Faculty Profiles - SUGA Seiji

Papers - SUGA Seiji

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Electro-initiated coupling reactions of N-acyliminium ion pools with arylthiomethylsilanes and aryloxymethylsilanes

Seiji Suga, Ikuo Shimizu, Yosuke Ashikari, Yusuke Mizuno, Tomokazu Maruyama, Jun ichi Yoshida

Chemistry Letters 37 ( 9 ) 1008 - 1009 2008.9

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

Electro-initiated coupling reactions of N-acyliminium ion with arylthiomethylsilanes and aryloxymethylsilanes were developed. Pulse electrolyses with intervals were found to be quite effective for the initiation. A chain mechanism involving cation, radical cation, and radical intermediates has been proposed. Copyright © 2008 The Chemical Society of Japan.

DOI： 10.1246/cl.2008.1008

Microflow system controlled carbocationic polymerization of vinyl ethers

Aiichiro Nagaki, Takeshi Iwasaki, Kohsuke Kawamura, Daisuke Yamada, Seiji Suga, Tuyoshi Ando, Mitsuo Sawamoto, Jun Ichi Yoshida

Chemistry - An Asian Journal 3 ( 8-9 ) 1558 - 1567 2008.9

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

A "cation pool" of an Nacyliminium ion was found to serve as an effective initiator of cationic polymerization of vinyl ethers in a microflow system consisting of two micromixers (IMM micromixer) and two microtube reactors. The cationic polymerization of n-butyl vinyl ether in CH 2Cl2 at -78°C led to very narrow molecular weight distribution (Mw/Mn=1.14). The molecular weight (M n) increased linearly with an increase in monomer/initiator ratio. The carbocationic polymer end was effectively trapped by allyltrimethylsilane. Additionally, the synthesis of block polymers was accomplished by the present microflow system controlled method. The polymerization was also conducted using commercially available trifluoromethanesulfonic acid (TfOH) as an initiator. A high level of molecular weight control was attained even at -25°C. The TfOH-initiated polymerization could be conducted using a microflow system based on T-shaped micromixers, which serves as a practical tool for microflow system controlled carbocationic polymerization. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.

DOI： 10.1002/asia.200800081

Iterative molecular assembly based on the cation-pool method. Convergent synthesis of dendritic molecules

Toshiki Nokami, Kousuke Ohata, Masafumi Inoue, Hiroaki Tsuyama, Akito Shibuya, Kazuya Soga, Masayuki Okajima, Seiji Suga, Jun Ichi Yoshida

Journal of the American Chemical Society 130 ( 33 ) 10864 - 10865 2008.8

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

An iterative method for molecular assembly has been developed based on the cation-pool method using (trimethylsilyl)diphenylmethane as a building block. The silyl group works as both an activating group of the benzene ring in the Friedel-Crafts type reaction and an electroauxiliary in the subsequent low temperature anodic oxidation to generate dendritic diarylcarbenium ions, which were well characterized by low-temperature NMR spectroscopy. The convergent synthesis of dendritic molecules has been achieved by repeating the sequence. Copyright © 2008 American Chemical Society.

DOI： 10.1021/ja803487q

An electroinitiated cation chain reaction: Intramolecular carbon-carbon bond formation between thioacetal and olefin groups

Kouichi Matsumoto, Shunsuke Fujie, Koji Ueoka, Seiji Suga, Jun Ichi Yoshida

Angewandte Chemie - International Edition 47 ( 13 ) 2506 - 2508 2008.3

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

(Figure Presented) The treatment of an olefinic thioacetal with a catalytic amount of ArS(ArSSAr)-+B(C6F5) 4-, or the electrolysis of a mixture of an olefinic thioacetal and ArSSAr, gives rise to effective intramolecular carbon-carbon bond formation (see scheme). This transformation opens up great potential for electroinitiated cation chain reactions in organic synthesis. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.

