When malono hydrazide 1 was allowed to react with benzaldehyde; the reaction yielded spiro compound 2. The reaction may start via formation of condensed product 2; followed by the addition of activated methylene to activated C=N. Also, condensation of the target 1 with cyclopentanone produced the non-isolable Schiff product 4 that underwent intramolecular cycloaddition reaction to form the spiro product 5. The addition of nucleophilic NH2 group of target 1 to heteroallene in basic medium resulted in triazole heterocyclization. The reaction may proceed via the formation of non-isolable thiosemicarbazide derivative 6; followed by intramolecular cyclization to furnish triazole derivative 7.
Pyrazole derivative 8 underwent Michael addition with heteroallene providing fused triazole derivative 10 which may be formed through the non-isolable thiourea derivative. The target 8 underwent cycloaddition reaction with carbon disulphide to produce fused thiadiazole 12. Compound 8 underwent double nitrozation when treated with NaNO2/acetic acid yielding nitroso derivative 13.