研究者詳細 - 菅　誠治

論文 - 菅　誠治

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Enhancement of chemical selectivity by microreactors

Jun Ichi Yoshida, Aiichiro Nagaki, Takeshi Iwasaki, Seiji Suga

Chemical Engineering and Technology 28 ( 3 ) 259 - 266 2005年3月

掲載種別：研究論文（学術雑誌）

This article provides a brief outline of the state of the art reactions using microreactors with special emphasis on the enhancement of product selectivity. The efficient micromixing possible with a short diffusion path increases the product selectivity of competitive parallel reactions and competitive consecutive reactions. This concept has been expanded to control of the molecular weight and molecular weight distribution in carbocationic polymerization. The efficient heat transfer, based on high surface to volume ratios, allows precise temperature control and is also effective for the control of highly exothermic reactions, such as free radical polymerization. © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/ceat.200407127

Living cationic polymerization based on "cation pool" method using microsystem

Aiichiro Nagaki, Jun Ichi Yoshida, Kohsuke Kawamura, Mitsuo Sawamoto, Seiji Suga, Tsuyoshi Ando

2005 AIChE Spring National Meeting, Conference Proceedings 3021 2005年

掲載種別：研究論文（国際会議プロシーディングス）

The cation pool of an N-acyliminium ion was found to serve as an effective initiator of cationic polymerization of vinyl ethers in a microsystem consisting of two micromixers and a micro tube reactor. The polymerization led to very narrow molecular weight distribution (Mw/Mn = 1.14). The molecular weight (Mn) increased linearly with an increase of the amount of the monomer. The carbocationic polymer end was effectively trapped by allyltrimethylsilane. The present observations illustrate the potential of microsystems, in conjunction with the cation pool, to effect polymerization in a highly controlled manner without the deceleration inherent in the dynamic equilibrium between active and dormant species.

Cation pool-initiated controlled/living polymerization using microsystems

Aiichiro Nagaki, Kohsuke Kawamura, Seiji Suga, Tsuyoshi Ando, Mitsuo Sawamoto, Jun Ichi Yoshida

Journal of the American Chemical Society 126 ( 45 ) 14702 - 14703 2004年11月

掲載種別：研究論文（学術雑誌）

The "cation pool" of an N-acyliminium ion was found to serve as an effective initiator of cationic polymerization of vinyl ethers in a microsystem consisting of two micromixers and a microtube reactor. The polymerization led to very narrow molecular weight distribution (Mw/Mn = 1.14). The molecular weight (Mn) increased linearly with an increase in the amount of the monomer. The carbocationic polymer end was effectively trapped by allyltrimethylsilane. The present observations illustrate the potential of microsystems, in conjunction with the cation pool, to effect polymerization in a highly controlled manner without the deceleration inherent in the dynamic equilibrium between active and dormant species. Copyright © 2004 American Chemical Society.

DOI： 10.1021/ja044879k

Three-component coupling based on the "cation pool" method

Seiji Suga, Tomoaki Nishida, Daisuke Yamada, Aiichiro Nagaki, Jun Ichi Yoshida

Journal of the American Chemical Society 126 ( 44 ) 14338 - 14339 2004年11月

掲載種別：研究論文（学術雑誌）

Sequential one-pot three-component coupling reactions have been developed based on the "cation pool" method. An N-acyliminium ion generated by the "cation pool" method adds to an electron-rich carbon-carbon double bond, such as enamine derivatives and vinyl sulfides, to form the second "cation pool". The addition of nucleophiles such as allylsilanes, enol silyl ethers, Grignard reagents, and organoaluminum compounds led to the formation of the corresponding three-component coupling products. Copyright © 2004 American Chemical Society.

DOI： 10.1021/ja0455704

Generation of alkoxycarbenium ion pools from thioacetals and applications to glycosylation chemistry

Shinkiti Suzuki, Kouichi Matsumoto, Kohsuke Kawamura, Seiji Suga, Jun Ichi Yoshida

Organic Letters 6 ( 21 ) 3755 - 3758 2004年10月

掲載種別：研究論文（学術雑誌）

(Chemical Equation Presented) Alkoxycarbenium ions have been generated and accumulated as "cation pools" by the low-temperature electrochemical oxidation of α-phenylthioethers. Although an unsuccessful attempt to accumulate glycosyl cations was made, a one-pot method for electrochemical glycosylation, which involves anodic oxidation of thioglycosides to generate glycosyl cation equivalents followed by their reactions with glycosyl acceptors, has been developed.

