Synthesis of formazans from Mannich base of 5-(4-chlorophenyl amino)-2-mercapto-1,3,4-thiadiazole as antimicrobial agents

Abstract

5-(4-Chlorophenyl amino)-2-mercapto-1,3,4-thiadiazole (I) was refluxed with formaldehyde and ammonium chloride in ethanol yielding the Mannich base 5-(4-chloro phenyl amino)-3-aminomethyl-2-mercapto-1,3,4-thiadiazole (II). Esterification with 4-chloro-(2,6-dinitro phenoxy)-ethyl acetate (III) under anhydrous conditions gave the intermediate (IV). Subsequent hydrazinolysis with hydrazine hydrate gave the corresponding hydrazide 3-amino methyl-5-(4-chloro phenyl amino)-2-mercapto-4′-(2′,6′-dinitro phenoxy)-acetyl hydrazide (V). The hydrazide was converted into the Schiff bases (VIa–b) by reacting with 2-chlorobenzaldehyde and 3-methoxy-4-hydroxy benzaldehyde in presence of methanol containing 2–3 drops of acetic acid. Diazotisation with aromatic amines, sulphanilic acid and sulphur drugs gave the formazans (VIIa–g) respectively. Chemical structures have been established by elemental analysis and the spectral techniques of FTIR, 1H NMR and mass. Antimicrobial activity (in vitro) was evaluated against the two pathogenic bacterial strains. Escherichia coli and Salmonella typhi, three fungal strains Aspergillus niger, Penicillium species and Candida albicans. The compounds have shown moderate activity.

Keywords

• Mannich base
• 1,3,4-Thiadiazole
• Formazans
• Antimicrobial