A Ruthenium-Catalyzed, Novel and Facile Procedure for the Conversion of Vicinal Dihaloalkenes to α-Diketones

Abstract

The plenitude of functional groups along with the vast array of methodologies to create, interconvert and utilize them in a variety of bond forming reactions serve as an important asset for designing chemical synthesis of any target molecule. The α-diketones, a powerful assembly of two adjacent carbonyl groups, are of great interest because of their wide ranging applications. α-Diketones exhibit interesting photochemistry, used as flavorants, serve as precursors for ligands in transition metal chemistry, used in the preparation of variety of heterocycles and natural products. α-Diketones also function as the key elements in the Weiss reaction and in the construction of rigid molecular assemblies (molecular wires, rods, etc.) based on ‘block’ chemistry. Some of the common methods to obtain α-diketones are: (i) oxidation of αhydroxyketones, (ii) oxidation of alkynes, and (iii) oxidation of α-methylene ketones. Although controlled oxidation of alkenes is difficult, KMnO4/Ac2O was reported to give low to moderate yield of α-diketone along with side products. However, the method is not suitable for small cyclic (below cyclooctene) and bicyclic systems. It transpired to us that vicinal dihaloalkenes could serve as masked α-diketones (Scheme 1). We particularly chose