Synthesis of Benzazolyl - azastilbenes and Their Fluorescence Spectra

Abstract

Benzoxazolyl- and benzothiazolyl-azastilbene derivatives were synthesized in high yield by the cendensation of diethyl benzazolylpicolylphosphonates with aromatic aldehydes in the pres ence of sodium methoxide in dimethylformamide.
The phcsphonates were prepared by the reaction of the bromomethylbenzazolylpyridiRes and triethyl phosphite at 160eC for 5 minutes under a nitrogen atmosphere.
Absorption aRd fluorescence spectra of these aza-stilbenes: were measured in dimethylfolmalnide. The. fluoresgence unintensities of 4-(2-benzoxazolyl)-3-azastilbenes are eonsiderably stronger than those Qf 4-(2-benzQxazolyl)-2-azastilbenes, theugh the wavelength of abserptioh and fluorescence maxima and the absorption intensities are comparable. The absorption and fluorescence maxima of benzothiazolyl-3-azastilbenes are shifted to longer wavelength by 5tvlO nm compared with those of the corresponding benzoxazole derivatives, but the fuorescence intensities of the former are weak.