Copper-Catalyzed Difunctionalization of Terminal Alkynes with Diazo Esters and Amines to Construct -Enamino Esters

An operationally simple and efficient copper-catalyzed three-component tandem reaction of terminal alkynes, diazo compounds and amines to yield -enamino esters is described. This straightforward protocol takes place rapidly with a wide range of substrates and gives the desired -enamino esters in good to excellent yields. Preliminary mechanistic studies suggested that the reaction probably proceeds through Cu-catalyzed formal C-H insertion to produce an alkynoate intermediate, which was then trapped by amines to give the -enamino esters.