Aluminium lithium hydride → 5-bromo-1-(tetrahydro-2H-pyran-2-yl)-1H-pyrazolo[3,4-b]pyridine-3-carbaldehyde

To a solution of 5-bromo-N-methoxy-N-methyl-1-(tetrahydro-2H-pyran-2-yl)-1H-pyrazolo[3,4-b]pyridine-3-carboxamide (X) (0.290 g, 0.78) in dry THF (5 mL) stirred at 0° C. under nitrogen was added lithium aluminum hydride (36 mg, 0.94 mmol). The solution was further stirred at 0° C. for 30 min. The reaction was quenched with a 0.4 N NaHSO4 solution (10 mL). The solution was extracted with DCM (3×15 mL). The combined organic layer was washed subsequently with water and brine. The organic layer was dried over MgSO4, filtered and concentrated under reduced pressure to produce 5-bromo-1-(tetrahydro-2H-pyran-2-yl)-1H-pyrazolo[3,4-b]pyridine-3-carbaldehyde (XI) as a viscous liquid (218 mg, 0.70 mmol, 91% yield). 1H NMR (CDCl3) δ ppm 1.52-1.74 (m, 2 H), 1.95-2.18 (m, 2H), 2.37-2.49 (m, 2H) 3.87-3.98 (m, 1 H), 3.99 (m, 1H), 6.18 (dd, J=10.20, 2.39 Hz, 1 H), 8.73 (d, J=3.01 Hz, 1 H), 8.85 (d, J=3.01 Hz, 1 H), 10.16 (s, 1 H); ESIMS Found for C12H12BrN3O2 m/z 310.4 (M+H).