General procedure for Cu3NC(NHC)-catalyzed the A3 coupling reaction in 2 mmol scale

Under N₂ atmosphere, the catalyst of Cu₃NC^(NHC) (46 mg, 1.2 mol%), activated MS 4 Å sieves (5.0 g) and dry DCM (15.0 mL) were added into the dry Schlenk tube. The reaction mixture was stirred at room temperature for 5 min. Benzaldehyde 1 (213 mg, 2.0 mmol, 1.0 eq.) and phenylacetylene 2 (205.0 mg, 2.0 mmol, 1.0 eq. were then added to the stirred mixture. The reaction mixture was stirred at room temperature for 5 min. Dibenzylamine 3 (592.0 mg, 3.0 mmol, 1.5 eq.) and dry DCM (5.0 mL, 0.1 M) were added into the stirred mixture of the Schlenk tube. The reaction was stirred at room temperature for 12 h. The reactions were monitored by TLC. When Benzaldehyde 1 and Phenylacetylene 2 were consumed, the reaction was quenched and concentrated. The crude product was then purified by column chromatography (PE-EA, v/v 10/1) to give the N, N-dibenzyl-1,3-diphenylprop-2-yn-1-amine (4a) as colorless oil with overall isolated yield: 95% (735.7 mg).