyama, Makoto Tokunaga, Supported palladium hydroxide-catalyzed intramolecular double CH bond functionalization for synthesis of carbazoles and dibenzofurans, Applied Catalysis B: Environmental, 10.1016/j.apcatb.2013.12.051, 2014.05, Metal oxide-supported palladium hydroxide (Pd(OH)2/MOx) catalysts enabled the oxidative intramolecular couplings of diarylamines to carbazoles and diarylethers to dibenzofurans via double aryl CH bond functionalizations with molecular oxygen as the sole oxidant. While supported PdO, Pd, and palladium acetate catalysts showed poor catalytic activities, supported Pd(OH)2 exhibited remarkably high catalytic activity. Among supported Pd(OH)2 catalysts, Pd(OH)2/ZrO2 was found to be an efficient catalyst in terms of catalytic activities and selectivities for the synthesis of carbazoles and dibenzofurans..
82. Ren Tomita, Kohei Mantani, Akiyuki Hamasaki, Tamao Ishida, Makoto Tokunaga, Homogeneous Pd-catalyzed transformation of terminal alkenes into primary allylic alcohols and derivatives, Chemistry - A European Journal, 10.1002/chem.201403373, 2014.08, Synthesis of primary alcohols from terminal alkenes is an important process in both bulk and fine chemical syntheses. Herein, a homogeneous Pd-complex-catalyzed transformation of terminal alkenes into primary allylic alcohols, by using 5 mol % [Pd(PPh3)4] as a catalyst, and H2O, CO2, and quinone derivatives as reagents, is reported. When alcohols were used instead of H2O, allylic ethers were obtained. A proposed mechanism includes the addition of oxygen nucleophiles at the less-hindered terminal position of π-allyl Pd intermediates..
83. Tamao Ishida, Yuta Onuma, Kota Kinjo, Akiyuki Hamasaki, Hironori Ohashi, Tetsuo Honma, Tomoki Akita, Takushi Yokoyama, Makoto Tokunaga, Masatake Haruta, Preparation of microporous polymer-encapsulated Pd nanoparticles and their catalytic performance for hydrogenation and oxidation, Tetrahedron, 10.1016/j.tet.2014.04.049, 2014.09, Palladium nanoparticles (Pd NPs) encapsulated by conjugated microporous polymers (CMPs) were prepared by the Pd-catalyzed polymerization followed by a thermal treatment with N2 or H2. The Pd catalysts were embedded in the porous network during polymerization and used as a precursor for the generation of Pd NPs in CMP. Although no Pd NPs were formed in the as-synthesized Pd/CMPs, Pd NPs with 1.6-3.5 nm size were formed after the thermal treatment. The obtained Pd/CMP-N2 and -H2 catalysts were highly selective in the hydrogenation of 4-nitrostyrene to 4-ethylnitrobenzene, whereas Pd NPs supported on carbon (Ketjen black) gave a fully reduced product, 4-ethylaniline. Substituents in CMP framework could change the catalytic activity of Pd NPs; hydroxy-substituted CMP encapsulated Pd NPs showed higher catalytic activity than Pd/CMP-H2 for benzyl alcohol oxidation..
