Methodological Study And Synthesis Of Nitrogen-containing Heterocyclic Compounds

Nitrogen-containing heterocyclic compounds are widely found in many natural products and have a wide range of pharmacological and physiological activities.In addition,the heterocycles have comprehensive applications in medicine and pesticide fields,industry and multi-functional materials.Given the special nature and structure of heterocyclic compounds,the construction of diverse heterocycles has emerged as hot topic in organic synthetic chemistry.Based on previous reports,this dissertation focuses on the development of simple and efficient methods for the construction of nitrogen-containing heterocyclic skeletons,such as 1,2,3-triazoles,triazines,isothiazoles,thiazoles and so on.This dissertation is divided into the following four chapters:The first chapter mainly reviews the research progress for the synthesis of 1,2,3-triazoles,triazines,isothiazoles and thiazoles in recent years.The second chapter focuses on the synthesis of 1,2,3-triazoles via a Cu-catalyzed oxidative interrupted click reaction with arylboronic acids,terminal alkynes and azides at room temperature.In the presence of oxygen,the click reaction was interrupted by arylboronic acid to provide a range of substituted C-5 arylated 1,2,3-triazoles in decent yields.This current method features high efficiency,mild conditions,readily available starting materials,simple operation(in open test tube)and high regioselectivity.The third chapter describes the synthesis of a series of symmetric and asymmetric triazine compounds with amidines and halogenated difluoroalkylating reagents under basic conditions.In this paper,halogenated difluoroalkylating reagents could serve as an unique C1 source via quadruple cleavage under the transition-metal free and oxidant-free conditions,in which multiple C-N bonds were constructed in one-pot to access the triazines.The fourth chapter discusses the divergent synthesis of 3-substituted isothiazoles and thiazoles with enamines,sulfur powder and halogenated difluoroalkylation reagents.In this cascade reaction,cheap and widely accessible sulfur powder was used as S source and halodifluoroalkylating reagent was used as C-COOEt donor via triple cleavage by breaking one C-X bond as well as two C-F bonds.The current method provides a mild route for the assembly of isothiazoles and thiazoles,which are prevalent scaffolds in nature products and bioactive molecules.