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TCI Practical Example: Sonogashira Cross Coupling with PdCl₂(PPh₃)₂ as a Catalyst

We would like to introduce the Sonogashira cross coupling of iodobenzene and ethynylbenzene using a palladium catalyst.

Used Chemicals

• Iodobenzene [I0050]
• Ethynylbenzene [E0196]
• Bis(triphenylphosphine)palladium(II) Dichloride [B1667]
• Copper(I) Iodide [C2163]
• Triethylamine [T0424]
• Tetrahydrofuran Anhydrous [T2394]

Procedure

To a two-necked flask was charged with iodobenzene (1.09 mL, 9.80 mmol, 1.0 equiv.), ethynylbenzene (1.18 mL, 10.7 mmol, 1.1 equiv.), bis(triphenylphosphine)palladium(II) dichloride (137 mg, 0.195 mmol 2.0 mol%), copper(I) iodide (40 mg, 0.210 mmol, 2.1 mol%), tetrahydrofuran anhydrous (40 mL), triethylamine (1.90 mL, 14.7 mmol, 1.5 equiv.) under nitrogen atmosphere. The mixture was stirred at room temperature for 1.5 h. The reaction mixture was quenched with water (20 mL). The organic layer was washed with brine (10 mL), dried over Na₂SO₄ and then concentrated under reduce pressure. The crude was purified by column chromatography on silica gel (hexane) to afford diphenylacetylene as a white powder (1.70 g, 97 %).

Experimenter's Comments

The reaction mixture was monitored by GC.

Analytical Data

Diphenylacetylene

¹H NMR (400 MHz, CDCl₃); δ 7.51-7.54 (m, 4H), 7.31-7.35 (m, 6H).

¹³C NMR (101 MHz, CDCl₃); δ 131.6, 128.3, 128.2, 123.2, 89.3.

Other References

• A convenient synthesis of acetylenes: catalytic substitutions of acetylenic hydrogen with bromoalkenes, iodoarenes and bromopyridines
  • K. Sonogashira, Y. Tohda, N. Hagihara, Tetrahedron Lett. 1975, 16, 4467.