Visible-light-driven thio-carboxylation of alkynes with CO2: facile synthesis of thiochromones

Difunctionalizing carboxylation of alkynes with CO2 is a sustainable and important strategy to generate valuable acrylate derivatives from both readily available starting materials. Such protocols, however, always suffer the use excess metallic reagents transition metal residue. Herein, we report first thio-carboxylation thiophenols CO2, which visible-light-driven metal-free process. In contrast previous carboxylations via two-electron activation mechanistic computational investigations suggest that single-electron involved in thio-carboxylation, rendering unique β-carboxylation. The following cyclizing acylation affords thiochromones efficiently. Moreover, one-pot method features mild reaction conditions (room temperature, 1 atmosphere CO2), high chemo- regio-selectivity, easy scalability facile derivatization products bioactive compounds.