CO2as both a selective agent and reaction media in palladium‐catalyzed reductive Ullmann‐type coupling reaction

Abstract Carbon dioxide as both a selective agent and reaction media in the palladium‐catalyzed Ullmann‐type coupling has been described. The results showed that aryl chlorides could be easily activated in the presence of carbon dioxide and the chemoselectivity shifted toward the palladium‐catalyzed Ullmann‐type coupling reaction. In liquid carbon dioxide, homocoupling reactions of aryl halides, including less reactive aryl chlorides, were carried out smoothly in moderate to good yields using Pd/C, zinc, and H 2 O as the catalytic system at room temperature.