Photocatalytic carboxylation of alkenes via synergistic <sc>hydrogen-atom </sc>transfer and proton transfer

A visible-light-induced synergistic hydrogen atom transfer (HAT) and proton transfer (PT) catalysis was developed for the defluorinative carboxylation of α-CF2R-substituted alkenes. This system affords a variety of γ,γ-difluoro- and γ-monofluoro-vinylacetic acids without stepwise acidification, exhibiting good functional group tolerance, broad scope, and facile scalability. Mechanism studies support that thiol plays the role of the hydrogen relay, which s a hydrogen atom through HAT and then outputs a proton via PT. This strategy also takes full advantage of formate for photocatalytic carboxylation reaction in a step- and atom-economical way.