Relationship between structure and efficiency of atropisomeric phosphine ligands in homogeneous catalytic asymmetric hydrogenation~?

摘要

A relationship between the structure of biaryl atropisomeric diphosphine ligands and their efficiency in model rhodium catalyzed asymmetric catalytic hydrogenation reactions have been studied with an attempt to separate the two main factors influencing the performance of the ligand in the catalyst core namely, the steric and the electronic factors. A series of new biaryl atropisomeric bisphosphines with only one substituent varied in its electron-donating versus electron-withdrawing ability placed in a position that should in principle not affect the ligand conformation was designed and synthesized for this purpose. Screening of these ligands in model rhodium catalyzed asymmetric hydrogenations revealed that both yields and especially optical purities of the obtained products are in a clear-cut relationship with the nature of the single substituent varied in the ligand structure.