Synthesis and Characterization of Novel Maleimide and Phthalimide Derivatives: TGA Study and Antibacterial Activity Evaluation

A series of N-substituted maleimide and N-substituted phthalimide derivatives compounds (A5–A8) were prepared by means of a two-step synthetic pathway. First, the intermediate amic acids (A1-A4) were formed via ring-opening reactions of maleic anhydride and phthalic anhydride with primary amines, including 3,5-dimethoxyaniline and 2-amino-5-bromopyridine, in acetone at room temperature. In the second step, intermediate acids undergo ring-closure cyclization with anhydrous sodium acetate and acetic anhydride in thermal sublimation conditions for 4 h to afford final compounds in good yields. FT-IR,1H-NMR and 13C-NMR spectroscopy techniques were used to characterize the chemical structures of both intermediate and the final prepared compounds. The thermal stability of compounds A5 and A8 was studied by thermogravimetric analysis (TGA) under an inert argon atmosphere. The analysis of thermal curves indicated several stages of weight loss, correlated with the breakdown various functional groups in the structural framework and indicating excellent thermal stability of these compounds at high temperatures. Activity of compounds A5-A8 were assessed against two bacterial isolates (Gram-positive-Staphylococcus aureus , and Gram-negative-E.coli) by the diffusion method at 100%, 50%, and 25% concentrations. Results: Compared to the standard antibiotic gentamicin, the results displayed good repression of bacterial growth.