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 )Cl 2 , but also potentially as a P,P,O-tripodal pincer. As a result, under mild conditions (80 °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 %.