Detour of prenostodione synthesis towards pyrazolones for antibacterial activity

Our attempts to prepare indolyl acid (3), enroute to prenostodione (2), from phenyl-hydrazine following a reported procedure of Fischer-Indole synthesis rather lead to ethyl 2-(5-oxo-1-phenyl-2,5-dihydro-1H-pyrazol-3-yl)acetate as a major product, which underwent facile condensation with aldehydes to provide the pyrazolones. Intrigued by the opportunity for the diversity oriented synthesis of substituted pyrazolones, we have developed a facile one pot approach for pyrazolones and screened for antibacterial activity and, herein, results are reported.