Photo-induced carboxylation of C(sp2)-S bonds in aryl thiols and derivatives with CO2.

Aryl thiols have proven to be a useful class of electron donors and hydrogen atom sources in photochemical processes. However, the direct activation and functionalization of C(sp2)-S bonds in aryl thiols remains elusive in the field of photochemistry. Herein, a photochemical carboxylation of C(sp2)-S bonds in aryl thiols with CO2 is reported, providing a synthetic route to important aryl carboxylic acids. Moreover, different kinds of aryl thiol derivatives, benzeneselenol and diphenyl diselenide also show moderate-to-high reactivity in this transformation. Mechanistic studies, including DFT calculations, suggest that the in situ generated carbon dioxide radical anion (CO2•-) and disulfide might be the key intermediates, which undergo radical substitution to yield products. This reaction features mild and catalyst-free conditions, good functional group tolerance and wide substrate scope. Furthermore, the efficient degradation of polyphenylene sulfide highlights the usefulness of this methodology.