To a stirred suspension of 8-chloro-9-fluoro-6-methylbenzo[c][2,7]naphthyridin-5(6H)-one (40 mg, 0.152 mmol), (S)-tert-butyl (1-hydroxy-4-methylpentan-2-yl)carbamate (39.7 mg, 0.183 mmol), di-tert-butyl(2′,4′,6′-triisopropyl-[1′,1′-biphenyl]-2-yl)phosphine (38.8 mg, 0.091 mmol) and cesium carbonate (74.4 mg, 0.228 mmol) in toluene (4 mL) was added palladium(II)acetate (10.26 mg, 0.046 mmol). Nitrogen gas was bubbled through the mixture for 5 min, and then the reaction mixture was heated to 85° C. for 8 h. The reaction mixture was cooled to room temperature and diluted with ethyl acetate (2 mL) and filtered through diatomaceous earth (Celite®). The filtrate was washed with water (2×2 mL) and brine (2×2 mL), dried over sodium sulfate and concentrated under reduced pressure. The residue was purified via silica gel column chromatography (60% ethyl acetate in hexanes) to afford (S)-tert-butyl (1-((9-fluoro-6-methyl-5-oxo-5,6-dihydrobenzo[c][2,7]naphthyridin-8-yl)oxy)-4-methylpentan-2-yl)carbamate (28 mg, 0.023 mmol, 15% yield). LC/MS (ESI) m/e 444.2 [(M+H)+, calcd for C24H31lFN3O4 444.2]; LC/MS retention time (method A): tR=2.02 min.
