Asymmetric Synthesis of Chiral Spiroketal Bisphosphine Ligands and Their Application in Enantioselective Olefin Hydrogenation

摘要

A series of chiral spiroketal bisphosphine ligands containing 1,1'-spirobi(3H,3'H)isobenzofuran back-bones was accessed through asymmetric synthesis and subsequently tested in enantioselective Rh-catalyzed hydro-genation of alpha-dehydroamino acid esters. The ligand providing the highest enantioselectivity (up to 99.5%) was obtained in seven steps in an overall 38% yield. The synthesis could be performed on a gram scale, and no kinetic resolution of enantiomers is required. Overall, the developed ligand provides an easily accessible alternative to SDP ligands as well as other chiral bisphosphine ligands.