DOI： 10.1021/ol048524h

Cationic carbohydroxylation of alkenes and alkynes using the cation pool method

Seiji Suga, Yasuhisa Kageyama, Govindarajulu Babu, Kenichiro Itami, Jun Ichi Yoshida

Organic Letters 6 ( 16 ) 2709 - 2711 2004年8月

掲載種別：研究論文（学術雑誌）

The reactions of an N-acyliminium ion pool with alkenes and alkynes gave γ-amino alcohols and β-amino carbonyl compounds, respectively, after treatment with H2O/Et3N. The present reaction serves as an efficient method for cationic carbohydroxylation of alkenes and alkynes. When vinyltrimethylsilane was used as an alkene, the reaction was highly diastereoselective and served as an access to an enantiomerically pure α-silyl-γ-amino alcohol.

DOI： 10.1021/ol049049q

Generation of carbon free radicals by reduction of the cation pool

Seiji Suga, Shinkiti Suzuki, Tomokazu Maruyama, Jun Ichi Yoshida

Bulletin of the Chemical Society of Japan 77 ( 8 ) 1545 - 1554 2004年8月

掲載種別：研究論文（学術雑誌）

The electrochemical reduction of N-acyliminium ions, which were generated by the "cation pool" method, led to the formation of carbon free radicals. Carbon radicals thus generated underwent homo-coupling reactions and the reactions with activated olefins, such as methyl acrylate. In the latter case, a mechanism involving the addition of a carbon radical to the carbon-carbon double bond, followed by one-electron reduction to give carbanions, has been proposed. The present study opens a new possibility for radical-mediated carbon-carbon bond formation based on the reduction of carbocations.

DOI： 10.1246/bcsj.77.1545

Highly selective friedel-crafts reaction of electrochmemically generated "cation pool" using micromixing

Jun Ichi Yoshida, Aiichiro Nagaki, Seiji Suga

Proceedings - Electrochemical Society 10 141 - 144 2004年

掲載種別：研究論文（国際会議プロシーディングス）

Highly selective Friedel-Crafts monoalkylation, which was intrinsically difficult to be achieved by conventional methods, has been accomplished by micromixing. N-Acyliminium ion generated by the "cation pool" method was used as an alkylating agent and 1,3,5-trimethoxybenzene was used as an aromatic compound. The reaction in a macro-scale batch reactor (magnetic stirring) gave rise to the formation of a mixture of the monoalkylation product and the dialkylation product in ca. 1:1 ratio, but the use of a multilamination-type micromixer led to selective monoalkylation (92% yield). Based on the micromixing, the selective sequential dialkylation using two different alkylating agents was achieved.

"N-acyliminium ion pool" as a heterodiene in [4 + 2] cycloaddition reaction

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

Organic Letters 5 ( 6 ) 945 - 947 2003年3月

掲載種別：研究論文（学術雑誌）

(Matrix presented). An N-acyliminium ion pool was found to undergo cycloaddition reaction with a variety of dienophiles such as alkenes and alkynes. A concerted mechanism seems to be most likely for alkyl-substituted alkenes as suggested by the DFT calculations, whereas a stepwise mechanism plays the major role for aryl-substituted alkenes. It is also noteworthy that the present study demonstrates the potential of the combination of the cation pool method and the micromixing in both mechanistic and synthetic aspects.

DOI： 10.1021/ol0341243

Highly selective Friedel-Crafts monoalkylation using micromixing

Seiji Suga, Aiichiro Nagaki, Jun Ichi Yoshida

Chemical Communications 3 ( 3 ) 354 - 355 2003年

Electroauxiliary-assisted sequential introduction of two carbon nucleophiles on the same α-carbon of nitrogen: Application to the synthesis of spiro compounds

Seiji Suga, Mitsuru Watanabe, Jun ichi Yoshida

Journal of the American Chemical Society 124 ( 50 ) 14824 - 14825 2002年12月

掲載種別：研究論文（学術雑誌）

The sequential introduction of two carbon nucleophiles on the same α-carbon of nitrogen by using selective oxidative cleavage of two silyl groups as electroauxilialies has been accomplished. The combination of this expedient transformation and ring-closing metathesis enables reliable and straightforward syntheses of nitrogen-containing spiro compounds, such as cephalotaxine. Copyright © 2002 American Chemical Society.

