Novel Synthesis and Heterocyclization of Thiosemicarbazide and Cyclic Heterodienes derivative

Abstract

Addition of hydrazine to one equivalent of benzoylisothiocyanate furnished thiosemicarbazide 2 . The hydrazine derivative 2 was condensed with benzaldhyde to produce thiosemicarbazon derivative 3. Upon treatment, the Schiff base 3 with bromine/ acetic acid afforded thiadiazole derivative 4. Cyclocondensation of thiosemicarbazide 2 and cyclohexanone yielded benzopyrazole derivative 8. Benzopyrazole derivative 8 undergo Michael addition to polarized double bond of maleicunhydride producing poly heterocyclic compound via the formation of nonisolable adduct 9. Sodium hydroxide was reacted with two equivalents of benzylisothiocyanate 2 to form thiosemicarbazide of type 12 that cyclized to the thiadiazole derivative 13 . Upon keeping thiadiazole derivative 13 and polarized ene of benzylidenemalononitrile undergo [4+2] cycloaddition producing diazine 17a. Also, benzyldiene ethyl cyanoacetate reacted with heterocyclicdiene 13 to furnish diazine of type 17b . Upon treatment of compound 13 with I2 in acetic acid resulted in oxidation affording the oxidized product 18. Oxidation of compound 13 using H2O2 in acetic acid resulted in ring opening followed by oxidation producing semicarbazide 19. Thiadiazole derivative 13 undergo bromination in acetic acid to provide S,S-dibromo and N-bromo derivative 20, 21