Selective oxidation of benzoins with chromic acid supported on silica gel under viscous conditions

An efficient route for the oxidation of benzoins to corresponding benzils using chromic acid supported on silica gel reagent under viscous conditions at room temperature is described. All the reactions are completed within 4 h in yields between 86-91%. The present procedure can overcome the problems existed in the common solvent-free reactions of the difficulty for the solid molecular collision to react. In addition, due to the reaction using a very minimum amount of solvents, combustion, toxicity, and environmental pollution of the solvents are quite reduced.