Copper-catalyzed formal [4 + 1] annulation of N -propargyl ynamides with diketones

An efficient copper-catalyzed formal [4 + 1] annulation of N -propargyl ynamides with diketones is described. This protocol enables practical and atom-economic synthesis of valuable pyrrole-substituted dioxoles in generally moderate to excellent yields under mild reaction conditions. Thus, two new five-membered heterocycles can be constructed in one step through this vinyl cation chemistry.