One-Pot Synthesis of Unsymmetrical Benzils by Oxidative Coupling Using Selenium Dioxide and p-Toluenesulfonic Acid Monohydrate

The oxidative coupling of the a-carbon atom of aromatic ketones with unactivated arenes in the presence of selenium dioxide and p-toluenesulfonic acid monohydrate is described. A number of unsymmetrical benzils have been prepared in good yields (38-75%) with high regioselectivity. The generality and functional tolerance of this new protocol is demonstrated. The mechanistic pathway for the oxidative coupling reaction is also described. The reaction displays superiority in terms of minimization of steps with the C-C bond formation promoted by SeO2 and pTsOH center dot H2O. This method is advantageous as the reactants used as the solvent can be recovered.