84. Tamao Ishida, Shohei Aikawa, Yoshiyuki Mise, Ryota Akebi, Akiyuki Hamasaki, Tetsuo Honma, Hironori Ohashi, Tetsuro Tsuji, Yasushi Yamamoto, Mitsuru Miyasaka, Takushi Yokoyama, Makoto Tokunaga, Direct C - H arene homocoupling over gold nanoparticles supported on metal oxides, ChemSusChem, 10.1002/cssc.201402822, 2015, The direct C - H/C - H bond coupling of dimethyl phthalate was performed successfully over supported gold nanoparticle catalysts. Gold on reducible metal oxides, such as Co3O4, and on inert oxides that have an oxygen-releasing capacity, such as ZrO2, showed the highest catalytic activity for the production of biphenyl tetracarboxylate using O2 as the sole oxidant. Supported Pd(OH)2 also catalyzed the reaction, but the catalytic activity was inferior to that of gold. Moreover, the gold catalysts exhibited excellent regioselectivity for the synthesis of valuable 3,3′,4,4′-tetrasubstituted biphenyls by coupling with each other at the 4-position without the need for additional ligands. Gold catalysts also promoted the oxidative homocoupling of arenes including o-xylene to give symmetrical biaryls with high regioselectivity. X-ray absorption fine structure measurements revealed that the catalytically active species was Au0 and that the lattice oxygen of Co3O4 played an important role in the gold-catalyzed oxidative coupling. The results of the kinetic studies were consistent with an electrophilic aromatic substitution pathway. Regioselectivity is not controlled by directing groups or the electronic character of the substituents but by steric hindrance, which suggests that gold nanoparticles not only catalyze the oxidative coupling but also act as bulky ligands to control the regioselectivity..
85. Zhenzhong Zhang, Taishin Hashiguchi, Tamao Ishida, Akiyuki Hamasaki, Tetsuo Honma, Hironori Ohashi, Takushi Yokoyama, Makoto Tokunaga, Aerobic oxidation of cyclohexanones to phenols and aryl ethers over supported Pd catalysts, Organic Chemistry Frontiers, 10.1039/c4qo00354c, 2015.01, Transformation of cyclohexanones to phenols and aryl ethers over supported Pd catalysts using molecular oxygen as the sole oxidant is developed. Several metal oxide supported Pd catalysts were used to activate the C-H bond in cyclohexanones to produce cyclohexenones and phenols through oxidation. Although the selectivity of cyclohexenones was difficult to control, phenols were obtained in excellent yield with a broad substrate scope. A novel catalytic system, using ZrO2 supported Pd(OH)2, was proposed for the synthesis of aryl ethers, and the products were obtained in moderate to excellent yields. Orthoesters, such as trimethyl orthoformate (TMOF), triethyl orthoformate (TEOF), and triisopropyl orthoformate (TIPOF), enabled nucleophilic addition and elimination after activation of cyclohexanones over a Pd catalyst to produce the corresponding aryl ethers. TIPOF was also used as the dehydrating reagent to promote the reaction of cyclohexanones with alcohols for the preparation of versatile aryl ethers..
86. K. Sakata, H. Koga, T. Ishida, J. Aimoto, Makoto Tokunaga, M. Okumura, Theoretical investigation for isomerization of allylic alcohols over Au6 cluster, Gold Bulletin, 10.1007/s13404-015-0157-1, 2015.08, Transformation of allylic alcohols to corresponding saturated carbonyl compounds is one of the important reactions for industrial processes. Lately, Au-supported catalysts exhibit the catalytic activity for the isomerization of allylic alcohols to saturated aldehydes. However, the detail catalytic mechanism of this reaction was not elucidated in detail. Thus, theoretical calculations were carried out for the isomerization of 2-hexen-1-ol over isolated Au6 cluster in order to elucidate the reaction over Au catalysts. From these calculation results, it was found that the rate determining step of the reaction process was the hydrogen elimination from OH group of allylic alcohol, and the substrate was converted to 1-hexen-1-ol on Au6 cluster. Finally, it was also confirmed that 1-hexen-1-ol was converted to the corresponding aldehyde, and its activation barrier was much smaller than that of the deprotonation from OH group of allylic alcohol..
