Development of Titanium Dioxide-Supported Pd Catalysts for Ligand-Free Suzuki–Miyaura Coupling of Aryl Chlorides

Catalysts

Masatoshi Yoshimura¹  Yukio Takagi¹  Yutaka Ohya²  Hayato Masuda³  Yoshinari Sawama³  Naoya Ito³  Tomohiro Ichikawa³  Takumu Tachikawa³  Hironao Sajiki³  Tsuyoshi Yamada³  Kwihwan Park³ 

[1] Catalysts Development Center, N.E. Chemcat Corporation, 678 Ipponmatsu, Numazu 410–0314, Japan;Department of Chemistry and Biomolecular Science, Gifu University, 1-1 Yanagido, Gifu 501–1193, Japan;Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu 501–1196, Japan;

关键词: Suzuki–Miyaura reaction;    palladium;    heterogeneous catalyst;    titanium oxide;    anatase titania;    aromatic chloride;   

DOI  :  10.3390/catal9050461

来源: DOAJ

【 摘 要 】

The catalyst activities of various heterogeneous palladium catalysts supported by anatase-, rutile- and brookite-type titanium oxide for ligand-free Suzuki−Miyaura cross-coupling reactions of aryl chlorides were evaluated. Palladium acetate [Pd(OAc)₂], supported on anatase-type titanium oxide (TiO₂) via acetonitrile solution impregnation process without reduction [Pd/TiO₂ (anatase-type)], demonstrated the highest catalyst activity in comparison to those of other titanium oxide (rutile- or brookite-type) supported Pd(OAc)₂ without reduction and reduced Pd/TiO₂ (anatase-type) [Pd(red)/TiO₂ (anatase-type)]. Various aryl chloride and bromide derivatives were smoothly coupled with arylboronic acids including heteroarylboronic acids in the presence of 5−10 mol% