Trifluoroacetic acid → 1H-Pyrazolo[3,4-b]pyridine, 4-(2-fluoro-4-nitrophenoxy)-

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Reaction Steps

A stirred mixture of 1-(4-methoxybenzyl)-4-(2-fluoro-4-nitrophenoxy)-1H-pyrazolo[3,4-b]pyridine (27.6 g, 70.0 mmol; obtained from Example 1, Step C) and TFA (53.9 mL, 700 mmol) was heated to reflux for 18 hours under N2. The reaction was allowed to cool to room temperature, and then concentrated in vacuo using toluene (4×100 mL) to azeotrope residual TFA. The residue was diluted with EtOAc (200 mL) and carefully neutralized (pH=8-9) with saturated aqueous NaHCO3 (100 mL). The biphasic suspension was stirred at room temperature for 30 minutes. The suspension was filtered. The resulting solid was dried by toluene azeotrope (2×200 mL) to obtain the product (18.7 g, 97%). 1H NMR (DMSO-d6, 400 MHz) δ 13.85 (br s, 1H), 8.40 (m, 2H), 8.15 (m, 1H), 7.91 (s, 1H), 7.66 (m, 1H), 6.65 (m, 1H).

Provenance & Evidence