Enantioselective synthesis of Benzofurans bearing adjacent quaternary and tertiary carbon stereocenters by Organocatalytic asymmetric Michael addition of 3-methylbenzofuran-2(3H)-ones to azadienes

An enantioselective Michael addition of 3-methylbenzofuran-2(3H)-ones to azadienes catalyzed by an L-tert- leucine derived squaramide catalyst was developed, by which a variety of benzofuranones bearing adjacent quaternary and tertiary carbon centers were obtained in high yields (up to 98%) with moderate to excellent diastereoselectivities (up to 97:3) and enantioselectivities (up to 97%).