Copper-Catalyzed A3-Coupling: Synthesis of 3-Amino-1,4-diynes

Cu‐catalyzed A3 (amine, aldehyde, and alkyne) coupling reactions were investigated for the synthesis of 3‐amino‐1,4‐diynes. Although metal‐catalyzed A3‐coupling reactions have been extensively used to synthesize various propargylamines, the A3‐coupling for the synthesis of 3‐amino‐1,4‐diynes has been rarely reported. In this study, various symmetrical 3‐amino‐1,4‐diynes were synthesized by the sequential Cu‐catalyzed dealkynylation of propargyl aldehydes followed by A3‐coupling. Unsymmetrical 3‐amino‐1,4‐diynes were also synthesized in 49–85 % yields by Cu‐catalyzed A3‐coupling. Symmetrical and unsymmetrical 3‐amino‐1,4‐diynes are synthesized by copper‐catalyzed coupling of propargyl aldehydes. Copper catalysts are involved in the dealkynylation of propargyl aldehydes and the A3‐coupling reaction.