To a stirred solution of 8-bromo-7-fluoro-4,6-dimethylbenzo[c][2,7]naphthyridin-5(6H)-one (350 mg, 1.090 mmol) and tert-butyl (1-hydroxy-2,4-dimethylpentan-2-yl)carbamate (504 mg, 2.180 mmol) in toluene (10 mL) was added cesium carbonate (355 mg, 1.09 mmol) and 2-Di-t-butylphosphino-2′,4′,6′-tri-i-propyl-1,1′-biphenyl (28 mg, 0.065 mmol). The reaction mixture was degassed with argon for 5 min and then palladium acetate (7.34 mg, 0.033 mmol) was added to it. The reaction mixture was heated to 100° C. for 18 h. Then, it was filtered through diatomaceous earth (Celite®) and the filtrate was evaporated to afford tert-butyl (1-((7-fluoro-4,6-dimethyl-5-oxo-5,6-dihydrobenzo[c][2,7]naphthyridin-8-yl)oxy)-2,4-dimethylpentan-2-yl)carbamate which was taken to next step without purification. LC/MS (ESI) m/e 472.2 [(M+H)+, calcd for C26H35FN3O4 472.2]; LC/MS retention time (method C): tR=2.17 min.
