Synthesis and Biological Evaluation of Some Heterocyclic Compounds from Salicylic Acid Hydrazide[1]

摘要

Different heterocyclic compounds were prepared starting from 2-hydroxy benzohydrazide; for example, cyclization of hydrazide hydrazone 3 derived from 2-hydroxybenzohydrazide 2 with acetic anhydride or concentrated sulfuric acid gave 1,3,4-oxadiazole derivatives 4-5. On the other hand, direct cyclization of 2-hydroxy benzohydrazide 2 with one carbon cyclizing agent gave a new derivative of 1,3,4-oxadiazole 7-11. Heating of hydrazide hydrazone 3 with thioglycolic acid in pyridine gave thiazolidinone 12. When 2-hydroxy benzohydrazide 2 reacted with aliphatic carboxylic acids such as formic acid or acetic acid, it gave the corresponding N-formyl or N-acetyl derivatives 6. Subsequent cyclization of 6 using phosphorous pentasulphide in pyridine gave 1,3,4-thiadiazoles 13. Cyclization of 2-hydroxy benzohydrazide with ethyl acetoacetate gives pyrazolone derivative 14. Finally, when an ethanolic solution of acid hydrazide 2 was treated with ammonium thiocyanate in 35% HCl, it gave the thiosemicarbazide 15. Subsequent treatment of 15 with concentrated sulfuric acid or 10% sodium hydroxide gave 5-amino-1,3,4-thiadiazole 16 and 1,2,4-triazole 17, respectively. The structures of all newly isolated compounds were confirmed using H-1 NMR, IR spectra, and elemental analyses. The antimicrobial activities for all isolated compounds were examined against different microorganisms.