4‐Methyl acetanilide (1) on treatment with bromine in acetic acid, followed by hydrolysis with dilute HCl/NaOH solution, yielded 2‐bromo‐4‐methyl aniline (2), which on treatment with sodium thiocyanate in acetic acid afforded 2‐amino‐4‐bromo‐6‐methyl benzothiazole (3). Compound 3 in ethylene glycol was heated at 150°C with 80% hydrazine hydrate to get 4‐bromo‐2‐hydrazino‐6‐methyl benzothiazole (4). This hydrazino compound 4 on heating with formic acid for 3 h yielded 4‐bromo‐2‐hydrazinoformyl‐6‐methyl benzothiazole (5). Same compound 4 when heated independently with formic acid for 6 h/urea for 3 h/carbon disulfide in alkali afforded 5‐bromo‐7‐methyl (6)/5‐bromo‐3‐hydroxy‐7‐methyl (7)/5‐bromo‐3‐mercapto‐7‐methyl (8)‐1,2,4‐triazolo‐[3,4‐b]‐benzothiazoles, respectively. Compound 4 on heating with acetic acid/acetic anhydride gave acetyl benzothiazolyl derivative 9, which on cyclization with orthophosphoric acid yielded 5‐bromo‐3,7‐dimethyl‐1,2,4‐triazolo‐[3,4‐b]‐benzothiazole (10). All these newly synthesized compounds were screened for antimicrobial activity against Escherichia coli (Gram −ve), Bacillus subtilis (Gram +ve), Erwinia carotovora, and Xanthomonas citri using ampicillin, streptomycin, and penicillin as a standard for comparison.

All new compounds (VI), (VIII), (X) and (XIII) are tested for their antimicrobial activities.