Asymmetric thermal transformation, a new way to enantiopure biphenyl-bridged titanocene and zirconocene complexes: Efficient catalysts for asymmetricimine hydrogenation

Enantiopure biphenyl-bridged titanocene and zirconocene complexes were obta ined by an asymmetric thermal transformation of the binaphthol complexes fo rmed from the metallocene racemates and subsequent transformation to the co rresponding dichlorides, in practically quantitative yields. Increased rate s of this transformation in the presence of O-2 gas or TEMPO indicate a rad ical reaction mechanism. The biphenyl-bridged titanocene enantiomers give r ise to an efficient asymmetric catalysis for the hydrogenation of cyclic an d noncyclic imines.