A mixture of 8-bromo-3-(4-fluorophenyl)-imidazo[1,5-a]pyridine (355 mg, 1.22 mmol), Et3N (330 μL, 2.5 mmol), Pd[PhCN]2Cl2 (11 mg, 0.029 mmol), and 1,1-bis(diphenylphosphino)ferrocene (dppf) (42 mg, 0.076 mmol) in absolute ethanol (15 mL) is placed in a pressure reactor with stirring and placed under 15 bars of carbon monoxide and warmed at 140° C. After 4 hours, the pressure reactor is cooled to room temperature, returned to atmospheric pressure and opened. The reaction mixture is concentrated in vacuo, the resulting residue is dissolved in dichloromethane and passed through a pad of silica gel eluting with ethyl ether to afford 3-(4-fluorophenyl)-imidazo[1,5-a]pyridine-8-carboxylic acid ethyl ester.
