The First Example of Azole-Fused Cyclic Anhydride Reacting in the Castagnoli-Cushman Way

Pyrazole-fused cyclic anhydrides have been employed for the first time as the Castagnoli-Cushman reaction partners to produce hitherto unknown 4-oxo-4,5,6,7-tetrahydropyrazolo[1,5-alpha]pyrazine-7-carboxylates in remarkably convenient and speedy fashion. Attempts to realize the same chemistry with indole and benzimidazole analogues failed.