Synthesis and antibacterial screening of hydrazones, Schiff and Mannich bases of isatin derivatives

Schiff bases and hydrazones of substituted isatins (1-28), were prepared by reacting isatin and aromatic primary amines/hydrazines. A new series of the corresponding N-Mannich base (29-35) was synthesised by reacting them with formaldehyde and diphenyl amine. The chemical structures were confirmed by means of H-1-NMR, IR spectral data and elemental analysis. The compounds were screened for antibacterial activity against seven Gram (+) and seven Gram (-) standard and pathological bacterial strains by the paper disc diffusion technique. The minimum inhibitory concentrations of the active compounds were determined. 1-Diphenyl amino-methyl-3-(4-bromo phenylimino)-1,3-dihydro-indol-3-one (30) and 3-(4-bromo phenylimino)-5-nitro-1,3-dihydroindol-3-one (13) were found to be the most actives compounds of the series. Mannich bases exhibited higher activity than the corresponding Schiff bases. (C) 2001 Editions scientifiques et medicales Elsevier SAS.