Synthesis of Thiazole Derivatives as Antimicrobial Agents by Green Chemistry Techniques

Abstract

Amine (2) and (26) was obtained from the condensation of the corresponding amines with 3,4-difluoronitrobenzene. The reduction of nitro group produced the corresponding amines (3 and 27). The synthesis of esters (7, 12, 19, 28) was carried out from the treatment of the amines, 1, 3, 18, 27 with ethylbromoacetate, then these compounds were converted to the corresponding hydrazides (8, 13, 29) by the treatment with hydrazine hydrate. Triazole was obtained from the intramolecular cyclisation of the corresponding carbothioamide in basic media and this compound wad then converted to the morpholine-triazole-penicillin hybrid by a mannich reaction. The cyclocondensation of hydrazine carbothioamides (9b, 14, 21) or urea (4) with 2-bromo-1-(4-chlorophenyl) ethenone generated thiazole derivatives. On the other hand, the treatment of 4, 9b and 14 with ethyl bromoacetate yielded 4-oxo-1,3-thiazolidines (6, 11, 16). Three methods containing conventional, microwave and ultrasound mediated techniques were applied. Best results were assessed using microwave and ultrasounds promoted procedures. All the newly synthesized compounds were characterized on the basis of spectroscopic techniques, and they were screened for their antimicrobial activity. Some of them exhibited good-moderate activity on the test bacteria.