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Syntheses of substituted 1-methyl-2-(1,3,4-thiadiazol-2-yl)-4-nitropyrroles and 1-methyl-2-(1,3,4-oxadiazol-2-yl)-4-nitropyrroles

1995; Wiley; Volume: 32; Issue: 1 Linguagem: Inglês

10.1002/jhet.5570320121

1943-5193

Faranak Firoozi, K. Javidnia, Maryam Kamali, Atoosa Fooladi, Alireza Foroumadi, Abbas Shafiee,

Synthesis and Biological Evaluation

Abstract Starting from readily available ethyl‐4‐nitropyrrole‐2‐carboxylate ( 1 ), substituted 1‐methyl‐2‐(1,3,4‐thiadiazol‐2‐yl)‐4‐nitropyrroles and 1‐methyl‐2‐(1,3,4‐oxadiazol‐2‐yl)‐4‐nitropyrroles were prepared. The reaction of 1 with diazomethane gave ethyl 1‐methyl‐4‐nitropyrrole‐2‐carboxylate ( 2 ). Reaction of compound 2 with hydrazine hydrate afforded the corresponding hydrazide 3 . The reaction of 3 with formic acid yielded 1‐(1‐methyl‐4‐nitropyrrole‐2‐carboxyl)‐2‐(formyl)hydrazine ( 7 ). Refluxing of the latter with phosphorus pentasulfide in xylene yielded compound 6 in 40% yield. Reaction of compound 7 with phosphorus pentoxide afforded compound 9 . Reaction of compound 3 with 1,1′‐carboxyldiimidazole in the presence of triethylamine yielded 2‐(1‐methyl‐4‐nitro‐2‐pyrrolyl)‐1,3,4‐oxadiazoline‐4( H )‐5‐one ( 11 ). Refluxing compound 3 with cyanogen bromide in methanol gave compound 12 . Compound 13 could be obtained through the reaction of compound 3 with carbon disulfide in basic medium. Alkylation of compound 13 afforded the correspanding alkylthio derivative 14 . Reaction of 1‐methyl‐4‐nitropyrrole‐2‐carboxylic acid ( 15 ) with thiosemicarbazide and phosphorus oxychloride gave 2‐amino‐5‐(1‐methyl‐4‐nitro‐2‐pyrrolyl)‐1,3,4‐thiadiazole ( 16 ). Sandmeyer reaction of compound 16 yielded 2‐chloro‐5‐(1‐methyl‐4‐nitro‐2‐pyrrolyl)‐1,3,4‐thiadiazole ( 17 ). Refluxing of the latter with thiourea afforded 2‐(1‐methyl‐4‐nitro‐2‐pyrrolyl)‐1,3,4‐thiadiazoline‐4( H )‐5‐thione ( 18 ). Alkylation of compound 18 gave the corresponding alkylthio derivative 19 . Oxidation of the latter with hydrogen peroxide in acetic acid yielded 2‐(1‐methyl‐4‐nitro‐2‐pyrrolyl)‐5‐methylsulfonyl‐1,3,4‐thiadiazole ( 20 ).