Synthesis and Antitumor Activity Evaluation of Some Novel‐Fused and Spiro Heterocycles Derived from a 2(3H)‐Furanone Derivative

2(3H)‐furanone 1 was fused with methyl‐4‐aminobenzoate followed by hydrazinolysis to give the acid hydrazide derivative 3. Treatment of 3 with carbon disulfide gave 4‐amino‐5‐mercapto‐3‐substituted triazole derivative 5. The presence of mercapto and amino groups adjacent to each other in compound 5 made it valuable key precursor for the formation of fused and spiro heterocycles. Ring transformation of 5 into triazolothiadiazole and triazolothiadiazine derivatives is investigated. The antitumor and antimicrobial activities of the synthesized compounds were evaluated. Some of the tested compounds showed promising activities.