87. Daisuke Kawamoto, Hiroaki Ando, Hironori Ohashi, Yasuhiro Kobayashi, Tetsuo Honma, Tamao Ishida, Makoto Tokunaga, Yoshihiro Okaue, Satoshi Utsunomiya, Takushi Yokoyama, Structure of a gold(III) hydroxide and determination of its solubility, Bulletin of the Chemical Society of Japan, 10.1246/bcsj.20160228, 2016, A representative gold(III) complex ion ([AuCl4]), successively hydrolyzes to form [AuCl4n(OH)n] (n = 04) in aqueous solution as the pH increases and, finally, precipitates. It has been referred to as gold(III) hydroxide for the past fifty years. However, whether the precipitate is gold(III) hydroxide (Au(OH)3) or hydrous gold(III) oxide (Au2O3nH2O) has remained uncertain. Few studies have been conducted to determine its chemical and physical properties. The aim of this investigation is to identify the precipitate and to determine its solubility. The precipitate was X-ray amorphous. Based on the transmission electron microscopy (TEM) observation, the shape was spherical and the particle diameter was approximately 9 nm. From the results of 197Au Mössbauer spectroscopy, Au L3-edge X-ray absorption (XA) spectroscopy and thermogravimetry/ differential thermal analysis (TG/DTA) measurements, the precipitate composition was estimated to be Au(OH)3. Based on the composition, its structure was proposed to be a linear polymer. Moreover, its solubility at 298K was determined to be 0.00120 g/100 g of H2O. This chemical and physical properties information of Au(OH)3 is essential for gold chemistry, for example, for preparing supported gold catalyst..
88. Structure of a Gold(III) Hydroxide and Determination of Its Solubility.
89. Tamao Ishida, Kurumi Kume, Kota Kinjo, Tetsuo Honma, Kengo Nakada, Hironori Ohashi, Takushi Yokoyama, Akiyuki Hamasaki, Haruno Murayama, Yusuke Izawa, Masaru Utsunomiya, Makoto Tokunaga, Efficient Decarbonylation of Furfural to Furan Catalyzed by Zirconia-Supported Palladium Clusters with Low Atomicity, ChemSusChem, 10.1002/cssc.201601232, 2016.01, Decarbonylation of furfural to furan was efficiently catalyzed by ZrO2-supported Pd clusters in the liquid phase under a N2atmosphere without additives. Although Pd/C and Pd/Al2O3have frequently been used for decarbonylation, Pd/ZrO2exhibited superior catalytic performance compared with these conventional catalysts. Transmission electron microscopy and X-ray absorption fine structure measurements revealed that the size of the Pd particles decreased with an increase in the specific surface area of ZrO2. ZrO2with a high surface area immobilized Pd as clusters consisting of several (three to five) Pd atoms, whereas Pd aggregated to form nanoparticles on other supports such as carbon and Al2O3despite their high surface areas. The catalytic activity of Pd/ZrO2was enhanced with a decrease in particle size, and the smallest Pd/ZrO2was the most active catalyst for decarbonylation. When CeO2was used as the support, a decrease in Pd particle size with an increase in surface area was also observed. Single Pd atoms were deposited on CeO2with a high surface area, with a strong interaction through the formation of a Pd−O−Ce bond, which led to a lower catalytic activity than that of Pd/ZrO2. This result suggests that zero-valent small Pd clusters consisting of more than one Pd atom are the active species for the decarbonylation reaction. Recycling tests proved that Pd/ZrO2maintained its catalytic activity until its sixth use..
