Green synthesis of UV absorber (E)-2-(((4-(benzyloxy)phenyl)imino)methyl)phenol by microwave method

Abstract

In this work, a UV absorber compound (E)-2-(((4-(benzyloxy)phenyl)imino)methyl)phenol was synthesized by microwave method using a two steps protocol. In the first step, α-(4-hydroxyphenylimino)-o-cresol (1) was synthesized from 4-aminophenol and salicylaldehyde by circulating under microwave heating at 60 oC for 8 minutes, the reaction yield reached 82.91 %. In the second step (E)-2-(((4-(benzyloxy)phenyl)imino)methyl)phenol (2) was synthesized from precursor (1) and benzyl bromide by circulating under microwave heating at 80 oC for 3 minutes, the reaction yield reached 25.08 %. The overall yield for the synthesis of UV absorber 2 was 20.79 %. The molecular structures of precursor (1) and product (2) were analysed by high performance liquid chromatography - mass spectrometry (LC/MS) and nuclear magnetic resonance (NMR) methods. The UV absorbance of precursor (1) and product (2) was investigated by UV absorption spectrometry. The obtained results show that product (2) has a higher UV absorption intensity than precursor (1), the UV absorption region extends from 240 nm to 390 nm, the maximum absorption peak is at the wavelength (λmax) of 350 nm. The UV absorber (E)-2-(((4-(benzyloxy)phenyl)imino)methyl)phenol with cyclic structure, low molecular weight, and high UV absorbance has potential application as an UV absorber for greenhouse covering plastic, paint and ink systems.