Copper-catalyzed oxidation of azolines to azoles

We report herein convenient, aerobic conditions for the oxidation of thiazolines to thiazoles and data regarding the oxidation mechanism. These reactions feature operationally simple and environmentally benign conditions and proceed in good yield to afford the corresponding azoles, thus enabling the inexpensive preparation of valuable molecular building blocks. Incorporation of a novel diimine-ligated copper catalyst, [((Mes)DAB(Me))Cu-II(OH2)(3)](2+) [-OTf](2), provides increased reaction efficiency in many cases. In other cases copper-free conditions involving a stoichiometric quantity of base affords superior results.