A 25-mL single-neck round-bottomed flask equipped with a magnetic stirrer and a reflux condenser was charged with 257a (203 mg, 0.50 mmol), {3-[(acetoxy)methyl]-2-{4,4-dimethyl-9-oxo-1,10-diazatricyclo[6.4.0.02,6]dodeca-2(6),7-dien-10-yl}pyridin-4-yl}boronic acid 199e (640 mg, 1.6 mmol), K3PO4 (212 mg, 1.0 mmol), 1,1′-bis(diphenylphosphino)ferrocenedichloropalladium(II) (18 mg, 0.025 mmol), sodium acetate (82 mg, 1.0 mmol), acetonitrile (10 mL), and water (0.2 mL). After three cycles of vacuum/argon flush, the mixture was heated at 100° C. for 2.5 h. Analysis of the reaction mixture by LCMS showed complete conversion to the desired product. The reaction mixture was cooled to room temperature and concentrated under reduced pressure. The residue was diluted with dichloromethane (20 mL) and water (20 mL). The aqueous layer was separated and extracted with dichloromethane (3×20 mL). The combined organic layer was dried over Na2SO4 and filtered. The filtrate was concentrated under reduced pressure. The dark residue was purified by silica-gel column chromatography eluting with 60:1 dichloromethane/methanol to afford 257b (160 mg, 47%) as black solid. MS-ESI: [M+H]+ 680.1