DOI： 10.1002/anie.200705748

Electrochemical generation of glycosyl triflate pools

Toshiki Nokami, Akito Shibuya, Hiroaki Tsuyama, Seiji Suga, Albert A. Bowers, David Crich, Jun Ichi Yoshida

Journal of the American Chemical Society 129 ( 35 ) 10922 - 10928 2007.9

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Glycosyl triflates, which serve as important intermediates in glycosylation reactions, were generated and accumulated by the low-temperature electrochemical oxidation of thioglycosides such as thioglucosides, thiogalactosides, and thiomannosides in the presence of tetrabutylammonium triflate (Bu4-NOTf) as a supporting electrolyte. Thus-obtained solutions of glycosyl triflates (glycosyl triflate pools) were characterized by low-temperature NMR measurements. The thermal stability of glycosyl triflates and their reactions with glycosyl acceptors were also examined. © 2007 American Chemical Society.

DOI： 10.1021/ja072440x

Reactions of a N-acyliminium ion pool with benzylsilanes. Implication of a radical/cation/radical cation chain mechanism involving oxidative C-Si bond cleavage

Tomokazu Maruyama, Yusuke Mizuno, Ikuo Shimizu, Seiji Suga, Jun Ichi Yoshida

Journal of the American Chemical Society 129 ( 7 ) 1902 - 1903 2007.2

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

The reaction of a N-acyliminium ion pool with benzylsilane proceeds by a chain mechanism involving oxidative C-Si bond cleavage. A radical/cation/radical cation crossover mechanism involving single electron transfer has been proposed. The effective binary system consisting of a stoichiometric amount of a benzylsilane and a catalytic amount of a more easily oxidized benzylstannane has been developed. Copyright © 2007 American Chemical Society.

DOI： 10.1021/ja068589a

Oxidative generation of diarylcarbenium ion pools

Masayuki Okajima, Kazuya Soga, Toshiki Nokami, Seiji Suga, Jun Ichi Yoshida

Organic Letters 8 ( 22 ) 5005 - 5007 2006.10

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

(Figure Presented) "Cation pools" of diarylcarbenium ions have been generated by the oxidative C-H bond dissociation of diarylmethanes using anodic oxidation. "Diarylcarbenium ion pools" thus generated react with various nucleophiles, such as allylsilanes, ketene silyl acetals, and aromatic compounds. The reductive homocoupling of the "diarylcarbenium ion pool" has been achieved. The dimer thus obtained also serves as a precursor of the "diarylcarbenium ion pool" via oxidative C-C bond dissociation. © 2006 American Chemical Society.

DOI： 10.1021/ol061647c

Organic synthesis using carbocations generated by electron transfer reactions

Seiji Suga

Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry 64 ( 10 ) 1010 - 1020 2006.10

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：SOC SYNTHETIC ORGANIC CHEM JPN

We have developed the "cation pool" method in which carbocations such as alkoxycarbenium ions and N-acyliminium ions are generated and accumulated in conventional reaction media by low temperature electrochemical oxidation. The carbocations thus produced are allowed to react with a variety of nucleophiles. Various organic transformations using the cation pool method, such as reductive radical couplings, cationic carbohydroxylations, three-component couplings, and additions of organic radicals, have also been developed. Combinatorial sequential synthesis using the "cation flow" method, in which carbocations are generated in an electrochemical microflow system, has been achieved as well.

DOI： 10.5059/yukigoseikyokaishi.64.1010

Electroauxiliary-assisted sequential introduction of organic groups on the α-carbons of nitrogen

Seiji Suga, Mitsuru Watanabe, Chun Hong Song, Jun Ichi Yoshida

Electrochemistry 74 ( 8 ) 672 - 679 2006.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ELECTROCHEMICAL SOC JAPAN

A method for sequential introduction of two organic groups on the same or the different α-carbons of nitrogen has been developed based on a combination of the concept of electroauxiliary and the cation pool method. Selective introduction of two carbon nucleophiles into 2,5- or 2,2-position of pyrrolidine has been accomplished via sequential electrochemical oxidation of pyrrolidine derivatives containing two silyl groups as the electroauxiliaries. Introduction of two carbon nucleophiles into 2,6-position of piperidine was also successful. The products having two olefinic groups were effectively converted to nitrogen-containing spiro compounds using ring closing metathesis, and an application to formal synthesis of cephalotaxine was also carried out. These results clearly illustrate the synthetic utility and potential of the present approach, and open a new aspect of the synthesis of nitrogen-containing compounds.