DOI： 10.1021/ja028663z

Basic concepts of "cation pool" and "cation flow" methods and their applications in conventional and combinatorial organic synthesis

Jun Ichi Yoshida, Seiji Suga

Chemistry - A European Journal 8 ( 12 ) 2650 - 2658 2002年6月

掲載種別：研究論文（学術雑誌）

Carbocations have been generally considered to be relatively unstable and transient species. But the "cation pool" method enables the easy accumulation of carbocations in conventional reaction media such as dichloromethane. In the "cation pool" method, carbocations are generated by low-temperature electrochemical oxidation and accumulated in a solution. In the next step, the carbocations thus produced are allowed to react with various nucleophiles. Combinatorial parallel synthesis based upon the "cation pool" method has also been developed. The applicability of the "cation pool" method depends upon the stability of the cation that is accumulated. This problem can be overcome by the "cation flow" method. In the "cation flow" method, carbocations are generated in a microflow electrochemical system. Short residence times and efficient temperature control of the microflow system are advantageous. Combinatorial sequential synthesis has been achieved based on the "cation flow" method.

DOI： 10.1002/1521-3765(20020617)8:12<2650::AID-CHEM2650>3.0.CO;2-S

Reduction of a "cation pool": A new approach to radical mediated C-C bond formation

S. Suga, S. Suzuki, J. I. Yoshida

Journal of the American Chemical Society 124 ( 1 ) 30 - 31 2002年1月

掲載種別：研究論文（学術雑誌）

Carbocations, carbon radicals, and carbanions are important reactive carbon intermediates in organic chemistry, and their interconversions can be carried out by redox processes. Although, such relationships have been well recognized, experimental work has been limited to analytical studies on highly stabilized intermediates. In this study such interconversions were examined using electrochemical reduction of "cation pools". Acyliminium cations, which were generated by low-temperature electrolysis of carbamates, were reduced electrochemically in the absence of radical acceptors. The homo coupling products formed effectively, suggesting that the one-electron reduction of the acyliminium cation produced the corresponding carbon-centered radical. Next, the electrochemical reduction of the acyliminium cations in the presence of electron-deficient olefins was examined. The cross coupling products were obtained in good-to-moderate yields. A mechanism involving radical addition to the double bond followed by the reduction of the resulting radical to the carbanion was suggested. The overall transformation serves as redox-mediated formal addition of C-H to C=C. The present strategy opens new opportunities to manipulate reactive carbon species using redox processes in organic synthesis. Copyright © 2002 American Chemical Society.

DOI： 10.1021/ja0171759

Catalytic enantioselective addition of dialkylzincs to aldehydes using (2S)-(-)-3-exo-(dimethylamino)isoborneol [(2S)-daib]: (S)-1-phenyl-1-propanol: [Benzenemethanol, α-ethyl-, (S)-]

Masato Kitamura, Hiromasa Oka, Seiji Suga, Ryoji Noyori, David E. Kaelin, Stephen F. Martin, Gregory L. Beutner, Scott E. Denmark

Organic Syntheses 79 139 2002年

Selective electrochemical oxidation of heteroatom compounds having both silicon and tin on the same carbon as electroauxiliaries

J. I. Yoshida, M. Watanabe, H. Toshioka, M. Imagawa, S. Suga

Journal of Electroanalytical Chemistry 507 ( 1-2 ) 55 - 65 2001年7月

掲載種別：研究論文（学術雑誌）

The selective electrochemical oxidation of heteroatom compounds having two different electroauxiliaries, i.e. silicon and tin, on the same α-carbon was examined. The oxidation potentials of such compounds were found to be similar to those of the corresponding compounds having only tin, indicating the predominant role of tin over that of silicon. The HOMO levels obtained by the molecular orbital calculations were consistent with the experimental results. The molecular orbital calculation of the cation radical suggests the selective cleavage of the C-Sn bond by the oxidation. Preparative electrochemical oxidation gave rise to selective cleavage of the C-Sn bond and the introduction of a nucleophile to the carbon. The C-Si bond was not affected at all. The product can also be further oxidized using the silyl group as an electroauxiliary. The second oxidation proceeded smoothly to cleave the C-Si bond and a second nucleophile was introduced on the same carbon. The present study indicates the feasibility of the redox potential based selective sequential transformation using electroauxiliaries. © 2001 Elsevier Science B.V.

DOI： 10.1016/S0022-0728(01)00402-8

Reaction of an electrogenerated 'iminium cation pool' with organometallic reagents. Direct oxidative α-alkylation and -arylation of amine derivatives

Seiji Suga, Masayuki Okajima, Jun ichi Yoshida

Tetrahedron Letters 42 ( 11 ) 2173 - 2176 2001年3月

掲載種別：研究論文（学術雑誌）

We have developed an efficient direct oxidative α-alkylation and -arylation of carbamates based on the 'cation pool' method. Grignard reagents, organozinc compounds, and organoaluminum compounds are effective as carbon nucleophiles toward iminium cation pools generated by low temperature electrolysis of carbamates. © 2001 Elsevier Science Ltd.

