Metal-Catalyzed Kinetic Resolution Processes

A large variety of metal-based chiral complexes have been developed in the past twenty five years that allow for the effective catalytic resolution of an impressive range of racemic compounds. After the initial discovery of Ti-catalyzed kinetic resolution of allylic alcohols by Sharpless and coworkers in the early eighties, a number of other transformations have emerged that may be used for catalytic resolution. Amongst them are the Ru-catalyzed hydrogenation, the Zr-catalyzed carbomagnesation, the Mn-catalyzed epoxidation, the Co-catalyzed epoxide hydrolysis, and the Ti-catalyzed reduction of C=N and C=0 bonds. Most recently, the Mo-catalyzed ring-closing metathesis has been utilized to catalytically resolve organic molecules in an efficient manner. This article provides a brief overview of these and other major developments in metal-catalyzed kinetic resolution; strengths and weaknesses of various methods are discussed, and different protocols that afford identical or similar optically pure or enriched compounds are compared. Where possible, the available mechanistic paradigms that affords a rationale as to the observed stereochemical outcomes are provided.