[NH2:1][C:2]1[CH:7]=[C:6]([F:8])[C:5]([F:9])=[CH:4][C:3]=1[NH:10][C:11](=O)[C@@H:12]([NH:14][C:15](=[O:21])[O:16][C:17]([CH3:20])([CH3:19])[CH3:18])[CH3:13]>CC(O)=O>[F:9][C:5]1[C:6]([F:8])=[CH:7][C:2]2[NH:1][C:11]([C@@H:12]([NH:14][C:15](=[O:21])[O:16][C:17]([CH3:20])([CH3:19])[CH3:18])[CH3:13])=[N:10][C:3]=2[CH:4]=1A mixture of (S)-tert-butyl 1-(2-amino-4,5-difluorophenylamino)-1-oxopropan-2-ylcarbamate (3.454 g, 10.96 mmol) in AcOH (21.91 mL) was heated at 75° C. After 50 min, the mixture was concentrated in vacuo. The residue was dissolved in DCM (100 mL), washed with satd. sodium bicarbonate solution (50 mL×2), water (100 mL×1), and brine (100 mL×1). The product was precipitated from DCM. In order to dissolve the precipitate, EtOAc (100 mL) was added. The combined organic layers were dried over MgSO4, filtered, and concentrated in vacuo. The residue was absorbed onto a plug of silica gel and purified by chromatography through a Redi-Sep pre-packed silica gel column (80 g), eluting with a gradient of 0% to 100% EtOAc in hexane, to provide (S)-tert-butyl 1-(5,6-difluoro-1H-benzo[d]imidazol-2-yl)ethylcarbamate (2.5025 g, 8.42 mmol, 77% yield) as orange solid. The orange solid was suspended in DCM-hexane (1:1) and filtered to give (S)-tert-butyl 1-(5,6-difluoro-1H-benzo[d]imidazol-2-yl)ethylcarbamate (2.0003 g, 6.73 mmol, 61.4% yield) as a pink solid: 1H NMR (400 MHz, DMSO-d6) δ ppm 12.34 (1H, br. s.), 7.47-7.57 (2H, m), 7.38 (1H, d, J=7.2 Hz), 4.83 (1H, quin, J=6.6 Hz), 1.45 (3H, d, J=7.0 Hz), 1.40 (9H, s); LC-MS (ESI) m/z 298.1 [M+H]+.
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