Analysis of the mechanism of asymmetric amplification by chiral auxili trans-1,2-diaminocyclohexane bistriflamide

Kouichi Asakura, Yuuki Isoda, Dilip K. Kondepudi, Tomohiko Yamaguchi

研究成果: Article査読

抄録

Asymmetric amplification is a phenomenon in which the enantiomeric excess (ee) of a product is higher than that of a chiral auxiliary for a catalyst. We analyzed the mechanism of asymmetric amplification observed in the addition of diethyizinc (Et2Zn) to benzaldehyde (PhCHO) to synthesize 1-phenyl-1-propanol in the presence of trans-1,2-diaminocyclohexane bistriflamide (DCBF) and titanium tetraisopropoxide (TIOP). In a manner similar to the reaction in which 1-piperidino-3,3-dimethyl-2-butanol is a chiral auxiliary for the catalyst, when asymmetric amplification was observed, the ee of the product varied as the reaction progressed. The mechanisms of variation in ee in the two reactions, however, were different. No asymmetric amplification was observed when TIOP and PhCHO were added to a mixture of DCBF and Et2Zn, while the ee of the product was always higher than that of DCBF when PhCHO and Et2Zn were added to a mixture of DCBF and TIOP. In the latter case, the product ee decreased as the reaction progressed. The results indicate that DCBF forms inactive heterochiral complex causing an increase in the ee of DCBF in the solution, which is the chiral auxiliary for the catalyst. But the complex is not very stable and gradually dissociates due to the reaction with Et2Zn. As a result, the asymmetric amplification decreases as the reaction progresses.

本文言語English
ページ(範囲)919-923
ページ数5
ジャーナルChirality
20
8
DOI
出版ステータスPublished - 2008 8 1

ASJC Scopus subject areas

  • 分析化学
  • 触媒
  • 薬理学
  • 創薬
  • 分光学
  • 有機化学

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