4-Hydroxy-3-methoxy-benzaldehyde series aroyl hydrazones: synthesis, thermostability and antimicrobial activities

Abstract

Efficient synthetic procedures for the preparation of aroyl hydrazones were developed by converting the corresponding ethyl ester into hydrazides, followed by a reaction with 4-hydroxy-3-methoxy-benzaldehyde. A series of aromatic hydrazides and aroyl hydrazones were characterized by elemental analysis, IR, ¹H NMR, ¹³C NMR and thermogravimetric analysis. The thermal gravity analysis showed that the compounds 3a–3d were stable below 228.23, 227.65, 118.97 and 179.51 °C, respectively. The aromatic hydrazides and aroyl hydrazones showed antimicrobial activity towards Staplylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The antibacterial activity experiments indicated that aroyl hydrazones had higher activity than the hydrazides. The presence of a hydroxyl group, as well as the number and position of the hydroxyl groups, were important and further enhance the antimicrobial activity.