Novel Synthesis and Antimicrobial Activity of 3‐Substituted 5‐bromo‐7‐methyl‐1,2,4‐triazolo‐[3,4‐b]‐benzothiazoles

Abstract

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.

Importance of Fluorine in Benzazole Compounds

“…Moreover, the benzothiazole core is a widespread scaffold that has been extensively studied [ 54 , 55 , 56 , 57 , 58 , 59 ] and many derivatives are found to be antimicrobial [ 49 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 ], anticancer [ 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 ], anti-Alzheimer’s [ 92 , 93 ], anti-inflammatory [ 94 , 95 , 96 ], anti-HIV [ 97 , 98 , 99 ] anticonvulsant [ 100 , 101 , 102 ], antioxidant [ 39 , 103 ], anti-tuberculosis [ 104 ...…”

Copper-Coordinated Thiazoles and Benzothiazoles: A Perfect Alliance in the Search for Compounds with Antibacterial and Antifungal Activity

“…The study of antifungal activity showed inhibition zones of 1.6 and 1.4 mm against A. niger and A. flavus, respectively. Nonetheless, the free ligand showed antimicrobial activity only in B. subtilis, with an inhibition halo of 1.1 mm [141] (Figures 13 and 14). Copper complexes with bidentate benzothiazole ligands functionalized with hydrazine moieties.…”

Oxidative Cyclization of 4‐(2‐Mercaptophenyl)‐Substituted 4H‐1,2,4‐Triazolium Species to Tricyclic Benzothiazolium Salts

“…Among these molecules are several fused nitrogen‐ and sulfur‐containing heterocyclic anti‐cancer agents incorporating a (benzo)thiazole fragment, [10–22] a thiadiazole ring, [23–28] or a thiadiazine unit [27–29] . The same scaffolds can be found in molecules with antibacterial, antimicrobial and antifungal properties, [22,30–35] prospective therapeutic agents used to treat asthma or chronic obstructive pulmonary disease, [36–38] molecules with anti‐inflammatory activity, [39] compounds with antidiabetic activity, [40,41] and promising therapeutics to treat Alzheimer's disease [42–44] or schizophrenia [45] …”