Dimethylsilyl ketene acetal as a nucleophile in asymmetric Michael reaction: enhanced enantioselectivity in oxazaborolidinone-catalyzed reaction.
[reaction: see text] Dimethylsilanyl [Me2Si(H)] ketene S,O-acetal 6b is an effective nucleophile that retards the undesirable Si+-catalyzed racemic pathway in the oxazaborolidinone-catalyzed asymmetric Michael reaction. Through the further suppression of the Si+-catalyzed pathway by carrying out the reaction in the presence of 2,6-diisopropylphenol and t-BuOMe as additives, enantioselectivity up to 98% ee could be achieved for a variety of acyclic enones.
Harada
Toshiro
T
Department of Chemistry and Materials Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan. harada@chem.kit.ac.jp
Adachi
Shinya
S
Wang
Xiaowei
X