Nano zinc oxide-Catalyzed Synthesis ofSubstituted benzoxazoles, benzimidazoles and benzothiazoles viaCondensation of ۲-substituted anilines withnitriles

Zinc oxide (ZnO) has attracted considerable attentions and is recognized as one of the mostpromising semiconductor materials in electronic and photonic applications [۱] and ZnOnanoparticles are very efficient in impart of antibacterial effect to fabric [۲]. On the otherhand, Benzoxazoles, benzimidazoles and benzothiazoles are important class of compoundsand have exhibited a variety of pharmacological and biological activities such as melatoninreceptor agonist, anticancer, anti microbacterial, elastase inhibitory, photochromic agents andlaser dyes [۳]. There are several known strategies for the synthesis of these heterocycliccompounds includes: coupling of Carboxylic acids, acid chlorides, nitriles, aldeydes andorthoesters with ۲-substituted anilines, Beckmann rearrangement of ۲-acylphenol oximes andphotocyclization of phenolic Schiff bases [۴]. These methods often need long reaction timesand harsh conditions. These condensations usually are carried out by thermal fusion, heatingin solvents or in various concentrations of hydrochloric, sulfuric acid or polyphosphoric acid,or by heating under pressure in the presence of dilute hydrochloric acid. So, introduce of anew method for this conversion is necessary. In continuation of our interest in thedevelopment of synthetic methods for the preparation of heterocyclic compounds we havefocused our attention to the preparation of benzoxazoles, benzimidazoles and benzothiazolesby reaction between ۲-substituted anilines and nitriles in the presence of nano zinc oxide asefficient basic catalyst (Scheme ۱).