A Convoluted Polyvinylpyridine‐Palladium Catalyst for Suzuki‐Miyaura Coupling and C−H Arylation

The development of highly active and reusable supported catalysts for Suzuki‐Miyaura coupling and catalytic C−H arylation is important for fundamental and applied chemistry, with these reactions being used to produce medical compounds and functional materials. Herein, we found that a mesoporous composite made of a linear poly(4‐vinylpyridine) and tetrachloropalladate acted as a dual‐mode catalyst for a variety of cross‐coupling reactions, with both Pd nanoparticles and a Pd complex catalyst being observed under different conditions. The polyvinylpyridine‐palladium composite 1 was readily prepared via the molecular convolution of poly(4‐vinylpyridine) and sodium tetrachloropalladate to provide a hardly soluble polymer‐metal composite. The Suzuki‐Miyaura coupling and the C−H arylation of aryl chlorides and bromides with arylboronic acids, thiophenes, furans, benzene, and anisole proceeded in the presence of 0.004 mol% (40 mol ppm) to 1 mol% Pd of 1 to afford the corresponding coupling products in high yields. Furthermore, the catalyst was reused without an appreciable loss of activity. Pharmaceutical compounds and functional materials were synthesized via the coupling reactions. N 2 gas adsorption/desorption analysis indicated that the catalyst had a mesoporous nature, which played a crucial role in the catalysis. In the Suzuki‐Miyaura couplings, in situ generated palladium nanoparticles in the polymer matrix were catalytically active, while a polymeric Pd(II) complex was crucial in the C−H arylations. These catalytic species were investigated via XAFS, XPS, far‐infrared absorption, and Raman spectroscopies, as well as DFT calculations.