CATALYTIC ASYMMETRIC HYDROGENATION OF IMINES WITH A CHIRAL TITANOCENECATALYST - SCOPE AND LIMITATIONS

The asymmetric hydrogenation of imines with a chiral titanocene cataly st derived from Brintzinger's ansatitanocene complex 1 proceeds to aff ord amines with good to excellent enantioselectivity. The catalyst is particularly effective for the reduction of cyclic imines. For these s ubstrates enantiomeric excesses from 95 to 99% were achieved. For acyc lic imines lower enantiomeric excesses were observed. The reason for t his is likely due to the fact that the acyclic imines are mixtures of anti and syn isomers which interconvert during the reaction. The catal yst was found to be tolerant of many functional groups found in organi c synthesis. Thus the reaction represents an effective method for the synthesis of chiral cyclic amines.