Abstract
The palladium-catalyzed Suzuki-Miyaura cross coupling reaction to forge carbon-carbon bonds fundamentally changes the practice of organic synthesis. Herein an isolated palladium catalyst supported on polymeric carbon nitride (Pd/PCN) for efficient cross coupling of bromobenzene and phenylboronic acid at room temperature is reported. It is demonstrated that the Pd/PCN catalyst with a 2 wt% Pd loading achieves the highest mole-specific activity. In addition, the size of supported Pd can strongly affect the reaction performance: the isolated Pd species exhibit higher activity compared to the Pd nanoparticles. The continuous flow tests demonstrate that the catalytic properties of the Pd/PCN catalyst strongly depend on the reaction atmosphere: Pd-catalyzed self-coupling of phenylboronic acid as a side reaction is more pronounced under an O(2) flow than in an Ar flow. Detailed mechanistic investigations through in situ infrared spectroscopy reveal the role of the base K(2)CO(3) in activating the phenylboronic acid.