Copper-catalyzed Cascade Cyclization Reaction Of Enamines And Electron-deficient Terminal Alkynes

Alkynes is an extremely important intermediate in organic synthesis.Various reactions involving alkynes,such as coupling reactions,cyclization reactions,are important ways to prepare various important organic compounds.Transition-metal-catalyzed cyclization of alkynes with nitrogen-containing compounds is one of the most effective and straightforward routes to construct various nitrogen-containing heterocyclic compounds.In this paper,transition metal-catalyzed cyclization of alkyne and enamine in recent years is described.On this basis,it is feasible to develop transition metal-catalyzed cyclization reaction between alkynes and enamine.Pyrido[1,2-a]indoles are the structural units of many alkaloids,which have a wide range of biological activities and drug activities,and are widely used in the fields of organic chemistry,medicinal chemistry,material chemistry,etc.Therefore,the preparation and application of pyrido[1,2-a]indoles have received much attention.In this paper,the method of synthesizing pyrido[1,2-a]indoles is briefly introduced.Comprehensive literature reports,it is practical for one-step construction of pyrido[1,2-a]indoles from a simple and readily available nonfused ring precursors.In this paper,using readily available enamines and electron-deficient terminal alkynes as starting materials together with the development of a new type of cyclization reaction between them as the core,a novel copper-catalyzed cascade bicyclization reaction of enamines with electron-deficient terminal alkynes was developed.This new strategy is simple and efficient,which allows the formation of two rings,three C-C bonds,and one C-N bond in a single step.The series of research results not only created a new type of cyclization reaction between enamines and electron-deficient terminal alkyne,but also provided a convenient method for the construction of polysubstituted pyrido[1,2-a]indole compounds.