90. Mamiko Yamashita Maeno, Hironori Ohashi, Kotaro Yonezu, Akane Miyazaki, Yoshihiro Okaue, Koichiro Watanabe, Tamao Ishida, Makoto Tokunaga, Takushi Yokoyama, Sorption behavior of the Pt(II) complex anion on manganese dioxide (δ-MnO2)
a model reaction to elucidate the mechanism by which Pt is concentrated into a marine ferromanganese crust
, Mineralium Deposita, 10.1007/s00126-015-0599-7, 2016.02, It is difficult to directly investigate the chemical state of Pt in marine ferromanganese crusts (a mixture of hydrous iron(III) oxide and manganese dioxide (δ-MnO2)) because it is present at extremely low concentration levels. This paper attempts to elucidate the mechanism by which Pt is concentrated into marine ferromanganese crust from the Earth’s continental crust through ocean water. In this investigation, the sorption behavior of the Pt(II) complex ions on the surface of the δ-MnO2 that is a host of Pt was examined as a model reaction. The δ-MnO2 sorbing Pt was characterized by X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) to determine the chemical state of the Pt. Hydrolytic Pt(II) complex ions were specifically sorbed above pH 6 by the formation of a Mn-O-Pt bond. XPS spectra and XANES spectra for δ-MnO2 sorbing Pt showed that the sorbed Pt(II) was oxidized to Pt(IV) on δ-MnO2. The extended X-ray absorption fine structure (EXAFS) analysis showed that the coordination structure of Pt sorbed on δ-MnO2 is almost the same as that of the [Pt(OH)6]2− complex ion used as a standard. Therefore, the mechanism for the concentration of Pt in marine ferromanganese crust may be an oxidative substitution (penetration of Pt(IV) into structure of δ-MnO2) by a reduction-oxidation reaction between Pt(II) in [PtCl4-n(OH)n]2− and Mn(IV) in δ-MnO2 through a Mn-O-Pt bond..
91. Zhenzhong Zhang, Qixun Wu, Taishin Hashiguchi, Tamao Ishida, Haruno Murayama, Makoto Tokunaga, Allylic C–H acetoxylation of terminal alkenes over TiO2 supported palladium nanoparticles using molecular oxygen as the oxidant, Catalysis Communications, 10.1016/j.catcom.2016.08.033, 2016.12, A method for synthesizing linear allylic acetates from terminal alkenes over TiO2 supported Pd nanoparticles (NPs) has been developed, in which O2 serves as the sole oxidant. Good catalytic activity was performed when using allylbenzene as a substrate and the catalyst can be reused at least five times without activity losing. The catalytic system has a broad substrate scope including transformation of 1,3-butadiene into 1,4-diacetoxy-2-butene, which is an important industrial intermediate for production of 1,4-butanediol. In contrast to previous reports that the Pd-catalyzed allylic acetoxylation is generally promoted by PdII species, the XAFS measurements suggest that this reaction is catalyzed over Pd0 NPs. Additionally, XPS analysis of the catalyst confirms the interaction between Pd and TiO2, which probably promote the initial catalytic procedure..
92. Zhenzhong Zhang, Yuhya Kumamoto, Taishin Hashiguchi, Tetsuya Mamba, Haruno Murayama, Eiji Yamamoto, Tamao Ishida, Tetsuo Honma, Makoto Tokunaga, Wacker Oxidation of Terminal Alkenes Over ZrO2-Supported Pd Nanoparticles Under Acid- and Cocatalyst-Free Conditions, ChemSusChem, 10.1002/cssc.201701016, 2017.01, Highly efficient Wacker oxidation of aromatic or aliphatic terminal alkenes into methyl ketones and benzofurans is developed by using reusable Pd0 nanoparticles (NPs) supported on ZrO2 under acid- and cocatalyst-free conditions. Molecular oxygen or air can be utilized as the terminal oxidant, which results in the formation of H2O as the only theoretical byproduct. The activation of the Pd NPs by O2 plays an important role in promoting this reaction. Interestingly, PdO supported on ZrO2 showed no activity. Additionally, the Pd particle size significantly affects the catalytic activity, with an apparent optimal diameter of 4–12 nm. In addition to the heterogeneous catalyst forms, the Pd NPs can be generated from a Pd0 complex during the reaction, and these particles are even recyclable..
