Studies Of Nucleophilic Substitution Reaction, Nucleophilic Addition Reaction And Multi-Component Reaction Catalyzed By N-Heterocyclic Carbenes

N-heterocyclic carbenes,as a kind of versatile organocatalysts,reverse the polarity of aldehydes,resulting umpolung aldehydes,or acyl anion equivalents.The umpolung aldehydes are induced to undergo various nucleophilic reactions.According to the types of reactions catalyzed by N-heterocyclic carbenes,this dissertation consists of four chapters.Chapter 1:The history of the development of N-heterocyclic carbenes was reviewed. Benzoin condensation,Stetter reaction and a~3 to d~3 umpolung,as three kinds of classical reactions catalyzed by N-heterocyclic carbenes were presented.These reactions provide a concise and effective method for construction of carbon-carbon bonds and various functionalized compounds.Chapter 2:The nucleophilic substitution reactions catalyzed by N-heterocyclic carbenes was briefly reviewed,and a novel intramolecular nucleophilic substitution reaction catalyzed by N-heterocyclic carbenes was presented,which was a more direct and efficient way to construct skeletons of benzopyrones and benzofuranones.Chapter 3:The intramolecular nucleophilic addition reaction of acyl anion equivalents to enol ethers was described.By combining our previous work,the precise mechanistic study on the formation of benzofuranones has been further investigated.Chapter 4:N-heterocyclic carbenes-triggered multicomponent reactions were briefly reviewed,and a simple method of a self-assembly of functionalizedα-hydroxy carbonyl compounds from various aldehydes and allylic acetates was presented,which was mediated by an unprecedented combination of N-heterocyclic carbenes and palladium catalysis.