Synthesis of 2-(3-chloro-4-nitro-1-benzothien-2-yl)-1,3,4-oxadiazole-1,3,4-thiadiazole and 5-(3-chloro-4-nitro-1-benzothien-2-yl)-4H-1,2,4-triazole-3-thiol

In this paper the synthesis of some substituted 1,3,4-oxadiazole, 1,3,4-thiadiazole and 1,2,4-triazole is reported. 3-chloro-4-nitro-2-chloro Synthesis of 2-(3-chloro-4-nitro-1-benzothien-2-yl)-1,3,4-oxadiazole-1,3,4... 20 carbonyl benzo [b] thiophene(1) was synthesized from 2-nitrocinnamic acid by its reaction with thionyl chloride/dimethyl formamide in pyridine. Acid chloride(1) was converted to acid hydrazide(2) by its reaction with hydrazine hydrate in chloroform. The hydrazide (2) was treated with formic acid to give 3-chloro-4-nitro-2-[N-formyl acid hydrazide] benzo [b] thiophene (3), which was converted to substituted 1,3,4-oxadiazole and 1,3,4-thiadiazole (4,5) by its reaction with phosphorus pentoxide and phosphorus pentasulfide respectively. Treatment of acid hydrazide (2) with phenyl isothiocyanate gave substituted thiosemicabazide (6), which cyclized with sodium hydroxide solution to substituted 1,2,4-triazole (7). Compound (1) was treated with thiosemicarbzide in dry benzene to give substituted thiosemicarbazide (8), the substituted thiosemicarbazide (8) was cyclized with sodium hydroxide solution to give 5-substituted 1,2,4-triazole 3-thiol (9), alkylation of 1,2,4triazole (9) with propyl / butyl chloride in ethanol gave 5-(3-chloro-4-nitro-1-benzothien2-yl)-4H-1,2,4-triazole-3-propyl/butyl thiol (10,11) respectively. The structures of the synthesized compounds were confirmed by spectral and physical methods. INTRODUCTION Derivatives of 1,3,4-oxadiazole and 1,3,4-thiadiazole have been found to possess a wide spectrum of pharmacological, medical and biological activities. Moreover derivatives of 1,2,4-triazole are known to exhibit anti inflammatory, antiviral, analgesics antimicrobial anticonvulsant and antidepressant activities. Substituted 1,3,4-oxadiazoles were synthesized using various methods, acid hydrazides were treated with carbon disulfide in aqueous potassium hydroxide to gave substituted 1,3,4-oxadiazole as compounds (I,II).