Microwave assisted synthesis, photoisomerization study and antioxidant activity of a series of N-acylhydrazones

Abstract

A series of N-acylhydrazone 4(a-f) were prepared by condensation of 2-hydroxybenzohydrazide with substituted benzaldehyde derivatives and catalytic amount of acetic acid via a simple method using microwave-assisted synthesis. Reaction conditions such as temperature (60 °C), irradiation power (150 w), and catalyst were optimized. Target compounds were obtained in prompt time (4–10 min) and with excellent yields reaching 98 %. Structural characterization was accomplished using FTIR, 1H NMR, 13C NMR and EIS-MS spectrometry. Reversible light-induced E/Z isomerization at the C = N bond of the synthetized compounds was achieved as function of time in two solvents: dimethylsulfoxide (DMSO) and methanol. The photodynamical E/Z conversion revealed the influence of the solvent on this process that took about 30 min in methanol and 45 min in DMSO. Moreover, antioxidant activity was evaluated for all the synthetized N-acylhydrazones using the 2,2 Dipheny-1-picrylhydrazyl (DPPH) assays. Results showed promising antioxidant effects for compounds 2-hydroxy-N′-(2-hydroxy-4-(p-tolyldiazenyl)benzylidene)benzohydrazide (4e) and 2-hydroxy-N′-(2-hydroxy-3-methoxy-4-(p-tolyldiazenyl)benzylidene)benzohydrazide (4f) that are combining both the acylhydrazone function and an azo fragment in their structures.

Keywords

• Acylhydrazone
• Microwave irradiation
• Photoisomerization
• UV–Visible
• Antioxidant activity