Enantioselective synthesis of the tetrahydro-6H-benzo[c]chromenes via Domino Michael-Aldol condensation:control of five stereocenters in a quadruple-cascade organocatalytic multi-component reaction

摘要

Organocatalytic domino oxa-Michael-Michael-Michaei-aldol condensation of 2-((E)-2-nitrovinyl)phenol and 2 equiv of alpha,beta-unsaturated aldehydes(e.g.,cinnamaldehyde)provided tetrahydro-6H-benzo[c]chromenes in high diastereoselectivity and high enantioselectivity(>99% ee).Structure of the adduct 4a was confirmed unambiguously by X-ray analysis.The diversity of the protocol was demonstrated by the chemo-differentiating three-component reactions(ABC type)affording the highly func-tionalized tetrahydro-6H-benzo[c]chromenes.