Substrate scope of alkynes, amines and aldehydes^a.

^aReagents and condition: 1 (1.1 mmol), 2 (1.0 mmol), 3 (1.0 mmol), TsOH (0.1 mmol), H₂O (1.0 mL), under air.

^bIsolated yields.

^cIn H₂O/EtOH (9 : 1, v/v).