Synthetic protocol toward fused pyrazolone derivatives via a Michael addition and reductive ring closing strategy.

A new class of pyrazolo[3,4-c]pyridine-3,7-dione and pyrazolo[3,4-d]azepine-3,7-dione scaffolds was synthesized via a Michael addition and reductive cyclization strategy. These fused heterocycles were accessed from simple starting materials such as nitroolefins and 3-ethoxycarbonyl(methylene)pyrazoline-5-one. The pyrazolo-fused heterocycles were obtained in good overall yields.