Phosphorus oxybromide → HCID 178468567, compound

Participants

Reaction Conditions

Reaction Steps

A mixture of 6-hydroxy-3-methyl-1H-pyrazolo[3,4-b]pyridine-4-carboxylic acid ethyl ester (13.7 g) and phosphorous oxybromide (19.5 g) in toluene (300 mL) was stirred at 110° C. for 5 h, cooled to r.t., and added dropwise into an ice cold solution of potassium acetate (18.2 g) in water (300 mL). The mixture was extracted twice with ethyl acetate, the combined organic phases were washed with brine, dried over magnesium sulfate and concentrated in vacuo. 6-Bromo-3-methyl-1H-pyrazolo[3,4-b]pyridine-4-carboxylic acid ethyl ester (4.6 g, 26%) were obtained. This material was dissolved in THF (60 mL), and 3,4-dihydro-2H-pyran (1.6 mL) and p-toluenesulfonic acid monohydrate (0.91 g) were added. The solution was stirred at r.t. for 48 h, then 3,4-dihydro-2H-pyran (1.6 mL) were added and the solution stirred again for 48 h. The mixture was poured into water and extracted with ethyl acetate, the organic layer was dried over magnesium sulfate and concentrated in vacuo. The residue was purified by flash chromatography (silica, heptane/ethyl acetate gradient). 2.2 g (38%) of the title compound were obtained.

Provenance & Evidence