Stereoselective Access to ( E)-1,3-Enynes through Pd/Cu-Catalyzed Alkyne Hydrocarbation of Allenes.

PdII and CuI cooperate in catalyzing the alkynes hydrocarbation of allenes (AHA) giving ( E)-1,3-enynes with high yields, atom economy, and high regio-/stereoselectivities. We devised new efficient conditions and expanded the substrate scope. Experimental and computational studies support a nonorthodox PdII/PdIV catalytic cycle involving an oxidative addition triggered by a stereodeterminant H+ transfer. This reaction is leveraged in a new strategy of stereoselective synthesis of 1,3-dienes.