Lewis acid-promoted cross aldol reaction of aldehydes with ketones utilizing 3-methyl-2-phenyl-2-(2-oxoalkyl)benzothiazolines as an enolate-transferring reagent.

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概要

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• The treatment of a variety of 3-methyl-2-phenyl-2-(2-oxoalkyl)benzothiazolines with aldehydes in the presence of 2 equivalents of SnCl<SUB>4</SUB> in dichloromethane at −78°C underwent a carbon–carbon bond cleavage at the 2-position of the benzothiazoline ring releasing an 2-oxoalkyl moiety followed by the concurrent aldol-type reaction with aldehydes to afford the corresponding β-hydroxy ketones. Among the Lewis acids examined, SnCl<SUB>4</SUB> was found to be most effective, while a similar reaction employing trimethylsilyl trifluoromethanesulfonate as an electrophilic promoter mainly gave the corresponding aldol-condensation product. In the case of the reaction with 3-methyl-2-phenyl-2-(1-substituted 2-oxoalkyl)benzothiazolines, a diastereomeric mixture of α-substituted β-hydroxy ketones as cross aldol products was obtained and the anti preference was generally observed for reactions with the benzothiazolines possessing an aromatic ketone moiety in modest to poor selectivity ranging between 69:31 and 57:43. In contrast to this, the reaction of the benzothiazoline possessing an alkyl ketone moiety, 3-methyl-2-phenyl-2-(1-methyl-2-oxobutyl)benzothiazoline, with benzaldehyde showed syn preference in modest selectivity of 70:30.

• 公益社団法人 日本化学会の論文

著者

• Chikashita Hidenori

  Department Of Applied Chemistry Faculty Of Engineering Kansai University

• Itoh Kazuyoshi

  Department Of Applied Chemistry Faculty Of Engineering & High Technology Research Center Kansai

• Yamada Seiji

  Department of Applied Chemistry, Faculty of Engineering, Kansai University

• Tame Shin-ichiro

  Department of Applied Chemistry, Faculty of Engineering, Kansai University

• Itoh Kazuyoshi

  Department of Applied Chemistry, Faculty of Engineering, Kansai University

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