One-pot synthesis of polyfunctionalized 4H-chromenes and dihydrocoumarins based on copper(II) bromide-catalyzed C-C coupling of benzylic alcohols with ketene dithioacetals

Abstract

The synthesis of polyfunctionalized 4Hchromenes 3 and dihydrocoumarins 4 has been developed from the same substrates. Catalyzed by copper(II) bromide (0.3 equiv.), the reactions of the easily available ketene dithioacetals 1 with 2-(hydroxymethyl)phenols 2 lead to 4/7-chromenes 3 in high to excellent yields in dichloromethane solvent, whereas, 3,4-trans-disubstituted dihydrocoumarins 4 are obtained in high yields with high diastereoselectivities by prolonging the reaction time or changing the solvent from dichloromethane to acetonitrile. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.