A facile four-component sequential protocol in the expedient synthesis of novel 2-aryl-5-methyl-2,3-dihydro-1H-3-pyrazolones in water and their antitubercular evaluation.

A series of 2-aryl-5-methyl-2,3-dihydro-1H-3-pyrazolones has been synthesized by one-pot, four-component sequential reactions of phenylhydrazine, methyl acetoacetate, aromatic aldehydes and β-naphthol in the presence of p-toluenesulphonic acid in water in good yields. These 2-aryl-5-methyl-2,3-dihydro-1H-3-pyrazolones were screened for in-vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv (MTB) using agar dilution method. Among the 15 compounds screened, 4-[(2,4-dichlorophenyl)(2-hydroxy-1-naphthyl)methyl]-2-(4-fluorophenyl)-5-methyl-2,3-dihydro-1H-3-pyrazolone displays the maximum potency with a minimum inhibitory concentration (MIC) of 1.6 μM against MTB, being 2.94 and 4.75 times more active than ciprofloxacin and ethambutol respectively.