Phosphorus pentachloride → 3,5-Dibromo-4-chloropyridine

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Reaction Conditions

Reaction Steps

A mixture of 3,5-dibromo-4-pyridone (VIII, W=Br) (79.0 g, 0.312 mol) and PCl5 (79 g, 0.38 mol) was kept at 160° C. for 3 h. The reaction mixture was cooled to 0° C. and quenched by slow addition of water (200 mL). The resulting precipitate was crushed, filtered off, washed with water, and transferred on top of a flash silica column which was subsequently eluted with CH2Cl2. The crude product thus obtained was crystallised from EtOH to give the title compound, 3,5-dibromo-4-chloropyridine (VII, W=Br) (73.9 g, 72%) as white needles: Rf=0.60 (CH2Cl2); mp 95.0-96.5° C. (EtOH); 1H NMR (250 MHz, CDCl3) δ8.65 (s); 13C NMR (63 MHz, CDCl3) δ121.8, 144.0, and 150.9; IR (CHCl3) νmax 1549, 1524, 1410, and 1394 cm−1; MS (EI+) m/z (rel intensity) 271 (100%, M+) and 192 (30); HRMS calcd for C5H2Br2ClN (M+) 268.8242. found 268.8231.

Provenance & Evidence