Reaction Steps
Ethyl 1-(2,4-difluorobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-carboxylate. To a stirred solution of ethyl 1H-pyrrolo[2,3-c]pyridine-5-carboxylate [prepared according to M. Dekhane, P. Potier, R. H. Dodd, Tetrahedron, 1993, 49, 8139-8146](0.50 g, 2.63 mmol) in DMF (10 mL) under a nitrogen atmosphere was added sodium hydride (0.087 g, 80% in mineral oil, 2.89 mmol) and 2,4-difluorobenzyl bromide (0.60 g, 2.89 mmol). The resulting mixture was stirred for 16 hours at ambient temperature. It was quenched with water (30 mL), and extracted with ethyl acetate (3×30 mL). The combined organic extracts were washed with water (2×30 mL), dried over sodium sulfate, concentrated in vacuo and purified by flash chromatography. Elution with hexane:ethyl acetate (1:1) provided the title compound as a light yellow solid (0.40 g, 48% yield). 1H NMR (CD3OD) δ8.86 (s, 1H), 8.47 (s, 1H), 7.71 (d, 1H, J=3.2 Hz), 7.31 (dd, 1H, J=6.3 Hz), 6.94-7.05 (m, 2H), 6.79 (d, 1H, J=3.2 Hz), 5.63 (s, 2H), 4.46 (q, 2H, J=7.3 Hz), 1.45 (t, 3H, J=7.3 Hz). LCMS (API-ES, M+H+): 317.0. (b) 1-(2,4-Difluorobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-carboxylic acid. To ethyl 1-(2,4-difluorobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-carboxylate (0.30 g, 1.58 mmol) in methanol (3 mL) was added sodium hydroxide (0.076 g, 3.16 mmol) in water (0.5 mL). The reaction was heated in a SmithCreator™ (microwave reactor from Personal Chemistry) to 100° C. for five minutes. The reaction solution was poured into water (30 mL) and the pH was adjusted to 2-3 by addition of citric acid. The precipitate that formed was collected by filtration and dried in vacuo to provide the title compound as a white powder (0.15 g, 55% yield). 1H NMR (DMSO-d6): δ: 8.97 (s, 1H), 8.35 (s, 1H), 7.82 (d, 1H, J=3.2 Hz), 7.28-7.38 (m, 2H), 7.09 (t, 1H, J=8.4 Hz), 6.76 (d, 1H, J=3.2 Hz), 5.67 (s, 2H). LCMS (API-ES, M+H+): 289.1. (c) 1-(2,4-Difluorobenzyl)-N-hydroxy-1H-pyrrolo[2,3-c]pyridine-5-carboxamide. To 1-(2,4-difluorobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-carboxylic acid (0.15 g, 0.52 mmol) in DMF (10 mL) were added 0-(7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HATU; 0.20 g, 0.52 mmol), triethylamine (0.15 ml, 1.05 mmol), and hydroxylamine hydrochloride (0.036 g, 0.52 mmol). The resulting mixture was stirred for 16 hours at ambient temperature. It was quenched with water (30 mL), extracted with ethyl acetate (3×30 mL). The combined organic extracts were washed with water (2×30 mL), dried over sodium sulfate, concentrated in vacuo and purified by preparative HPLC to provide the title compound as a white powder (0.075 g, 48% yield). 1H NMR (DMSO-d6) δ: 11.14 (s, 1H), 8.92 (s, 1H), 8.85 (s, 1H), 8.21 (s, 1H), 7.78 (s, 1H), 7.26-7.38 (m, 2H), 7.08 (t, 1H, J=8.3 Hz), 6.71 (d, 1H, J=3.0 Hz), 5.64 (s, 2H). LCMS (API-ES, M+H+): 304.1. HRMS calcd for C15H12F2N3O2 (M+H) 304.0898, found 304.0886. HPLC: 98% purity.