93. Tamao Ishida, Zhenzhong Zhang, Haruno Murayama, Makoto Tokunaga, Oxide-supported palladium and gold nanoparticles for catalytic C-H transformations, Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry, 10.5059/yukigoseikyokaishi.75.1150, 2017.01, C-H transformations catalyzed by heterogeneous Pd and Au catalysts are disclosed. For palladium, Pd(0), PdO, and Pd(OH) 2 worked as catalytically active species involved in oxidative addition, electrophilic substitution, and concerted metalation deprotonation pathways depending on the reaction under investigation. We also found that Au(0) nanoparticles catalyzed C-H coupling and discuss the difference in catalytic properties between Pd and Au. The role of metal oxide (MO x) supports is also mentioned: MO x not only stabilizes Pd and Au particles but also creates cationic metal sites at the perimeter interface, and these play an important role in activating the substrates..
94. Haruno Murayama, Takayuki Hasegawa, Yusuke Yamamoto, Misaki Tone, Moemi Kimura, Tamao Ishida, Tetsuo Honma, Mitsutaka Okumura, Atsuko Isogai, Tsutomu Fujii, Makoto Tokunaga, Chloride-free and water-soluble Au complex for preparation of supported small nanoparticles by impregnation method, Journal of Catalysis, 10.1016/j.jcat.2017.07.002, 2017.01, A novel simple and easy impregnation method for preparation of small gold (Au) nanoparticle (NP) catalysts (<3 nm) deposited on various supports including silica, which is difficult to be applied for conventional methods, has been developed. Chloride-free and water-soluble precursor, Au complexes coordinated with β-alanine, were successful for the preparing Au NPs, which exhibited an average diameter less than 3 nm. Thermal behavior of the Au complex was investigated by TG-DTA and in situ XAFS. XAFS analyses and DFT calculations revealed a molecular structure of the Au complex to be square-planar coordination structure and mononuclear complex of Au3+. Lower decomposition and reduction temperature of the chloride-free Au complex prevented Au atoms from aggregating and from following growth of Au particles. The prepared Au/SiO2 showed high selectivity for hydrogenation of 1-nitro-4-vinylbenzene into 1-ethyl-4-nitorobenzene and good performance for removal of unpalatable aroma by means of adsorption of polysulfide molecules..
95. Hiroaki Ando, Daisuke Kawamoto, Hironori Ohashi, Tetsuo Honma, Tamao Ishida, Yoshihiro Okaue, Makoto Tokunaga, Takushi Yokoyama, Adsorption Behavior of Au(III) Complex Ion on Nickel Carbonate and Nickel Hydroxide, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 10.1016/j.colsurfa.2017.10.028, 2018.01, When preparing gold(Au) supported on NiO catalysts by the coprecipitation method, the chemical state of the coprecipitated Au differed when Na2CO3 and NaOH were used as the coprecipitating reagents. In this preparation using Na2CO3 and NaOH solutions, precursor of support metal was largely NiCO3 and Ni(OH)2, respectively. Therefore, the different chemical states of Au may be controlled by the interaction between the [Au(OH)4] and precursor of support metal. The aim of this study is to elucidate why the chemical state of Au differs when using NiCO3 and Ni(OH)2. Adsorption experiments of [Au(OH)4] onto NiCO3 or Ni(OH)2 were performed. The Au concentration in the filtrate was determined by atomic absorption spectrometry (AAS). The chemical state of the adsorbed Au was examined by X-ray absorption(XA) spectroscopy. The adsorption experiments suggested that the change in surface charge on NiCO3 and Ni(OH)2 electrostatically controls the adsorption of [Au(OH)4]. The XA analysis indicated that the chemical state of [Au(OH)4] adsorbed on NiCO3 is maintained because of electrostatic interactions, while some of the [Au(OH)4] adsorbed on Ni(OH)2 may be reduced to Au(0) due to specific adsorption-accompanying distortion of the square planar structure of the adsorbed [Au(OH)4]..
96. Tokunaga, M.; Aoyama, H.; Obora, Y.; Tsuji, T., Catalytic hydrolysis and alcoholysis of alkenyl esters and ethers and its application to kinetic resolution., Transworld Research Network, Kerala, India., 2005, 9, 147-160., 2005.12.