Influence of the Cn Symmetry of Chiral Catalyst on the Enantioselectivity of Reactions

Relationship between enantioselectivity of asymmetric reactions and Cn symmetry of chiral metal complexes, as catalysts, has been analyzed in the case of monofunctionalized (one-point binding) substrates. It has been found that effective reactions (ee up to >99%) go through nonsymmetric (asymmetric) intermediate complex responsible for asymmetric induction. If important intermediate retains the C2 or C3 symmetry of initial catalytic complex, enantioselectivity (ee of the product) should be relatively small. Enantioselectivities of the catalytic reactions which deal with three- or two-point binding substrates are independent of C1 or C2 symmetry of initial catalytic complex. These reactions will proceed with high enantioselectivities (up to >99% ee) in both cases. The reasons for all phenomena are discussed.