3,4-dihydro-2H-pyran → 6-chloro-3-iodo-1-(tetrahydro-pyran-2-yl)-1H-pyrazolo[3,4-b]pyridine-4-carboxylic acid ethyl ester

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Reaction Steps

To a solution of 6-chloro-3-iodo-1H-pyrazolo[3,4-b]pyridine-4-carboxylic acid ethyl ester (14 g, 39.8 mmol) and p-toluenesulfonic acid monohydrate (0.75 g, 3.9 mmol) in anhydrous chloroform (200 ml) at 0° C. was added dropwise 3,4-dihydro-2H-pyran (5.45 ml, 59.7 mmol). The reaction mixture was allowed to warm to room temperature, stirred overnight and concentrated under reduced pressure. The residue was subjected to silica gel column chromatography using a stepwise gradient of ethyl acetate (0-20%) in cyclohexane to afford the title compound as a yellow solid (9.4 g, 54%). LC/MS (Method LC8): Rt=2.08 min; m/z=351 [M+H-THP]+.

Provenance & Evidence