Yield: 87%

Reaction Conditions:

with pyridine;hydrogen fluoride;sodium nitrite at 20;Cooling with ice;

Steps:

20.2 Preparation of 3-chloro-5-[2-(1,3-dioxolan-2-yl)ethoxy]-2-fluoropyridine
2) With cooling with ice, sodium nitrite (4.8 g, 70 mmol) was added to a hydrogen fluoride/pyridine (70 % HF) solution (91 ml) of the amine product (12.6 g, 61 mmol) obtained in the above reaction, and stirred at room temperature for 30 minutes. Ice was added to the reaction solution, neutralized with sodium carbonate, extracted with diethyl ether. The organic layer was washed with water and saturated saline water, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The obtained residue was purified by silica gel column chromatography (hexane:ethyl acetate = 80:20) to obtain 5-bromo-3-chloro-2-fluoropyridine (11.1 g, yield: 87 %) as a white solid.

References:

Banyu Pharmaceutical Co., Ltd. EP2221301, 2010, A1 Location in patent:Page/Page column 46