Base-Promoted Direct Cascade Transformation of Chromones to Coumarins via Benzannulation and Transesterification

A mild base-promoted reaction between 3-substituted chromones and beta-keto esters for the easy access to various coumarins with structural diversity is described. This protocol provides highly functionalized 3-acyl-4-arylcoumarins in good-to-excellent yield via benzannulation and transesterification. A reaction mechanism containing Michael addition, 1,5-H shift and intramolecular transesterification is proposed.

Automated summary

A mild base-promoted reaction between 3-substituted chromones and beta-keto esters is described for the easy access to various coumarins. The protocol provides highly functionalized 3-acyl-4-arylcoumarins in good-to-excellent yield via benzannulation and transesterification, with a proposed reaction mechanism involving Michael addition, 1,5-H shift, and intramolecular transesterification.