Preparation of Bicyclopyrazolium Scaffolds and Their Application toward 1,3-Difunctionalization

The strategy employs a formal hydride abstraction process achieved through a stepwise hydrogen atom transfer and oxidative radical–polar crossover process to generate a benzylic carbocation. Capture of the carbocation with pyrazole generates an intermediate <i>N</i>-benzylpyrazole, which undergoes cyclization with a pendant halide to form a fused bicyclic pyrazolium scaffold.

We demonstrate that the pyrazolium structure can serve as an intermediate toward accomplishing 1,3-difunctionalization through further reaction with various nucleophiles.