MIL-101(Cr)-SO₃Ag: An efficient catalyst for solvent-free A³ coupling reactions

An Ag(I)-functionalized MOF, MIL-101-SO₃Ag, was synthesized and demonstrated to be an efficient and environmentally friendly catalyst for the syntheses of propargylamines through A³ coupling of aldehydes, terminal alkynes and amines. A quite small amount of the catalyst can efficiently catalyze the reactions of aliphatic aldehydes, alkynes, and amines under solvent-free conditions to give propargylamines in excellent yields (>90%). The TOF can be as high as 6600 h⁻¹. The catalytic efficiency is higher than other catalysts available in the literature. The catalyst could be easily recycled without a significant loss of its catalytic activity. In addition, we found that the catalyst also promotes the secondary reaction in which the propargylamines formed from aromatic aldehydes undergo propargyl-to-allenyl isomerization and subsequent hydrolysis to give chalcones.