Catalytic Deoxygenative Transformation of Ketoacids/Esters for the Synthesis of Coumarin, Benzofuranone, and Dihydrobenzo[b]oxepin‐2(3H)‐one Derivatives.

We disclose herein a triflic acid and silane‐promoted reductive deoxygenative transformation of ketoacid/esters for the divergent synthesis of different‐sized lactones, which hold substantial significance in pharmaceutical and natural product chemistry. Owing to the simple reaction conditions and setup, this protocol features broad substrate generality, scalability, and good functional group tolerance, including late‐stage functionalization of pharmaceutical compounds and natural products. The control experiments and detailed NMR study provide insight into the reaction mechanism.