Synthesis of 3-HCF2S-Chromones through Tandem Oxa-Michael Addition and Oxidative Difluoromethylthiolation.

A simple protocol for the synthesis of difluoromethylthiolated chromen-4-ones using elemental sulfur and ClCF2CO2Na as the difluoromethylthiolating agent is described. Three-component reactions of 2'-hydroxychalcones, ClCF2CO2Na, and sulfur under basic conditions using TEMPO as the oxidant afforded HCF2S-containing 4H-chromen-4-one and 9H-thieno[3,2-b]chromen-9-one derivatives in good yield. The protocol is practical and efficient, and the starting materials are cheap and readily available.