4,6'-DICHLORO-2,2'-BIPYRIDINE synthesis

Yield:1762-41-0 52% ，85591-65-7 33%

Reaction Conditions:

with trichlorophosphate at 80; for 4 h;

Steps:

4.2.2. 4,4'-Dichloro-2,2'-bipyridine (5) and 4,6'-dichloro-2,2'-bipyridine(6).

N-Oxide 2¹⁷ (0.78 g, 3.6 mmol) was slowly added with stirring to POCl₃ (3.0 mL, 33 mmol, 9.1 equiv) at 0 °C. The mixture was stirred at 80 °C for 4 h. The excess of POCl₃ was removed under reduced pressure (15 Torr). Ice-cold water (10 mL) was added to the residue and the mixture was neutralized with 40% aqueous NaOH. The solution was extracted with EtOAc (3×30 mL) and the combined organic extracts were dried over anhydrous Na₂SO₄. The solvent was evaporated to give a brownish solid (0.78 g), which was subjected to column chromatography (Al₂O₃, EtOAc/n-hexane 1:7) to afford pure compounds 5 and 6: 4,4′-dichloro-2,2′-bipyridine (5), colorless powder, (0.42 g, 52%), mp 133-134 °C (lit.^18a mp 130 °C); R_f 0.70 (Al₂O₃, n-hexane/EtOAc 20:1); δ_H (CDCl₃) 8.57 (2H, d, J=5.1 Hz), 8.45 (2H, s), 7.35 (2H, dd, J=1.7, 5.1 Hz); δ_C (CDCl₃) 156.4, 150.1, 145.5, 124.5, 121.9; HRMS: MH⁺, found 224.9979, MNa⁺, found 246.9797. C₁₀H₆Cl₂N₂ required 224.9981 and 246.9800. 4,6′-dichloro-2,2′-bipyridine (6), beige solid, (0.27 g, 33%), mp 102-103 °C [lit.^18c mp 87.5-89 °C]; R_f 0.47 (Al₂O₃, n-hexane/EtOAc 20:1); δ_H (CDCl₃) 8.56 (1H, d, J=5.1 Hz), 8.45 (1H, s), 8.35 (1H, d, J=7.7 Hz), 7.78 (1H, t, J=7.8 Hz), 7.32-7.41 (2H, m); δ_C (CDCl₃) 156.1, 155.5, 151.1, 150.1, 145.5, 139.6, 124.9, 124.4, 121.8, 119.8; HRMS: MH⁺, found 224.9982. M=C₁₀H₆Cl₂N₂ required 224.9981. MNa⁺, found 246.9794, required 246.9800.

References:

Zavozin, Alexander G.;Simirskaya, Nina I.;Nelyubina, Yulia V.;Zlotin, Sergei G. [Tetrahedron,2016,vol. 72,# 47,p. 7552 - 7556]