Trifluoroacetic acid → tert-butyl 3-(4-(3,4-difluoro-2-(trifluoromethyl)phenyl)piperidine-1-carbonyl)-6,7-dihydro-1H-pyrazolo[4,3-c]pyridine-5(4H)-carboxylate

Participants

Reaction Steps

To a solution of tert-butyl 4-(3,4-difluoro-2-(trifluoromethyl)phenyl)piperidine-1-carboxylate (9, 41.1 g, 113 mmol) in CH2Cl2 (50 mL) was added TFA (50 mL). The mixture was stirred at ambient temperature for 1 h and was concentrated under reduced pressure. The residue was dissolved in DMF (240 mL) and to this solution was added N,N-diisopropylethylamine (72.4 g, 560 mmol), followed by 5-(tert-butoxycarbonyl)-4,5,6,7-tetrahydro-1H-pyrazolo[3,4-c]pyridine-3-carboxylic acid (30.1 g, 113 mmol), and HBTU (74.7 g, 169 mmol). The mixture stirred at ambient temperature for 16 h, was diluted with EtOAc (1 L) and washed with H2O (1.4 L). The organic layer was washed with brine (3×600 mL), dried over Na2SO4, filtered, and concentrated under reduced pressure. The resulting residue was chromatographed over silica gel (30-80% EtOAc in hexanes) to give tert-butyl 3-(4-(3,4-difluoro-2-(trifluoromethyl)phenyl)piperidine-1-carbonyl)-6,7-dihydro-1H-pyrazolo[4,3-c]pyridine-5(4H)-carboxylate (35) as a white solid (0.068 g, 80%): 1H NMR (300 MHz, CDCl3) δ10.23 (br, 1H), 7.36-7.28 (m, 1H), 7.15 (m, 1H), 4.86 (br, 2H), 4.62 (s, 2H), 3.72 (br, 2H), 3.27-2.74 (m, 5H), 1.90-1.64 (m, 4H), 1.48 (s, 9H); MS (ESI+) m/z 515 [M+H]+.

Provenance & Evidence