Synthesis of 3-HCFS-Chromones through Tandem Oxa-Michael Addition and Oxidative Difluoromethylthiolation.

A simple protocol for the synthesis of difluoromethylthiolated chromen-4-ones using elemental sulfur and ClCFCONa as the difluoromethylthiolating agent is described. Three-component reactions of 2'-hydroxychalcones, ClCFCONa, and sulfur under basic conditions using TEMPO as the oxidant afforded HCFS-containing 4-chromen-4-one and 9-thieno[3,2-]chromen-9-one derivatives in good yield. The protocol is practical and efficient, and the starting materials are cheap and readily available.