Copper(I)-catalyzed [2+2] photocycloaddition of nonconjugated alkenes in room-temperature ionic liquids

Intra- and intermolecular copper(|I)-catalyzed [2+2] photocycloaddition reactions of nonconjugated alkenes can be achieved efficiently in room-temperature ionic liquids such as [tmba][NTf2]. The ionic liquid can be recovered and recycled. No cycloadduct could be isolated when the same reaction is carried out under identical conditions in [bmim][NTf2], which undergoes extensive decomposition.