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

• Published in: Advanced synthesis & catalysis 2020-11, Vol.362 (21), p.4687-4698
• Main Authors: Ohno, Aya, Sato, Takuma, Mase, Toshiaki, Uozumi, Yasuhiro, Yamada, Yoichi M. A.
• Format: Article
• Language: English
• Subjects: Anisole; Aromatic compounds; Benzene; Bromides; Catalysis; Catalysts; Chemical reactions; Convolution; Coupling (molecular); Couplings; Cross coupling; C−H Arylation; Functional materials; Furans; Infrared absorption; Medical materials; Molecular Convolution; Nanoparticles; Palladium; poly(4-vinylpyridine); Polymeric Palladium; Polyvinyl pyridine; Suzuki-Miyaura coupling; Thiophenes; X ray photoelectron spectroscopy
• ISSN: 1615-4150; 1615-4169
• DOI: 10.1002/adsc.202000742

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. N2 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.