The irradiation of chloranil (CA), dissolved in benzene, in the presence of norbornene gave the α,β-unsaturated α,γ-dichloro-γ-lactone 1 in 67% yield. Heretofore, such a product had not been observed in a photochemical reaction of CA with an alkene. In addition, bicyclo[2.1.1]hex-2-ene and cyclopentene furnished compounds such as 1. However, conventional products of the reaction of 3CA with alkenes