Convenient syntheses of 5‐[(2‐methyl‐5‐nitro‐1H‐imidazol‐1‐yl)methyl]‐1,3,4‐oxadiazole‐2(3H)thione and N‐substituted 2‐amino‐5‐[(2‐methyl‐5‐nitro‐1H‐imidazol‐1‐yl)methyl]‐1,3,4‐thiadiazoles

Oxidation of metronidazole (4) with sodium dichromate yielded the corresponding 2-(2-methyl-5-nitro-1H-imidazol-1-yl)acetic acid (5) which was esterified with 1-butanol to give butyl 2-(2-methyl-5-nitro-1H-imidazol-1-yl)acetate (8). Reaction of the latter with hydrazine hydrate gave 2-(2-methyl-5-nitro-1H-imidazol-1-yl)acetohydrazide (9). Compound 5-[(2-methyl-5-nitro-1H-imidazol-1-yl)methyl]-1,3,4-oxa-diazole-2(3H)-thione (10) could be obtained through the reaction of compound 9 with carbon disulfide in basic medium. Subsequent alkylation of compound 10 afforded alkyl 2-(5-[(2-methyl-5-nitro-1H-imidazol-1-yl)methyl]-1,3,4-oxadiazol-2-ylthio)acetate (11) in good yield. Reaction of hydrazide 9 with substituted isothiocynate yielded 1-[2-(2-methyl-5-nitro-1H-imidazol-1-yl)acetyl]-4-aryl(or ethyl)thiosemicarbazide (12) which was cyclized in acidic media to N-substituted 2-amino-5-[(2-methyl-5-nitro-1H-imidazol-1-yl)methyl]-1,3,4-thiadiazole (13).