Diisopropylamine → 1-(3-Fluorophenyl)-4-hydroxy-7-methyl-1H-pyrazolo[3,4-b]pyridin-6(7H)-one

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Reaction Steps

A solution of diisopropylamine (3.45 mL, 24.4 mmol) in 15 mL THF under argon at 0° C. was treated with n-butyllithium (14.7 mL of 1.6 M solution in hexanes, 23.5 mmol) and stirred at this temperature for 30 min. The freshly prepared LDA was added dropwise to a solution of ethyl 1-(3-fluorophenyl)-5-(N-methylacetamido)-1H-pyrazole-4-carboxylate (2.87 g, 9.40 mmol) in 5 mL of THF at −78° C. After the reaction mixture was gradually warmed to RT in 4 h, it was partitioned between 1N NaOH and 45 mL of ether. The ether layer was separated and discarded; the aqueous layer was acidified with 2 N HCl, and extracted three times with EtOAc. The combined EtOAc layers were washed with brine, dried over MgSO4, and concentrated to yield the title compound as a tan crystalline solid. MS (ESI, pos.ion) m/z: 260.1 (M+1). The crude material was used in the next step without further purification.

Provenance & Evidence