Synthesis and antimicrobial activity of novel pyrazole, pyrazoline, pyrazolinone and pyrazolidinedione derivatives of benzimidazole.

Four novel series of pyrazolylbenzimidazole derivatives have been prepared, namely 2-[(1-substituted phenyl-3,5-dimethyl-4-pyrazolyl)methyl]benzimidazole 5a-d 2-[(1-substituted phenyl-3-methyl-5-oxo-4,5-dihydro-4-pyrazolyl-4-yl)methyl]benzimidazoles 6a-d; 2-[(1-substituted phenyl-3,5-dioxopyrazolidin-4-yl)methyl]benzimidazoles 7a-d and 2-[(4-(1-phenyl-5-aryl-4,5-dihydro-3-pyrazolyl)phenylaminoacetyl]thio- methyl)-benzimidazoles 12a-e. The antimicrobial testing of the prepared compounds was performed using Escherichia Coli (NCTC 5933) as Gram-negative bacteria, Staphylococcus aureus (NCTC 4163) as gram-positive bacteria and Candida albicans (NCTC 5310) as yeast like fungi. The most potent compound was the pyrazolone 6a which exhibits interesting antibacterial activity against the gram-negative bacteria E. coli.