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Paper | Special issue | Vol 84, No. 2, 2012, pp.1045-1056
Published online, 16th August, 2011
DOI: 10.3987/COM-11-S(P)82
Chiba-G-Catalyzed Intramolecular Oxo-Michael Addition: Synthetic Approaches to Vitamin E Skeleton

Sayaka Tokunou, Waka Nakanishi, Natsuko Kagawa, Takuya Kumamoto, and Tsutomu Ishikawa*

*Graduate School of Pharmaceutical Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan

Abstract

A chroman skeleton with quaternary carbon chiral center, leadable to vitamin E after manipulation, was constructed through 6-exo-trig type intramolecular oxo-Michael addition in up to 44% yield with 81% ee when a phenol with (Z)-α,β-unsaturated ester at ortho position was reacted in the presence of a guanidine-type organocatalyst, Chiba-G [(-)-(4R,5R)-2-[(S)-1-hydroxymethyl-2-phenylethyl]imino-1,3-dimethyl-4,5-diphenylimidazolidine (or the enantiomer)].