Efficient S-Formylation of Thiols with CO2 Catalyzed by Carboxylate Salt Compounds

The formylation of mercaptans using CO2 as a C1 source represents a sustainable and efficient strategy for converting CO2 into value-added chemicals. However, to date, S-formylation still remains scarcely explored with CO2 as the starting material, despite its important role in various biological processes. In this work, the S-formylation reaction between CO2 and mercaptans was successfully carried out to construct C-S bonds using an inexpensive and commercially available carboxylate salt (sodium edetate) as the catalyst under mild conditions (25 °C and 0.1 MPa). Further investigations demonstrated that the present catalytic system applies to a broad substrate scope, affording moderate to excellent yields in the S-formylation of both aliphatic and aromatic thiols with CO2. To clarify the excellent catalytic performance of carboxylates in these S-formylation reactions, reaction intermediates as well as the activating effects of carboxylates on carbon dioxide and phenylsilanes were identified through control experiments and spectroscopic analysis. Based on these findings, the reaction pathway of the S-formylation process was determined, and a corresponding reaction mechanism is proposed.