Showing papers by "Seiji Suga published in 2005"
TL;DR: In this paper, a brief outline of the state of the art of reactions using microreactors with special emphasis on the enhancement of product selectivity is provided. But the authors do not consider the use of micro-reactors in the control of the molecular weight and molecular weight distribution in carbocationic polymerization.
Abstract: This article provides a brief outline of the state of the art of 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.
196 citations
TL;DR: The reaction with various aromatic and heteroaromatic compounds revealed that the low mono/dialkylation selectivity was observed only for highly reactive aromatics, and the use of micromixing was found to be quite effective to improve the selectivity.
Abstract: 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 hig...
182 citations
TL;DR: Anodic methoxylation of several organic compounds has been successfully achieved in the absence of intentionally added supporting electrolyte using an electrochemical microflow system.
121 citations
TL;DR: The "cation pools" of alkoxyarylcarbenium ions were effectively generated by the oxidative C-C bond dissociation using low temperature electrolysis, which is especially effective for the generation and accumulation of dications, which react with carbon nucleophiles.
Abstract: The "cation pools" of alkoxyarylcarbenium ions were effectively generated by the oxidative C-C bond dissociation using low temperature electrolysis. The present method is especially effective for the generation and accumulation of dications, which react with carbon nucleophiles.
63 citations
TL;DR: In this paper, an extension of the cation flow method, an electrochemical paired microflow system that involves concurrent anodic and cathodic generation of carbocations and carbon nucleophiles followed by their reactions to achieve straightforward C-C bond formation has been developed.
Abstract: 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.
62 citations
TL;DR: In this article, 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.
Abstract: 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 he reasonable for aryl-substituted alkenes.
56 citations
TL;DR: The reaction of an N-acyliminium ion with an alkyl iodide and hexabutyldistannane took place to give the alkylation product.
Abstract: The reaction of an N-acyliminium ion with an alkyl iodide and hexabutyldistannane took place to give the alkylation product. A mechanism involving the addition of an alkyl radical to an N-acyliminium ion to produce the corresponding radical cation has been suggested.
52 citations
TL;DR: Intramolecular participation of the ether oxygen is suggested to be responsible for stabilization of the alkoxycarbenium ions.
23 citations
TL;DR: Some examples of such reactions including Friedel-Crafts alkylation, cationic polymerization, and Swern oxidation are described in this article, with the special emphasis on multiphase reactions.
Abstract: 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.
16 citations
TL;DR: In this article, anodic methoxylation of several organic compounds has been successfully achieved in the absence of intentionally added supporting electrolyte using an electrochemical microflow system, without the need to add supporting electrolytes.
Abstract: Anodic methoxylation of several organic compounds has been successfully achieved in the absence of intentionally added supporting electrolyte using an electrochemical microflow system.
10 citations
TL;DR: In this paper, an extension of the cation flow method, an electrochemical paired microflow system that involves concurrent anodic and cathodic generation of carbocations and carbon nucleophiles followed by their reactions to achieve straightforward C-C bond formation has been developed.
Abstract: 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.
Patent•
28 Dec 2005TL;DR: In this article, the authors proposed a method for producing an aromatic iodide, characterized in that an aromatic compound and an active iodinating agent are fed into a flow reactor equipped with a high-speed mixer and hydrogen atom on the aromatic ring of said aromatic compound is continuously substituted by iodine atom.
Abstract: The present invention is directed to provide a means, which enables production of a product superior in color tone in high yield by using an easy-to-handle and highly safe technique, in a method for producing an aromatic iodide. The present invention relates to a method for producing an aromatic iodide, characterized in that an aromatic compound and an active iodinating agent are fed into a flow reactor equipped with a high-speed mixer and hydrogen atom on the aromatic ring of said aromatic compound is continuously substituted by iodine atom.
Patent•
28 Dec 2005TL;DR: In this article, a flow-through type reactor equipped with a high-speed mixer is used to replace hydrogen atoms of the aromatic nucleus of the compound with iodine atoms, and the reaction product having an excellent color tone can be produced in a high yield.
Abstract: A process for producing an aromatic iodine compound. It has advantages of ease of handling and high safety. By the process, the reaction product having an excellent color tone can be produced in a high yield. The process for aromatic iodine compound production is characterized by introducing an aromatic compound and an active iodizing agent into a flow-through type reactor equipped with a high-speed mixer to continuously replace hydrogen atoms of the aromatic nucleus of the aromatic compound with iodine atoms.
TL;DR: In this article, an N-acyliminium ion generated by thecation pool method adds to an electron-rich carbon−carbon double bond, such as enamine derivatives and vinyl sulfides, to form the second "cation pool" to create the corresponding three-component coupling products.
Abstract: 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.
TL;DR: In this article, 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.
Abstract: 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 he reasonable for aryl-substituted alkenes.
TL;DR: In this paper, a one-pot method for electrochemical glycosylation, which involves anodic oxidation of thioglycosides to generate glyco-cation equivalents followed by their reactions with glyco acceptors, has been developed.
Abstract: [reaction: see text] Alkoxycarbenium ions have been generated and accumulated as "cation pools" by the low-temperature electrochemical oxidation of alpha-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.
TL;DR: The reaction of an N-acyliminium ion with an alkyl iodide and hexabutyldistannane took place to give the alkylation product as discussed by the authors.
Abstract: The reaction of an N-acyliminium ion with an alkyl iodide and hexabutyldistannane took place to give the alkylation product. A mechanism involving the addition of an alkyl radical to an N-acyliminium ion to produce the corresponding radical cation has been suggested.
TL;DR: Some examples of such reactions including Friedel-Crafts alkylation, cationic polymerization, and Swern oxidation are described in this paper, with the special emphasis on multiphase reactions.
Abstract: 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.
TL;DR: In this paper, the "cation pools" of alkoxyarylcarbenium ions were effectively generated by the oxidative C-C bond dissociation using low temperature electrolysis, which was especially effective for the generation and accumulation of dications, which react with carbon nucleophiles.
Abstract: The "cation pools" of alkoxyarylcarbenium ions were effectively generated by the oxidative C-C bond dissociation using low temperature electrolysis. The present method is especially effective for the generation and accumulation of dications, which react with carbon nucleophiles.