Copper-Catalyzed Cross-Coupling/[2+2]Cycloaddition Of Diazo Compounds And Enynes

Copper-catalyzed cross-coupling of diazo compounds and terminal alkynes is a hot topic in the field of diazo chemistry.It is not only provides a new route for the synthesis of allenes,but also produces carbon(hetero)ring compounds further.However,there are few reports on cycloaddition reactions based on allene intermediates.In this paper,copper-catalyzed cross-coupling [2 + 2] cycloaddition of alkynes with diazo compounds were studied,which were used the near end of double bond to synthesize cyclobuta[b]indoles.At present,the structure of cyclobuta[b]indole has not been found in the field of natural medicine research.Compare to use non indole structure compounds to synthesize cyclobuta[b]indoles,indole structure compounds which were used to synthesize cyclobuta[b]indoles were normal in the field of organic synthesis.Therefore,it is necessary to construct the cyclobuta[b]indole efficiently.This paper is divided into two parts.The first part focuses on the copper-catalyzed cross-coupling of diazo compounds and terminal alkynes to produce allene intermediates,and such various cyclizations and cycloaddition reactions can be occured subsequently.In the second part,the significances and methods of synthesizing cyclobuta[b]indoles were introduced.According to the previous work of our research group on allenyne,we designed enynes and diazo compounds to screen different catalysts and solvents.Because the products have two configurations of Z and E,the geometric selectivity was poor,so the conditions of Z and E selectivity are explored,and finally the substrate was expanded.It was found that the Generality,Chemoselectivity and Regioselectivity were excellent.In the process of expanding the structures of aliphene-alkynes,the intermediates were obtained by the optimal conditions.And only by heating the reaction could we get the target product.The reaction mechanism was studied.