{1-[4-(8-Bromo-4-oxo-2-phenyl-4H-chromen-3-yl)-phenyl]-cyclobutyl}-carbamic acid tert-butyl ester (200 mg, 0.367 mmol), and [1,1′-bis(diphenylphosphino)-ferrocene]dischloropalladium(II) complex with dichloromethane (60 mg, 0.073 mmol) were loaded into a microwave vial. The vial was sealed and a solution of triethylamine (0.102 mL, 0.732 mmol) in MeOH (4 mL) was added. The vial was evacuated and flushed twice with argon, followed by carbon monoxide. The reaction mixture was heated conventionally at 50° C. under an atmosphere of carbon monoxide for 18 h. The reaction mixture was allowed to cool to RT and was concentrated in vacuo. The resultant residue was subjected to flash chromatography (SiO2, gradient 0 to 10% EtOAc in DCM) to give the title compound as a gum (193 mg, 100%). LCMS (Method G): RT=4.41 min, [M+H]+=526.
