Active Site Design in a Chemzyme: Development of a Highly Asymmetric and Remarkably Temperature-Independent Catalyst for the Imino Aldol Reaction.

Abstract

Unusually robust: A remarkably temperature-independent catalyst has been developed for the imino aldol reaction of imines derived from ortho-aminophenols. This catalyst is prepared from two equivalents of the VAPOL ligand and a zirconium tetraalkoxide. From a consideration of likely intermediates in the catalytic cycle it was deduced that a methyl substituent ortho to the phenol (R1 ) should enhance induction. This resulted in asymmetric inductions in excess of 98 % ee at room temperature as well as at 100°C. TMS=trimethylsilyl.