Mannich-Type Reactions Catalyzed by Air-Stable Hf-BINOL Complex

Significance

The authors have previously reported that a zirconium complex derived from BINOL and imidazole derivatives catalyzed the asymmetric Mannich reaction (J. Am Chem. Soc. 2005, 127, 15528). This report describes an air-stable hafnium complex which catalyzes asymmetric Mannich-type reactions of silyl ketene acetals and thioacetals. An X-ray structure of the complex shows Hf₄(µ-BINOLate)₆(µ₃-OH)₄, indicating the presence of four hexa-coordinated Hf atoms and six BINOL ligands. The authors state that this structure is very similar to that obtained from the corresponding zirconium complex.