Synthesis of some Bi- and polyheterocyclic compounds and investigation of their antimicrobial activities

In this study, heterocyclic carbamates, 41a-c, 42b, 43a-c ve 49 were synthesized starting from ester ethoxycarbonylhydrazones. The conversion of carbamate function into free amino group was carried out by acidic hydrolysis and compounds 46, 47 and 50 were obtained. The treatment of 46 and 50 with suitable aldehydes afforded the corresponding Schiff bases.The treatment of 3H-1,2,4-triazol-3-one (63) derivative that was obtained from the reaction of 2-[etoksi(4-klorobenzil)metilen]hidrazinkarboksilat (39b) with antipyrine, with ethyl bromoacetate and followed by hydrazine hydrate, produced the corresponding acetohydrazide (65), then, this compound was treated with phenyl- and benzylisothiocyanate at the same time with the treatment of nicotinic acid hydrazide (52) with 4-methylphenylisothiocyanate, separately, to obtain the corresponding carbothioamides (66a, 66b and 60). The basic treatment of all carbothioamide derivatives synthesized in this study caused to the conversion of carbothioamide side chain into 5-merkapto-1,3,4-triazole nucleus, thus compounds 53, 61, 67a and 67b formed, while the cyclization of the same carbothioamides in acidic media afforded 1,3,4-thiadiazole ring (62).The reaction of 57 and 65 with CS2 resulted in the formation of 1,3,4-oxadiazole derivatives (59 and 68). The Alkylation of 53 in basic media afforded the S-alkylated derivatives 54a and 54b, while the treatment of 53 with methyl piperazine in the presence of formaldehyde gave the corresponding Mannich base (55).The synthesis of Schiff bases 58a-f were performed by the reaction of 57 with several aldehydes. The reaction of 1,3,4-oxadiazole (68) with hydrazine hydrate produced, triazolotriazine compound (70). The condensation of 66a with 4-chloro and 4-nitrophenacyl bromide resulted the corresponding 1,3-thiazole derivatives (71a and 71b).The structures of the newly synthesized compounds were confirmed by IR, Mass, 1H and 13C NMR spectroscopic methods and elemental analyses and all compounds were screened for their antimicrobial activities. Some of them were found to possess good-moderate activities.