Pyrrolo[3,4- c]pyrazole Synthesis via Copper(Ι) Chloride-Catalyzed Oxidative Coupling of Hydrazones to Maleimides.

A variety of pyrrolo[3,4- c]pyrazole derivatives from readily available aldehyde hydrazones and maleimides via direct oxidative coupling under radical cascade reaction have been reported. This method offers satisfactory chemical yields and good functional group compatibility. Moreover, this practical approach is catalyzed by CuCl utilizing air as the oxidant and some control experiments were performed to elaborate the mechanism.