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

Temperature

0 °C

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.

1. customquenched by slow addition of water (200 mL)
2. customThe resulting precipitate was crushed
3. filtrationfiltered off
4. washwashed with water
5. washwas subsequently eluted with CH2Cl2
6. customThe crude product thus obtained
7. customwas crystallised from EtOH

ORD record

ord-9c117d39833a4d84b2f932c3b7f516c3

Source dataset

uspto-grants-2007_11

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07291739B2