Metal catalyzed asymmetric cyanation reactions

Chiral cyanohydrins are versatile building blocks for pharmaceuticals, agrochemicals and specialty materials. A number of efficient and successful synthetic methods have been developed however, the chiral catalytic method is one of the most attractive strategies where asymmetric addition of different source of cyanide to the carbonyl group of aldehydes and ketones was affected with the help of a chiral metal complex. This review would discuss the various methods for catalytic asymmetric synthesis of cyanohydrins derived from both aldehydes and ketones using different source of cyanide. The emphasis would be given to chiral Lewis acid metal complexes as efficient catalysts for cyanation reaction with the probable mechanism, wherever necessary.