Copper(I)‐Catalyzed Stereoselective Synthesis of (E)‐α‐Alkynyl‐α,β‐unsaturated Esters from a Terminal Alkyne, Diazoesters and Aldehydes

A new synthetic method for α-alkynyl-α,β-unsaturated esters is presented herein. The method is based on a copper(I)-catalyzed three-component reaction of a terminal alkyne, diazoesters and aldehydes. The reaction is featured by mild conditions, high yields and excellent stereoselectivity. Cu(I) carbene migratory insertion is proposed as the key step in the transformation.