Enantioselective organocatalytic synthesis of the chiral chromenes by domino oxa-Michael-aldol reaction

The proline based chiral organocatalyst has been found to be an efficient catalyst for the facile synthesis of substituted 2-aryl-2H-chromenes-3-carbaldehyde. We envisioned that the iminium interaction between chiral amino catalysts and alpha,beta-unsaturated carbonyl group was beneficial along with thiourea group as hydrogen bond donor, heterocyclic amines as general base in the domino oxa-Michael-aldol reaction. This catalytic system provided the products in good to high yields (73%-96%) with excellent enantioselectivity (up to 97%) and reasonable reaction time. The atom economy, high yield and mild reaction conditions are some of the important features of this protocol. (C) 2017 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.