Ethyl chloroformate → [6-(4-Benzyloxy-2-fluoro-phenyl)-3-methyl-1-(tetrahydro-pyran-2-yl)-1H-pyrazolo[3,4-b]pyridin-4-yl]-methanol

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Reaction Steps

At 0° C. to a solution of 3.00 g of 6-(4-benzyloxy-2-fluoro-phenyl)-3-methyl-1-(tetra-hydro-pyran-2-yl)-1H-pyrazolo[3,4-b]pyridine-4-carboxylic acid in 50 ml of dry tetrahydrofurane were added 1.2 ml of Hünig's base, followed by slow addition of 0.7 ml of ethyl chlorformate. After 30 min at 0° C. the resulting suspension was filtered. Under argon atmosphere to the filtrate were added 290 mg of sodium borohydride and 15 ml of water. After 2 h at 0° C. sat. aqueous ammonium chloride solution was added. The layers were separated and the aqueous layer was extracted with methyl tert-butyl ether. The combined organic layers were dried over sodium sulphate, filtered and concentrated in vacuo. 1.60 g (55%) of the title compound were obtained.

Provenance & Evidence