To a stirred suspension of methyl 8-bromo-2-morpholino-4-oxo-4H-chromene-6-carboxylate (23 g, 62.47 mmol) in DME (300 mL) and water (30 mL) were added 1-(tert-butoxycarbonyl)-1H-pyrrol-2-ylboronic acid (14.50 g, 68.72 mmol), Na2CO3 (19.87 g, 187.41 mmol) and bis(triphenylphosphine)palladium(II) chloride (0.877 g, 1.25 mmol). The mixture was degassed with argon and heated to 80° C. for 7 h. Reaction was cooled down and concentrated, the residue was dissolved in 300 mL of DCM and 300 mL of water. The organic phase was decanted, washed with brine then dried over MgSO4, filtered and concentrated to afford a crude compound which was purified on silica, eluting with 80% AcOEt in DCM. The solvents were evaporated to afford tert-butyl 2-(6-(methoxycarbonyl)-2-morpholino-4-oxo-4H-chromen-8-yl)-1H-pyrrole-1-carboxylate (20 g, 70%) as a white powder.
