Benzonitrile → 7-Bromo-2-phenyl-[1,2,4]triazolo[1,5-A]pyridine

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A mixture of 2-amino-4-bromopyridine (0.50 g, 2.89 mmol), copper (I) bromide (20.7 mg, 0.14 mmol), 1,10-phenanthroline monohydrate (28.9 mg, 0.14 mmol), zinc iodide (92.3 mg, 0.29 mmol), benzonitrile (298 mg, 0.29 mL, 2.89 mmol) and 1,2-dichlorobenzene (25 mL) was heated in a 100-mL 3-necked flask to 130° C. During 22 h a gentle flow of air was bubbled through the reaction mixture (69% conversion, HPLC method cf. example 1.3). The dark brown suspension was then cooled to 0-5° C. and filtered. The filter cake was washed with EtOAc (30 mL) and the combined filtrates were concentrated on vacuum such that most EtOAc was evaporated off. The resulting solution of the crude product in 1,2-dichlorobenzene was then loaded on a silica gel column to yield after chromatography (hexane/EtOAC from 9:1 to 7:3) 7-bromo-2-phenyl-[1,2,4]triazolo[1,5-a]pyridine (345 mg, 41%) as an off-white solid with 97.6% purity (HPLC area-%, HPLC method cf. comparative example 1) containing as an non-separable impurity 1.4% of 7-iodo-2-phenyl-[1,2,4]triazolo[1,5-a]pyridine.

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