One-Pot Synthesis of Unsymmetrical 1,4-Diaminobutynes by Cu(I)-Catalyzed Cross-Coupling of Propiolic Acid, Secondary Amine, Aldehydes and Formaldehyde

A highly selective and efficient copper-catalyzed sequential approach for the one-pot two-step synthesis of unsymmetrical 1,4-diamino-2-butynes from propiolic acid, secondary alkylamine, aldehyde and formaldehyde solution has been developed. The process of this reaction was involved in the generation of key intermediate propargylamines which were obtained via decarboxylative A3-coupling reaction. After that, the intermediate propargylamines would react with in situ formed iminium ions to give the cross-coupling target products in moderate to excellent yields under microwave irradiation.