1,2-Dichloroethane → (5-{3-[(5-Bromo-pyridine-2-carbonyl)-amino]-phenyl}-5-fluoromethyl-5,6-dihydro-2H-[1,4]oxazin-3-yl)-carbamic acid tert-butyl ester

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A solution of [5-(3-azido-phenyl)-5-fluoromethyl-5,6-dihydro-2H-[1,4]oxazin-3-yl]-carbamic acid tert-butyl ester (56 mg, 0.161 mmol) in 2 ml of EtOAc was hydrogenated in the presence of Lindlar catalyst (11 mg) for 3 h. The mixture was filtered through Celite, and the filtrate was evaporated. The crude [5-(3-amino-phenyl)-5-fluoromethyl-5,6-dihydro-2H-[1,4]oxazin-3-yl]-carbamic acid tert-butyl ester (50 mg, 0.155 mmol) was taken up in 2 ml of dichloromethane. A mixture of 5-bromo-pyridine-2-carboxylic acid (34.4 mg, 0.170 mmol), HOBT (30.9 mg, 0.17 mmol) and EDC (32.6 mg, 0.17 mmol) in 2 ml of dichloromethane was added, followed by the addition of triethylamine (0.054 ml). The mixture was stirred for 4 h, treated with 5% aqueous NaHCO3 solution and extracted twice with dichloromethane. The organic phase was dried with MgSO4 and evaporated. The residue was chromatographed on silica gel (EtOAc/cyclohexane=1:4) to yield the title compound. TLC (hexane/EtOAc=3:1): Rf=0.16; HPLC: RtH1=2.763 min; 1H-NMR (400 MHz, CDCl3): 9.80 (br, 0.1H), 8.60 (d, 1H), 8.11 (d, 1H), 7.98 (d, 1H), 7.77 (br, 1H), 7.73 (d, 1H), 7.33 (br, 1H), 7.15 (d, 1H), 4.75-3.65 (m, 6H), 1.60 (br; minor rotamer tBu), 1.42 (br; major rotamer tBu); MS: 507, 509 [(M+H)+].

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