Trityl chloride → 4-iodo-1-trityl-1H-pyrazolo[3,4-b]pyridine

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Reaction Conditions

Reaction Steps

4-iodo-1H-pyrazolo[3,4-b]pyridine (15 g, 61.22 mmol) was dissolved in dimethylformamide (300 mL) and the solution was cooled down in an ice bath to 5° C. Sodium hydride (60%, 2.938 g, 73.46 mmol) was added portionwise and left to stir at this temperature for 2 hours. After this time a solution of trityl chloride (18.77 g, 67.34 mmol) in dimethylformamide (150 mL) was added dropwise over 30 minutes. After an additional 2 hours of stirring, the solvent was removed by evaporation, and the residue was partitioned between ethyl acetate and saturated bicarbonate (2×100 ml). The organic layer was further washed with brine (100 ml), dried over magnesium sulfate and concentrated in vacuo to give a brown oil. This residue was purified on silica gel by flash column chromatography to afford the title compound as a white solid (less polar fraction: 2-regioisomer, 13.71 g, 46% yield; more polar fraction: 3-regioisomer, pale yellow solid, 8.06 g, 27% yield).

Provenance & Evidence