Chiral titanium trisphenolate and bisphenolate in enantioselective catalysis

CHED 364

Andrew M. Ullman, ullmana@carleton.edu and Gretchen E. Hofmeister, ghofmeis@carleton.edu. Department of Chemistry, Carleton College, Northfield, MN 55057
The enantioselectivities of chiral titanium trisphenolate and bisphenolate complexes were studied by means of the asymmetric alkylation of benzaldehyde with diethylzinc. We anticipated that chiral binding sites on the metal ligand complex would lead to enantioselective production of 1-phenyl-1-propanol. The enantioselectivities for titanium trisphenolate ranged from 4-8 % ee while titanium bisphenolate showed 8-16 % ee. These low values suggest that the active catalyst in solution is different from that predicted or that the chiral coordination site at titanium is not selective.