Photocatalytic Cycloaddition of Bis(diphenylphosphino)methane with Alkynes to Access Cyclic Diphosphonium Monoylides

A photocatalytic synthesis of cyclic diphosphonium monoylides from 1,1-bis(diphenylphosphino)methane (dppm) and alkynes is reported. This reaction repurposes readily available dppm, a classic diphosphine ligand, as a substrate for the construction of cyclic P–C–P frameworks. Various alkynes participated in the photocyclization to afford cyclic diphosphonium monoylides. A terminal alkyne substrate led to a hydrolytically labile cyclic diphosphonium product, whose ring opening afforded an acyclic phosphine oxide–phosphonium salt, suggesting a potential skeletal-editing approach from dppm to 1,2-diphosphinoethane-derived structures.