Copper-promoted Cyclization Of Hydrazones For The Synthesis Of Heterocycles

The synthesis of nitrogen-containing heterocycles compounds has an important application in organic reaction.Many drugs contain nitrogen-containing heterocycles skeleton.Not only that,but also in organic catalyst synthesis,which can be used to develop new synthetic methods,for example,N-heterocyclic Carbene is an important class of catalysts organic reaction.In organic synthesis reactions,a series of Nheterocyclic Carbene catalyzed organic reactions have been developed,which is an important branch of organic small molecule catalysis.Based on these advantage,the synthesis of nitrogen-containing heterocycles compounds has become a cutting edge in organic chemistry.It is important to develop new methods to synthesize nitrogencontaining heterocycles compounds.In recent years,many effects have been made for using β,γ-unsaturated hydrazone to synthesize nitrogen-containing heterocycles compounds,mainly through radical reactions,transition metal catalyzed and other types of reactions to synthesize five-and six-membered nitrogen-containing heterocycles compounds.However,we should pay attention to the limitations of these methods.For example,in the reaction of synthesizing six-membered nitrogen-containing heterocycles compounds,when using β,γ-unsaturated hydrazone as the substrate,only the β position of the substrate must be superseded by methyl or phenyl can formation six-membered nitrogen-containing heterocycles compounds by 6-endo-trig type cyclization reaction,the limitations of the substrate is relatively large,which greatly limits the application of this method in the synthesis.Therefore,it is necessary to develop a wide scope of substrates,mild conditions and high selectivity method to achieve 6-endo-trig type cyclization of the β,γ-unsaturated hydrazone.Copper complexes are used as catalysts in modern synthetic chemistry because of their low cost,versatile reactivity,and broad tolerance for functional groups on substrates.Copper-promote reactions have a long history in organometallic chemistry and new reactions continue to be discovered and developed.Therefore,we assumed that using β,γ-unsaturated hydrazone as the substrate,using copper complexes to promote β,γ-unsaturated hydrazone cyclization,to generate six-membered Nheterocycles compounds is a convenient method.Herein,we reported that copper acetate(II)promotes the 6-endo-trig type reaction of β,γ-unsaturated hydrazone.A series of six-membered nitrogen-containing heterocycles compounds have been synthesized by this method with excellent selectivity,yield,and wide scope of substrates.