Sodium Thiosulfate → 5-bromo-1-trityl-1H-pyrazolo[3,4-b]pyridine-3-carbaldehyde

Participants

Reaction Conditions

Reaction Steps

To a solution of (5-bromo-1-trityl-1H-pyrazolo[3,4-b]pyridin-3-yl)methanol (XXIII) (4.05 Kg, 8.6 mol) in DCM (97 L) was added a solution of KBr (205 g, 1.72 mol) in water (4 L). The solution was cooled to 0° C. before adding TEMPO (107.5 g, 688 mmol) and stirring for 30 min. To this solution was added a solution of KHCO3 (10.8 Kg, 107.4 mol) and aqueous 7% NaClO (13.4 L) in water (40 L). The reaction was stirred at 0° C. for 18 hours. A solution of Na2S2O3*5H2O (1.4 Kg, 5.7 mol) in water (9.1 L) was added dropwise to the reaction at 0° C. and stirred for 30 min. The aqueous layer was then separated and washed with DCM (48 L). The combined organic phases were washed with aqueous 25% NaCl (48 L), dried over Na2SO4, filtered and concentrated under vacuum. The residue was co-evaporated with 3×MeOH (20 L) and the solid was washed with 2×n-heptane (8 L). The solid was dried under vacuum at 45° C. to give 5-bromo-1-trityl-1H-pyrazolo[3,4-b]pyridine-3-carbaldehyde (XXIV) (3.25 Kg, 6.94 mol, 92.3% purity, 80.6% assay yield). 1H NMR (CDCl3, 400 MHz) δ ppm 7.19 (d, J=6 Hz, 5H), 7.22-7.34 (m, 10H), 8.28 (d, J=2.4 Hz, 1H), 8.70 (d, J=2.4 Hz, 1H), 10.07 (s, 1H); ESIMS found C26H18BrN3O m/z 490.0 (M+Na).

Provenance & Evidence