Visible‐Light‐Driven Formyl Group Migration Triggered Remote Desaturation.

Dehydrogenation of unactivated alkanes to form versatile alkenes is an important but challenging task in synthetic chemistry. Enabled by a radical‐mediated formyl group migration, a novel visible light‐induced remote desaturation of aldehydes is developed, delivering a panel of trifluoromethylated δ,ϵ‐ or γ,δ‐unsaturated aldehydes in moderate to excellent yields with good functional group tolerance at room temperature. Mechanistic studies indicate a reaction pathway comprising the cascade trifluoromethylation of C−C double bonds, intramolecular addition to aldehydes, β‐fragmentation of alkoxy radicals, single electron transfer oxidation, and deprotonation. It provides a good complementary approach to the existing desaturation protocols. [ABSTRACT FROM AUTHOR]