To a mixture of ethyl 3-(4-chloro-2-fluorophenyl)-1H-pyrrole-2-carboxylate (2.00 g, 7.47 mmol), K2HPO4 (3.90 g, 22.4 mmol) and dichlortris(1,10-phenanthroline)-ruthenium(II) hydrate (106 mg, 0.149 mmol) in argon degassed dry MeCN (24 mL) was added CF3SO2Cl (1.59 mL, 14.9 mmol). The reaction mixture was stirred for 18 h at a temperature of 25-30° C. adjacent to a fluorescent light bulb (E27-32W, 4000K, 65 mA). The reaction mixture was diluted with argon degassed dry MeCN (24 mL). Extra reagents were added: CF3SO2Cl (398 μL, 3.73 mmol) and dichlortris(1,10-phenanthroline)-ruthenium(II) hydrate (106 mg, 0.149 mmol). The reaction mixture was stirred for 3 d at a temperature of 25-30° C. adjacent to a fluorescent light bulb. Subsequently, EtOAc (100 mL) and H2O (100 mL) were added. The aqueous layer was extracted with EtOAc (50 mL). The combination of organic layers was washed with saturated aqueous NaHCO3 and with brine, dried (Na2SO4) and the solvent was evaporated. The crude product was purified by flash chromatography (silica, gradient heptane/EtOAc, 1:0→4:1) to give a yellow solid, which was crystallised from hot heptane to provide 1.01 g (40%) of the desired product as colourless crystals.
