Organocatalytic Enantioselective Michael Addition of 4‐Hydroxycoumarin to α,β‐Unsaturated Ketones: A Simple Synthesis of Warfarin

A type of C2‐symmetric secondary amine amide catalysts were developed for the asymmetric Michael addition of 4‐hydroxycoumarin to α,β‐unsaturated ketones. A series of important biologically and pharmaceutically active compounds were obtained in excellent yields (up to 99 %) with high enantioselectivities (up to 89 % ee) under mild conditions. In addition, enantiopure product could be obtained by a single recrystallization. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)