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

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Reaction Steps

To a solution of tert-butyl 4-(3,4-difluoro-2-(trifluoromethyl)phenyl)piperidine-1-carboxylate (9, 0.100 g, 0.27 mmol) in CH2Cl2 (10 mL) was added TFA (2 mL). The mixture was stirred at ambient temperature for 1 h and was concentrated under reduced pressure. The residue was dissolved in DMF (2 mL) and to this solution was added 5-(tert-butoxycarbonyl)-1,4,5,6-tetrahydropyrrolo[3,4-c]pyrazole-3-carboxylic acid (0.073 g, 0.28 mmol), HBTU (0.191 g, 0.43 mmol), and N,N-diisopropylethylamine (0.11 g, 0.864 mmol). The mixture stirred at ambient temperature for 16 h and was diluted with EtOAc, washed with brine, dried over Na2SO4, filtered, and concentrated under reduced pressure. The resulting residue was chromatographed over silica gel (0-90% EtOAc in hexanes) to give tert-butyl 3-(4-(3,4-difluoro-2-(trifluoromethyl)phenyl)piperidine-1-carbonyl)-4,6-dihydropyrrolo[3,4-c]pyrazole-5(1H)-carboxylate (37) as a white solid (0.132 g, 91%): 1H NMR (300 MHz, CDCl3) δ 10.39 (br, 1H), 7.38-7.30 (m, 1H), 7.15-7.08 (m, 1H), 4.80-4.26 (m, 6H), 3.26-3.20 (m, 2H), 2.92 (br, 1H), 1.96-1.66 (m, 4H), 1.51 (s, 9H); MS (ESI+) m/z 501 [M+H]+.

Provenance & Evidence