Phosphorus pentachloride → 4-Chloro-1H-pyrazolo[3,4-b]pyridine

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Reaction Steps

1,7-Dihydro-pyrazolo[3,4-b]pyridin-4-one (1.2 g, 8.8 mmol) (Dorn, H. et al., Prakt. Chem., 324, 55762 (1982)) in POCl3 (15 ml) at 0° C. was treated with PCl5 (2.5 mg, 0.01 mmol). The solution was allowed to warm to rt over 1 h, then heated to 90° C. and held 3 h. The solution was-concentrated under reduced pressure, then treated with ice and water (50 ml). The resulting mixture was extracted with ethyl acetate (100 ml), and the organic layer was washed with a saturated aqueous solution of sodium bicarbonate (30 ml). The organic layer was dried over MgSO4, then evaporated under reduced pressure to give 4-chloro-1H-pyrazolo[3,4-b]pyridine as a yellow solid (820 mg, 60%). 1H NMR (300 MHz, CDCl3) δ 857 (d, 1H, J=5.2 Hz), 8.25 (s, 1H), 7.28 (d, 1H, J=5.2 Hz).

Provenance & Evidence