DOI： 10.5796/electrochemistry.74.672

Distannane mediated reaction of N-acyliminium ion pools with alkyl halides. A chain mechanism involving radical addition followed by electron transfer

Tomokazu Maruyama, Seiji Suga, Jun ichi Yoshida

Tetrahedron 62 ( 27 ) 6519 - 6525 2006.7

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

Hexabutyldistannane was found to be an effective mediator allowing the reaction of N-acyliminium ion pools with alkyl halides. A chain mechanism involving the addition of an alkyl radical generated from an alkyl halide to an N-acyliminium ion followed by the one-electron reduction of the resulting radical-cation by distannane was proposed. © 2006 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tet.2006.03.114

Indirect cation pool method. Rapid generation of alkoxycarbenium ion pools from thioacetals

Seiji Suga, Kouichi Matsumoto, Koji Ueoka, Jun Ichi Yoshida

Journal of the American Chemical Society 128 ( 24 ) 7710 - 7711 2006.6

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

A sequential one-pot indirect cation pool method has been developed. The method involves the electrochemical generation and accumulation of ArS(ArSSAr)+ at low temperature (step 1) and the follow-up reaction with a thioacetal to generate an alkoxycarbenium ion pool (step 2), which reacts with various carbon nucleophiles (step 3). Steps 2 and 3 are extremely fast. The electrogenerated ArS(ArSSAr)+ was well-characterized by 1H NMR and CSI-MS. The alkoxycarbenium ion pool generated by the present indirect method exhibited 1H and 13C NMR spectra and thermal stability similar to those of the alkoxycarbenium ion pool generated by the direct electrochemical method. Copyright © 2006 American Chemical Society.

DOI： 10.1021/ja0625778

Selective monoiodination of aromatic compounds with electrochemically generated I⁺ using micromixing

Koji Midorikawa, Seiji Suga, Jun Ichi Yoshida

Chemical Communications ( 36 ) 3794 - 3796 2006

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Selective monoiodination of aromatic compounds such as dimethoxybenzene has been successfully achieved with I+, which is generated by anodic oxidation of I2 in acetonitrile, using micromixing. © The Royal Society of Chemistry 2006.

DOI： 10.1039/b607284d

Intramolecular participation in alkoxycarbenium ion pools

Seiji Suga, Shinkiti Suzuki, Jun Ichi Yoshida

Organic Letters 7 ( 21 ) 4717 - 4720 2005.10

Publishing type：Research paper (scientific journal)

(Chemical Equation Presented) Alkoxycarbenium ions having no substituents on the cationic carbon have been accumulated as "cation pools" by the introduction of an ether group in an appropriate position. Intramolecular participation of the ether oxygen is suggested to be responsible for stabilization of the alkoxycarbenium ions. © 2005 American Chemical Society.

DOI： 10.1021/ol051915r

Control of extremely fast competitive consecutive reactions using micromixing. Selective Friedel-Crafts aminoalkylation

Aiichiro Nagaki, Manabu Togai, Seiji Suga, Nobuaki Aoki, Kazuhiro Mae, Jun Ichi Yoshida

Journal of the American Chemical Society 127 ( 33 ) 11666 - 11675 2005.8

Publishing type：Research paper (scientific journal)

