Organocatalytic β,γ-Selective Activation of Deconjugated Butenolides Access to Chiral Tricyclic Chroman-butyrolactones.

A highly efficient method for the β,γ-selective activation of deconjugated butenolides has been developed through an organocatalytic asymmetric vinylogous cascade reaction. This protocol enables the construction of a broad range of substituted tricyclic chroman-butyrolactones by vinylogous Michael/oxa-Michael pathways in good yield (up to 89%) with good to high enantioselectivity (up to 97:3 er) and excellent diastereoselectivity. The ring-opening esterification of butyrolactones was also demonstrated.