Study On The Synthesis Of Benzothi (x) Azoles, Benzopyrones And1,3,4’-tricarbonyl Compounds

In this thesis, novel synthetic protocols for the preparation of benzothi(x)azoles, benzopyrones and1,3,4’-tricarbonyl compounds have been developed. The thesis includes the following four chapters:In the first chapter, a new method for the preparation of2-substituted benzoxazoles or their hybridswith pyrimidine nucleoside via RuCl3catalyzed oxidative condensation of2-aminophenol with aldehydesor5-formyl pyrimidine nucleoside by using ionic liquid as the reaction medium was developed.In the second chapter, novel synthetic approaches toward2-benzyl benzothi(x)azoles and2-benzoylbenzothi(x)azoles were developed. Specific studies are as follows:1. FeCl3·6H2O catalyzed, air oxidized tandem reaction of2-aminothiophenols and phenylacetaldehydes by using an ionic liquid as both reaction medium and co-catalyst was found to be an efficientnew protocol for the synthesis of2-benzyl benzothiazoles and2-benzoyl benzothiazoles.2. A novel method for the synthesis of2-benzyl benzothi(x)azoles and2-benzoyl benzothi(x)azolesthrough one-pot tandem reaction of1,1-dibromo-2-phenylethene with2-amino(thio)phenols promoted byTBAF·3H2O and RuCl3was developed.The third chapter is mainly about a copper (I) catalyzed tandem reaction of2-bromobenzoates with1,3-diketones. Depending on the structural characteristics of the1,3-diketone substrates, the tandemreaction can afford3,4-dihydro-2H-benzopyrones,2H-benzopyrones, or isocoumarins, respectively.In the fourth chapter, an efficient and environmentally benign procedure for the synthesis of1,3,4’-tricarbonyl compounds through TBAF·3H2O promoted, water mediated reaction of1,2-allenic ketoneand α-bromoketone or α-bromoacetate was developed. In addition, the usefulness of the1,3,4’-tricarbonylcompound as valuable synthetic intermediate was demonstrated by its efficient transformation into variousheterocyclic compounds.In summary, several novel synthetic methods for the preparation of benzothi(x)azoles, benzopyronederivatives and1,3,4’-tricarbonyl compounds have been developed in this thesis. With advantages such ashigh efficiency, easily obtainable starting materials, mild reaction conditions and inherent environmentallybenign nature, these methods are expected to find broad applications in synthetic organic chemistry andrelated areas.