Friedel-Crafts reactions of aromatic and heteroaromatic compounds with an N-acyliminium ion pool were studied. The reaction of 1,3,5-trimethylbenzene in a batch reactor gave rise to the selective formation of a monoalkylation product (69%). Presumably, the second alkylation is slower than the first alkylation because of the protonation of the monoalkylation product that decreases its reactivity. The reaction of 1,3,5-trimethoxybenzene, however, gave rise to the formation of both monoalkylation (37%) and dialkylation (32%) products. Disguised chemical selectivity due to faster reaction than mixing seems to be responsible for the lack of selectivity. The use of micromixing was found to be quite effective to solve this problem to increase the selectivity. The monoalkylation product was obtained in 92% yield together with a small amount of the dialkylation product (4%). The reaction with various aromatic and heteroaromatic compounds revealed that the low mono/dialkylation selectivity was observed only for highly reactive aromatics. In such cases, the use of micromixing was quite effective to improve the selectivity. On the basis of micromixing, the selective sequential dialkylation using two different N-acyliminium ions was achieved. CFD simulations using a laminar flow and finite-rate model are consistent with the experimental observations and clearly indicate the importance of mixing. © 2005 American Chemical Society.

DOI： 10.1021/ja0527424

Electrochemical combinatorial organic syntheses using microflow systems

Seiji Suga, Masayuki Okajima, Kazuyuki Fujiwara, Jun Ichi Yoshida

QSAR and Combinatorial Science 24 ( 6 ) 728 - 741 2005.8

Publishing type：Research paper (scientific journal)

The "cation flow" method, in which highly reactive carbocations are generated in the absence of nucleophiles by low temperature electrolysis and are allowed to react with carbon nucleophiles in the microflow system to achieve direct electrooxidative C-C bond formation, has been developed. As an extension of the cation flow method, an electrochemical paired microflow system that involves concurrent anodic generation of carbocations and cathodic generation of carbon nucleophiles followed by their reactions to achieve straightforward C-C bond formation has also been developed. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.

DOI： 10.1002/qsar.200440003

Cycloaddition of "N-Acyliminium ion pools" with carbon-carbon multiple bonds

Seiji Suga, Yamato Tsutsui, Aiichiro Nagaki, Jun Ichi Yoshida

Bulletin of the Chemical Society of Japan 78 ( 7 ) 1206 - 1217 2005.7

Publishing type：Research paper (scientific journal)

N-Acyliminium ion pools, which are generated from α-silyl carbamates, were found to react with a variety of alkenes and alkynes to give the corresponding cycloadducts. The reaction with styrene derivatives gave rise to the formation of a significant amount of polymeric products. The use of micromixing, however, resulted in a significant increase in the yield of the cycloadduct at the expense of the polymer. Mechanistic studies indicated that a concerted mechanism seems to be most likely for alkyl-substituted alkenes, whereas a stepwise mechanism seems to be reasonable for aryl-substituted alkenes. © 2005 The Chemical Society of Japan.

DOI： 10.1246/bcsj.78.1206

Radical addition to "cation pool". Reverse process of radical cation fragmentation

Tomokazu Maruyama, Seiji Suga, Jun Ichi Yoshida

Journal of the American Chemical Society 127 ( 20 ) 7324 - 7325 2005.5

"Cation pool" method based on C-C bond dissociation. Effective generation of monocations and dications

Masayuki Okajima, Seiji Suga, Kenichiro Itami, Jun Ichi Yoshida

Journal of the American Chemical Society 127 ( 19 ) 6930 - 6931 2005.5

Selective organic reactions using microreactors

Jun Ichi Yoshida, Seiji Suga, Aiichiro Nagaki

Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry 63 ( 5 ) 511 - 522 2005.5

Publishing type：Research paper (scientific journal)

Organic reactions using microreactors have attracted significant research interest because of their inherent features such as fast mixing, precise temperature control, and precise residence time control. These features are especially advantages for fast and exothermic reactions, which are difficult to perform using conventional macro-scale batch reactors in a controlled manner. Some examples of such reactions including Friedel-Crafts alkylation, cationic polymerization, and Swern oxidation are described in this article. Other examples are also demonstrated with the special emphasis on multiphase reactions. These examples speak well for the potentiality of microreactors in the enhancement of the ability of organic synthesis to meet demanding expectations in future.

DOI： 10.5059/yukigoseikyokaishi.63.511

Microflow electroorganic synthesis without supporting electrolyte

Roberto Horcajada, Masayuki Okajima, Seiji Suga, Jun Ichi Yoshida

Chemical Communications ( 10 ) 1303 - 1305 2005.3

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