Studies On The Synthesis Of Benzothiazoles, Benzoxazoles And Polysubstituted Benzenes

In this thesis, novel synthetic methods for the preparation of2-aminobenzothiazoles,2-aminobenzoxazoles, polysubstituted benzenes and α,β-unsaturated nitrile have been developed. It mainlyincludes the following two chapters:In the first chapter, an environmentally benign, efficient and practical route for the preparation of2-aminobenzothiazoles and2-aminobenzoxazoles was developed. Specific studies are as follows:1. Tandem reactions of isothiocyanates with2-aminothiophenols were found to proceed rapidly andefficiently in water. Through these reactions, a series of2-aminobenzothiazoles were synthesized with goodyields.2. FeCl3·6H2O catalyzed tandem reaction of isothiocyanates with2-aminophenols were studied byusing water as the rection medium. Through this reaction, a series of2-aminobenzoxazoles were obtainedsmoothly.In the second chapter, novel procedures for the preparation of polysubstituted benzenes andα,β-unsaturated nitriles were successfully developed. Specific studies are as follows:1. Base catalyzed tandem reaction of1,2-allenic ketones with cyanoacetate was found to be a noveland efficient approach toward polysubstituted benzenes. By using this protocol, a series of highlyfunctionalized benzenes were prepared efficiently and conveniently.2. Base catalyzed tandem reaction of1,2-allenic ketones with2-substituted cyanoacetates was found tobe a reliable pathway toward α,β-unsaturated nitriles. Through this reaction, a series of α,β-unsaturatednitriles with different substitution patterns were conveniently obtained.In summary, this thesis demonstrates several facile and efficient procedures for the synthesis of2-aminobenzothiazoles,2-aminobenzoxazoles, multisubstituted benzenes and α,β-unsaturated nitriles.These novel protocols employ readily available starting materials and show high efficiency, eco-friendlynature and good functional group tolerance.