Photoinduced selective hydrophosphinylation of allylic compounds with diphenylphosphine oxide leading to γ-functionalized P-ligand precursors

A series of bifunctional phosphine compounds promising as γ-functionalized phosphine ligand precursors are conveniently synthesized by the radical addition of diphenylphosphine oxide (Ph₂P(O)H) to allylic compounds under photoirradiation. The photoinduced addition proceeds regioselectively in an anti-Markovnikov manner, and phosphines having hydroxy, alkoxy, aryloxy, acyloxy, and thio groups at the γ-position can be prepared by simple operation. Interestingly, novel continuous addition of Ph₂P(O)H to two molecules of allylic ethers and related compounds is also observed, although their yields are moderate. The substituent and steric effects of the allylic substituents on the radical addition are discussed in detail.