Trabalho

2-(2-(1H-benzo[d]imidazol-1-yl) acetyl)-N-aryl hydrazinecarbothioamide 2a-c General procedure To a mixture of the acetohydrazide 1 (1.9 g, 10 mmole) in absolute ethanol (50 ml)arylisothiocyanate (10 mmol), was added, and the reaction mixture was heated under reflux for 6 h (follow by TLC), then left to cool. The separated solid was collected by filtration, washed with ethanol and finally crystallized from ethanol to afford thiosemicarbazide 2a-c
General procedure for the synthesis of 1,3,4-thiadiazole 3a-c Each thiosemicarbazide 2a-c (10 mmol) was added portion wise to 10 ml of conc. sulfuric acid with continuous stirring. The reaction mixture was stirred further for 4 h at room temperature. The reaction mixture was slowly poured into crushed ice with stirring and neutralized with ammonia. The mixture was allowed to stand overnight and the solid separated out was filtered and washed with cold water. The solid was dried and crystallized from a mixture of DMF and water (1:1) to furnish di‐substituted 1,3,4‐thiadiazole 3a-c
General procedure for the synthesis of 1,3,4-oxadiazol-2-amine 4a-c To a suspension of the thiosemicarbazides 2a-c (10 mmol) in ethanol 100 ml, (4N, sodium hydroxide solution) 10 ml was added with shaking. A solution of iodine and potassium iodide was added dropwise with stirring till the color of iodine persisted. The mixture was stirred for 5 h, then left to cool. The separated solid was filtered off, washed with water and crystallized from EtOH to give 4a-c.
General procedure for the synthesis of 1,2,4-triazole-3-thiol 5a-c To a suspension of the thiosemicarbazides 2a-c (10 mmol) in ethanol(15ml), 10ml of 2 N NaOH was added. The mixture was refluxed for 4 h, then left to cool. The reaction mixture was acidified with concentrated hydrochloric acid .The separated solid was filtered off, washed with water and crystallized from ethanol General procedure of Preparation of compounds 6-17. To a solution of 5a-c of (10 mmol) and 0.4 g NaOH