2 mmol of p-bromophenylboronic acid, 0.0456 g of 5 wt% Pd/CaCO3 (0.01 mmol of Pd), and 0.0114 g of CuI (0.03 mmol of CuI) were added to a 250 mL polytetrafluoroethylene-lined pressure vessel, followed by 10 mL of DMSO. The vessel was then assembled, and air was slowly introduced at 1.85 atm in a fume hood, followed by CO at 0.15 atm. The vessel was then placed in a 50 °C oil bath for 12 hours. After the reaction was stopped, the vessel was cooled to room temperature, and the remaining gas inside was slowly released in a fume hood.
The reaction vessel was opened, and 40 mL of 5% ammonia solution was added. The palladium catalyst was separated by filtration; this catalyst could be reused after washing and drying. The mother liquor was extracted three times with dichloromethane (30 mL), and the organic phases were combined. The organic phase was dried over anhydrous sodium sulfate, and the solvent was removed by vacuum concentration to obtain the crude product. The crude product was purified by column chromatography (using petroleum ether/ethyl acetate at a volume ratio of 20:1) to obtain 4,4'-dibromobenzophenone.
