Photoinduced umpolung addition of carbonyl compounds with α,β-unsaturated esters enables the polysubstituted γ-lactone formation

We herein report the photoinduced intermolecular umpolung addition of aromatic ketones/aldehydes with alpha,beta-unsaturated esters via ketyl radical intermediates. Following an intramolecular transesterification, a variety of gamma-lactone derivatives are readily accessed. Mechanistic investigations demonstrate the significant role of Hantzsch ester, which serves both as the electron and proton donor.