Selective O-Acylation of Ketones with Carboxylic Acids for Enol Esters Synthesis.

Selective O-acylation of ketones with carboxylic acids was disclosed, which produced a wide range of enol esters in good to high yields with Z-configured regioselectivity. This reaction showed high functional group tolerance and could be performed on a gram scale without any decrease of synthetic efficiency. When o-bromobenzoic acids were used, the corresponding enol esters could be easily derivatized into the value-added chromones via Claisen condensation tandem cyclization.