Ir(ppy)3-Catalyzed, Visible-Light-Mediated Reaction of α-Chloro Cinnamates with Enol Acetates: An Apparent Halogen Paradox.

The visible-light-mediated activation of vinyl chlorides derived from α-chloro ethyl cinnamates via oxidative quenching of excited photocatalyst fac-Ir(ppy)3 is described. Upon photoelectron transfer and chloride extrusion, the corresponding vinyl radical can be efficiently trapped by enol acetates, giving rise to synthetically useful 1,4-dicarbonyl compounds in good to excellent yields. This transformation is distinguished by mild and environmentally benign reaction conditions and can be performed on a multigram scale, in sharp contrast to contrasting α-bromo ethyl cinnamates, which show low conversion under the various conditions applied.