Reductive coupling of benzoyl cyanide and carbonyl compounds by aqueous titanium(III) ions. A new convenient and selective access to the less stable mixed benzoins

Abstract

The reactive species formed by the Ti(III) ion reduction of benzoyl cyanide (1) adds to the C-atom of carbonyl compounds 2 under simple experimental conditions. The intermediate 1,2-diols 3 are smoothly converted, without isolation, into the less thermodynamically stable mixed benzoins 4, which are not accessible by the classical benzoin condensation. The possible mechanisms involved in the reaction are discussed