Nucleophilic aromatic substitution; 1,2-Bis(diphenylphosphino)benzene
Submitted May 02, 2012, published May 07, 2012
Alex Henderson (Alex.Henderson@bris.ac.uk
A contribution from
Bristol Chemical Synthesis DTC
Potassium diphenylphosphide solution, 0.5 M in THF (Sigma-Aldrich)
1,2-Difluorobenzene, 98% (Sigma-Aldrich)
PhMe (Grubbs Solvent System - passed through passed column of alumina)
Activated charcoal (Sigma-Aldrich)
To an anhydrous 0.5 M THF solution of potassium diphenylphosphide (45.0 mL, 22.5 mmol) at RT, was added 1,2-difluorobenzene (1.97 mL, 20.0 mmol) and anhydrous N2 saturated PhMe (50.0 mL). The resulting solution was heated to reflux (110 °C) for 5 h, by which time the dark red colour of the phosphide had dissipated, and 19F NMR spectroscopy showed a single environment (δF: -103.3, d, JFP = 53.0 Hz) correlating to a monophosphine species.§ To the solution at RT, was added an anhydrous 0.5 M THF solution of potassium diphenylphosphide (45.0 mL, 22.5 mmol) and left to reflux (110 °C) for 15 h. P NMR spectroscopy revealed a single peak (δp: -12.3) and the red/orange reaction mixture was concentrated in vacuo. The residue was suspended in PhMe (200 mL) at 70 °C, and activated charcoal (≈ 5.0 g) was added, whilst vigorous stirring occurred. The mixture was hot vacuum filtered through Celite and the solvent was removed in vacuo. The crude material was recrystallised (PhMe) to afford 1,2-bis(diphenylphosphino)benzene (87%, 7.80 g) as a colourless solid.
§No peak observed for 1,2-difluorobenzene (δF: -138.7). P NMR spectrum showed concurrent data (δP: -18.0, d, JPF = 53.0 Hz).
νmax / cm-1 (film): 3056 (w), 1583 (w), 1567 (w), 1476 (m), 1435 (m), 1309 (w), 1157 (w), 1069 (w); mp 186-187 °C (PhMe) [Lit. 183-185 °C (PhMe / EtOH)]; δH (400 MHz, CDCl3): 6.97-7.02 (4H, m, ArCH), 7.08-7.22 (20H, m, ArCH); δC(100 MHz, CDCl3): 128.3 (t, J = 3.5 Hz, ArCH), 128.4 (ArCH), 129.1 (ArCH), 133.9 (t, J = 10.0 Hz, ArCH), 134.1 (t, J = 3.0 Hz, ArCH), 137.1 (t, J = 3.0 Hz, ArC), 143.7 (dd, J = 10.0 and 10.0 Hz, ArC); δp (121 MHz, CDCl3): -13.4.
Baker, B. A.; Bošković, Ž. V.; Lipshutz, B. H. Org. Lett. 2008, 10, 289-292.
McFarlane, H. C. E.; McFarlane, W. Polyhedron
Tunney, S. E.; Stille, J. K. J. Org. Chem. 1987
Keywords: aromatic nucleophilic substitution, aromatics/arenes, carbocyclic compounds, ligand, organo phosphorous