Organocatalytic Cascade Reactions: Towards the Diversification of Hydroisochromenes and Chromenes through Two Different Activation Modes

摘要

The organocatalytic enantioselective syntheses of functionalized hydroisochromenes and chromenes by trienamine-mediated [4+2]-cycloadditionucleophilic ring-closing and iminium-ion/aminal-mediated oxa-Michael/ Michaelucleophilic ring-closing with 2-nitroallylic alcohols are presented. The corresponding cycloadducts, with up to five stereocenters, are formed in good yield and excellent enantioselectivities. The synthetic applications of the obtained products have been demonstrated.