DOI： 10.1016/S0040-4039(01)00128-9

Self and nonself recognition of chiral catalysts: The origin of nonlinear effects in the amino-alcohol catalyzed asymmetric addition of diorganozincs to aldehydes

Ryoji Noyori, Seiji Suga, Hiromasa Oka, Masato Kitamura

Chemical Records 1 ( 2 ) 85 - 100 2001年

掲載種別：研究論文（学術雑誌）

Asymmetric addition of dialkylzincs to aldehydes in the presence of (2S)-3-exo(dimethylamino)isoborneol [(5)-DAIB] exhibits various nonclassical phenomena. The enantiomeric excess (ee) of the alkylation product, obtained with partially resolved DAIB, is much higher than that of the chiral amino alcohol, while the rate decreases considerably as the ee of DAIB is lowered. The asymmetric amplification effects reflect the relative turnover numbers of two enantiomorphic catalytic cycles, where an essential feature is the reversible homochiral and heterochiral dimerization of the coexisting enantiomeric DAIB-based Zn catalysts. The interplay between the thermodynamics of the monomer/dimer equilibration and the kinetics of alkylation reaction strongly affect the overall profile of asymmetric catalysis. The self and nonself recognition of the chiral Zn catalysts is a general phenomenon when (5)-DAIB is mixed with its enantiomer, diastereomer, or even an achiral -amino alcohol. The degree of nonlineariry is highly affected not only by the structures and purity of catalysts but also by various reaction parameters. The salient features have been clarified on the basis of molecular weight measurements, NMR and X-ray crystallographic studies of organozinc complexes, and kinetic experiments, as well as computer-aided quantitative analysis. ©2001 The Jaoan Chemical Tournai Forum and lohn Wilev & Sons. Inc.

DOI： 10.1002/tcr.1.abs

Intramolecular assistance of electron transfer from heteroatom compounds. Electrochemical oxidation of 2-(2-pyridyl)ethyl-substituted ethers, sulfides, and selenides

Mitsuru Watanabe, Seiji Suga, Jun Ichi Yoshida

Bulletin of the Chemical Society of Japan 73 ( 1 ) 243 - 247 2000年1月

掲載種別：研究論文（学術雑誌）

Organoheteroatom compounds having a 2-(2-pyridyl)ethyl group were synthesized and their oxidation potentials were determined by rotating disk electrode voltammetry. The oxidation potentials were found to be less positive than those of the corresponding compounds having a phenyl group in place of the pyridyl group. The dynamic coordination of the pyridyl group to the heteroatom, which stabilizes the cation radical intermediate, seems to be responsible for facilitating the electron transfer. The magnitude of the intramolecular assistance increases along with an increase in the oxidation potential of the parent compounds. This tendency can be explained in terms of the energy match between the nonbonding p orbital of the pyridyl nitrogen and the HOMO of the parent heteroatom compound.

DOI： 10.1246/bcsj.73.243

Direct oxidative carbon-carbon bond formation using the 'cation pool' Method. 1. Generation of iminium cation pools and their reaction with carbon nucleophiles

Jun Ichi Yoshida, Seiji Suga, Shinkiti Suzuki, Naoya Kinomura, Atsushi Yamamoto, Kazuyuki Fujiwara

Journal of the American Chemical Society 121 ( 41 ) 9546 - 9549 1999年10月

掲載種別：研究論文（学術雑誌）

We have developed a method that involves the generation of a 'cation pool' using low-temperature electrolysis, and then its reaction with nucleophiles under non-oxidative conditions. This one-pot method solves problems associated with conventional oxidative generation of cations and their in situ reaction with nucleophiles, and provides an efficient method for direct oxidative carbon-carbon bond formation. As an example of this method, generation of cation pools from carbamates by low-temperature electrolysis (-72 °C) and their reactions with carbon nucleophiles such as allylsilanes, enol silyl ethers, and enol acetates were examined and the desired products were obtained in good yields. Aromatic compounds and 1,3- dicarbonyl compounds can also be utilized as carbon nucleophiles. The present method was also applied to combinatorial parallel synthesis using a robotic synthesizer.

DOI： 10.1021/ja9920112

Control of the free radical reaction by dynamic coordination: Unique reactivity of pyridylethyl-substituted tin hydrides

Seiji Suga, Takao Manabe, Jun Ichi Yoshida

Chemical Communications ( 13 ) 1237 - 1238 1999年7月

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