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 delta,& varepsilon;- or gamma,delta-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, beta-fragmentation of alkoxy radicals, single electron transfer oxidation, and deprotonation. It provides a good complementary approach to the existing desaturation protocols. A visible light photocatalytic formyl group migration-triggered remote desaturation is realized, producing a library of functionalized trifluoromethylated delta,& varepsilon;- or gamma,delta-unsaturated aldehydes in moderate to excellent yields with good functional group tolerance. The controllable installation of three functional groups, such as CF3, CHO, and a C-C double bond, provides a very attractive protocol for rapid synthesis of complex molecules from simple starting materials. image