Novel bis-P,O-hybrid-ligand modified Pd-catalyst for highly selective anti-Markovnikov alkoxycarbonylation of alkenes under mild conditions

A series of bis-P,O-hybrid ligands (L1-L4) were synthesized and characterized. The crystal structures demonstrated that the ligand of L2, 1,4-bis((2-(diphenylphosphaneyl)phenoxy)methyl)benzene, not only acted as a typical trans-positioned diphosphine as observed in the complexes Pd(L2)(OAc)2 and Pd(L2)Cl2, but also potentially as a P,P,O-tripodal pincer. As a result, under mild conditions (80 degrees C, 0.5-3.0 MPa), L2 enabled Pd (OAc)2 to exhibit remarkable performance in terms of high activity and excellent regioselectivity (l/b > 97/3) in the alkoxycarbonylation of vinyl arenes with the isolated yields of 57-91 %.