A convenient and selective synthesis of unsymmetrical benzoins via the cyanide ion catalyzed cleavage of benzils

The cyanide ion-catalyzed cleavage of benzils is used for the generation of various ‘masked’ acyl intermediates. The reaction of these intermediates with various aldehydes furnishes the corresponding esters of unsymmetrical benzoins in very good yields. A variety of unsymmetrical benzoin derivatives are synthesized in this way, including ferrocene derivatives. The hydrolysis of benzoin esters and their subsequent oxidation affords the corresponding unsymmetrical benzoins and benzils in high yield.