Synthesis of new 1-(9-ethylcarbazol-3-yl)-5-oxopyrrolidine-3-carbohydrazide derivatives /

In this work, 1-(9-ethylcarbazol-3-yl)-5-oxopyrrolidine-3-carbohydrazide 1 was used as a precursor for the synthesis of 5-oxopyrrolidine derivatives containing fragments of hydrazone, pyrrole, triazolethione, 1,2,4- triazine, and pyrrolidinone. In the first stage of this study a series of heterocyclic compounds was prepared. For 1,3,4-oxadiazole 2, hydrazide 1 was treated with carbon disulphide in alkaline methanolic solution. The reaction proceeded via an intermediate hydrazinocarbothioate whose aqueous solution was acidified with hydrochloric acid to pH 1 to obtain the target compound 2. The condensation of hydrazide 1 with hexane-2,5-dione in propan-2-ol in the presence of a catalytic amount of acetic acid gave 2,5-dimethylpyrrole 3. To obtain 4-phenyl-1,2,4-triazole 5, thiosemicarbazide 4 was first synthesized by refluxing hydrazide 1 with phenylisothiocyanate in the mixture of methanol and 1,4-dioxane for 7 h. The conversion of tiosemicarbazide 4 to triazole 5 was carried out in refluxing aqueous 2 KOH solution with the subsequent acidification of the reaction mixture with hydrochloric acid to pH 2. [.].