Substrate‐Controlled Organocatalytic Divergent Annulations of γ, γ’‐Alkylidene Indane‐1,3‐Diones With Enals

A substrate‐dependent, regio‐ and stereo‐controlled diversity‐oriented organocatalytic vinylogous Michael addition/cyclization cascade of γ, γ’‐alkylidene indane‐1,3‐diones with enals, using secondary amines as the catalyst has been developed. These present methodologies allow the synthesis of chiral 5‐aryl cyclohexenone derivatives 5 , bicyclic 3.3.1 acetal‐fused indane‐1,3‐diones 6 , and spiroindane‐1,3‐diones 7 in a highly selective manner. Plausible catalytic pathways for the formation of these indane‐1,3‐dione derivatives were proposed. Density functional theory (DFT) calculations have clarified and supported how the organocatalyst is able to activate the diethyl‐substituted indane‐1,3‐diones 3 and enals 2 , and an unusual organocatalytic vinylogous Michael addition/dual‐oxa Diels–Alder mechanism occurred to obtain 6 .