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

1,7-Dihydro-pyrazolo[3,4-b]pyridin-4-one (1.2 g, 8.8 mmol) (Dorn, H. et al., Prakt. Chem., 324, 557–62 (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 8.57 (d, 1H, J=5.2 Hz), 8.25 (s, 1H), 7.28 (d, 1H, J=5.2 Hz).

1. temperatureheated to 90° C.
2. concentrationThe solution was concentrated under reduced pressure
3. additiontreated with ice and water (50 ml)
4. extractionThe resulting mixture was extracted with ethyl acetate (100 ml)
5. washthe organic layer was washed with a saturated aqueous solution of sodium bicarbonate (30 ml)
6. dry with materialThe organic layer was dried over MgSO4
7. customevaporated under reduced pressure

ORD record

ord-cc3538d4378d4ee1af5026a43d61899d

Source dataset

uspto-grants-2006_11

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07141587B2