Organocatalytic Vinylogous Michael Addition/Cyclization Cascade of 2‐Alkylidene Indane‐1,3‐diones with Enals: A Regio‐ and Stereocontrolled Diversity‐Oriented Route to Indane‐1,3‐dione Derivatives
Jen‐Yu Kuan, I‐Ting Chen, Hsuan Lin, Jeng‐Liang Han
Abstract
Abstract A substrate‐dependent, regio‐ and stereocontrolled diversity‐oriented organocatalytic vinylogous Michael addition/cyclization cascade of 2‐alkylidene indane‐1,3‐diones with enals, using secondary amines as the catalyst, has been developed. This allows the synthesis of spiroindane‐1,3‐diones, tetrahydrofluoren‐9‐one derivatives, and benzofused oxabicyclo[3.3.1]nonanes in a highly selective manner. Plausible catalytic pathways for the formation of these biologically interesting compounds were proposed. Density functional theory (DFT) calculations have clarified and supported the mechanisms how the organocatalyst is able to activate the enals and 2‐hydroxycinnamaldehydes, directing the C−C bond forming with the vinylogous dienolates and enabling the synthesis of these interesting indane‐1,3‐diones derivatives.