Study On Copper-catalyzed Functionalization Of Terminal Alkynes

Copper catalyzed functionalization of terminal alkynes has important application value in organic synthesis.Copper catalyzed C（sp）-H bond coupling reactions and1,2-/1,1-difunctionalizations of terminal alkynes provide a convenient way to access polysubstituted internal alkynes,alkenes,and alkanes.Among them,copper catalyzed multicomponent reactions of terminal alkynes,sulfonyl azides and nucleophiles can provide nitrogen-containing compounds from simple alkynes by one pot procedure,which exhibit a step economy.In addition,copper photosensitizers are not only cheap and easy to obtain,but also have mild toxic properties compared with iridium and ruthenium.At present,the functionalization of alkynes catalyzed by copper photosensitizers remains underdeveloped.Therefore,this thesis studies the copper-catalyzed functionalization of terminal alkynes from two aspects:（1）The copper-catalyzed multicomponent reaction of alkyne,sulfonyl azide and2-bromoallylamine was studied.The reaction was carried out in two steps by one pot procedure:Firstly,cuprous iodide was used as catalyst,triethylamine as base,DMSO as solvent,and the reaction was carried out at room temperature for one hour;Secondly,cuprous iodide,N,N-dimethylethylenediamine and potassium carbonate were added into the reaction mixture,and the reaction was further conducted at 80℃for six hours.Twenty new compounds were obtained in 24 to 77%yields.The structure of the products was confirmed by ¹H NMR,¹³C NMR and HRMS analysis.The mechanistic study indicated that the reaction may undergo a ketenimine intermediate followed by a nucleopilic addition of 2-bromoallylamine,and finally the double C-N coupling reactions to generate the desired product.This reaction has the advantages of simple operation,easy availability of substrates,and good substrate tolerance.（2）Visible light-mediated copper-catalyzed reaction of terminal alkyne with TEMPO was carried out.Under visible light,using terminal alkyne,TEMPO and water as starting materials,acetonitrile as solvent,and Cu（xantphos）（bcp）as copper photosensitizer,the reaction was performed by the reaction at room temperature for12 hours.18 compounds were obtained in 32 to 84%yields.The mechanistic experiments show that both the oxygen atom of carbonyl and the hydrogen atom of theα-methylene in amide derived from water.The proposed reaction mechanism may undergo an oxidation of alkylnyl copper（I）by TEMPO.The formed alkylnyl copper（II）was again oxidized by piperidine nitrogen radical and the ketenimine was transformed to ketone.This reaction has the advantages of mild reaction conditions,no need for the extra addition of oxidant,and easy availability of starting materials.