A series of electronically deficient atropisomeric bisphosphine
ligands have been synthesized from (S)-MeO-BiPhep.
The introduction of electron-withdrawing groups in the
ligands had a dramatic influence on both the enantioselectivity
and the activity of catalyst. The iridium complex of the MeO-BiPhep-based
ligand bearing a trifluoromethanesulfonyl group was successfully
applied in the asymmetric hydrogenation of quinolines with ee values
of up to 95% and turnover numbers (TON) of up to 14,600.
iridium - asymmetric hydrogenation - electron-deficient ligands - quinolines