Visible‐Light‐Promoted Ring‐Opening Alkynylation, Alkenylation, and Allylation of Cyclic Hemiacetals through β‐Scission of Alkoxy Radicals

The alkoxy radicals that are derived from cyclic hemiacetals have been generated through the visible‐light‐promoted reaction of the corresponding N‐alkoxyphthalimides with Hantzsch ester as the reductant. The alkoxy radicals subsequently undergo β‐scission of the C−C bond to generate carbon‐centered radicals, which are trapped by alkynyl‐, alkenyl‐, or allylsulfones. Ring‐opening alkynylation, alkenylation, and allylation of cyclic hemiacetal derivatives under visible‐light irradiation conditions with Hantzsch ester (HE) as the reductant have been developed. Photoinduced generation of alkoxy radicals, β‐scission, and the trapping of the generated carbon‐centered radicals by alkynyl‐, alkenyl‐, or allylsulfones are involved in these transformations (see scheme).