3-Amino-2-chloro-4-methylpyridine → 7-Chloro-1H-pyrazolo[3,4-c]pyridine

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Reaction Steps

A solution of 2-chloro-4-methylpyridin-3-amine [133627-45-9] (3.0 g, 21.0 mmol) in acetic acid (300 mL) was treated with a solution of sodium nitrite (1.45 g, 21.0 mmol) in water (2.5 mL). The reaction mixture was stirred at rt for 15 min then allowed to stand at ambient temperature for 24 h. An additional solution of sodium nitrite (500 mg, 7.25 mmol) in water (1 mL) was added to the mixture which was allowed to stand at rt for 3 h. Acetic acid was evaporated under reduced pressure and the residual aqueous solution was partitioned between EtOAc and sat. aq. NaHCO3. The insoluble solid was filtered off (dried under vacuum; batch 1) and the organic filtrate was washed with water and brine, then dried (Phase separator) and concentrated under vacuum (batch 2). The two batches were combined to give 7-chloro-1H-pyrazolo[3,4-c]pyridine as a solid. MS (LC-MS): 153 [M+H]+, tR (HPLC conditions k): 0.9 min.

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