Synthesis of Thiazole Derivatives as Antimicrobial Agents by Green Chemistry Techniques

Abstract

Amines (2) and (26) were obtained from the condensation of the correspondingamines with 3,4-difluoronitrobenzene. The reduction of nitro group produced the correspondingamines (3 and 27). The synthesis of esters (7, 12, 19, 28) was carried out from the treatmentof the amines, (1, 3, 18, 27) with ethyl bromoacetate, then these compounds were convertedto the corresponding hydrazides (8, 13, 29) by the treatment with hydrazine hydrate. Thetriazole was obtained from the intramolecular cyclisation of the corresponding carbothioamidein basic media and this compound was then converted to the morpholine-triazole-penicillin hybridby a mannich reaction. The cyclocondensation of hydrazine carbothioamides (9b, 14, 21) orurea (4) with 2-bromo-1-(4-chlorophenyl)ethenone generated the thiazole derivatives. On theother 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 ultrasoundmediatedtechniques were applied. Best results were assessed using microwave- and ultrasoundpromotedprocedures. The structures of the newly synthesised compounds were elucidated byspectroscopic techniques, and the antimicrobial activity screening studies were also performed.Some of them exhibited good to moderate activity on the test bacteria.