Synthesis of some heterocyclic compounds containing quinoline ring and investigation of their antimicrobial activities

In the present study, first of all, quinolin-2-carbohydrazide (65) was obtained from the reaction of quinaldic acid ethyl ester that was obtained starting from quinaldic acid, with hydrazine hydrate. Then it was converted to the corresponding carbothioamide or carboxamide derivatives by the treatment with benzylisothiocyanate or benzylisocyanate, respectively. The treatment of these intermediates with sodium hydroxide produced 4-benzyl-5-(quinolin-2-yl)-4H-1,2,4-triazole-3-thiol (67) and 4-benzyl-5-(quinolin-2-yl)-2,4-dihydro-3H-1,2,4-triazole-3-one (69) compounds. 5-(quinolin-2-yl)-1,3,4-oxadiazole-2-thiol (74) was prepared from the reaction of compound 65 with carbon disulfide in basic media.In the second step of the study, compounds 67, 69 and 74 was converted Mannich bases containing one of morpholine, piperazine or piperidine.The treatment of quinaldic acid with thiocarbohydrazide yielded 4-amino-5-(quinolin-2-yl)-4H-1,2,4-triazole-3-thiol (77), while the reaction of the same ped in the precursor with thiosemicarbazide resulted in the formation of 5-(quinolin-2-yl)-1,3,4-thiadiazol-2(H)-imine (78).The structures of the obtained compounds were confirmed on the basis of spectroscopic methods. The antimicrobial activities were screened by Şengül Alpay Karaoğlu (Rize University Department of Biology).