RHAT-Enabled Deoxyfunctionalization of Cyclic Acetals Derived from Vicinal Diols.

The selective activation and functionalization of robust C(sp)─O bonds in diols remains a formidable challenge in organic synthesis due to their high bond dissociation energies and poor leaving group properties. In this study, we report a regioselective radical deoxygenative strategy for the functionalization of six-membered and larger cyclic acetals derived from vicinal diols, leading to the synthesis of deconjugated alkenes under mild, visible-light-driven conditions. The methodology exhibits broad substrate scope with respect to both cyclic acetals and alkynes, delivering a variety of deconjugated alkene products in moderate to excellent yields and with high regioselectivity. Mechanistic studies, including radical trapping, isotopic labeling, and density functional theory (DFT) calculations, provide strong evidence for a sequential regioselective hydrogen atom transfer (RHAT)/radical addition/RHAT/C─O cleavage sequence. This work introduces a new platform for the site-selective functionalization of vicinal diols and highlights the potential of RHAT-enabled strategies in C─O bond activation.