Stereodivergent organocatalytic intramolecular michael addition/ lactonization for the asymmetric synthesis of substituted dihydrobenzofurans and tetrahydrofurans

Abstract

A stereodivergent asymmetric Lewis base catalyzed Michael addition/lactonization of enone acids into substituted dihydrobenzofuran and tetrahydrofuran derivatives is reported. Commercially available (S)-(-)-tetramisole hydrochloride gives products with high syn diastereoselectivity in excellent enantioselectivity (up to 99:1 d.r. syn/anti, 99% eesyn), whereas using a cinchona alkaloid derived catalyst gives the corresponding anti-diastereoisomers as the major product (up to 10:90 d.r.syn/anti, 99% eeanti). You can have it both ways! A stereodivergent asymmetric Lewis base catalyzed Michael addition/lactonization of enone acids into substituted dihydrobenzofuran and tetrahydrofuran derivatives is reported, giving products with high d.r. and ee (see scheme). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.