Efficient and recyclable Cu₂(BDC)₂(BPY)-catalyzed oxidative amidation of terminal alkynes: role of bipyridine ligand

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Summary:
The authors from Ho Chi Minh City University of Technology (VNU-HCM) developed a porous MOF catalyst Cu₂(BDC)₂(BPY) with high Cu-bipyridine sites, achieving efficient, selective and recyclable oxidative amidation of terminal alkynes under O₂ in toluene.

Background:
1. To access ynamides, earlier protocols used homogeneous CuCl₂ or solid Cu-MOFs but required slow alkyne addition, excess amide, or suffered from catalyst decomposition and limited scope.
2. The team now propose a ligand-stabilized Cu-paddle-wheel MOF and obtain 90 % isolated yield with 95 % selectivity under mild, scalable conditions.

Research Content:
1. Synthesis: Solvothermal reaction of Cu(NO₃)₂·3H₂O, H₂BDC and 4,4′-bipyridine in DMF (120 °C, 24 h) followed by solvent exchange and 170 °C activation gives green crystalline Cu₂(BDC)₂(BPY) (75 % yield).
2. Characterizations:
   1) BET 970 m² g⁻¹, micro-pores 7–12 Å.
   2) SEM/TEM 200–500 nm rectangular plates; XRD confirms highly crystalline paddle-wheel network.
   3) FT-IR 1615 cm⁻¹ (C=N), ICP 20.8 % Cu, H₂-TPR shows reducibility, TGA stable to 280 °C.
3. Application: 20 mol % MOF, NaHCO₃, O₂ (1 atm), toluene 80 °C, 4 h converts phenylacetylene + 2-oxazolidinone → 3-(phenylethynyl)oxazolidin-2-one in 90 % isolated yield; 15 substrates (aromatic/aliphatic alkynes, sulfonamides, oxazolidinones) give 31–96 % yield. Catalyst recycled 5× with <8 % activity loss.
4. Mechanism: Bipyridine ligands stabilize Cu-paddle-wheel nodes against hydrolysis; O₂ activates Cu(I)→Cu(II) cycle; no Cu leaching (<30 ppm) and hot-filtration confirm true heterogeneous catalysis.

Outlook:
The study delivers a robust, reusable MOF catalyst that merges porosity with redox-active Cu centers, offering a green, practical route to valuable ynamides and expanding MOF utility in C–N bond formation.

Efficient and recyclable Cu₂(BDC)₂(BPY)-catalyzed oxidative amidation of terminal alkynes: role of bipyridine ligand
Authors: Hanh T. N. Le, Thuan V. Tran, Nam T. S. Phan, Thanh Truong
DOI: 10.1039/c4cy01074d
Link: https://pubs.rsc.org/en/content/articlelanding/2015/cy/c4cy01074d

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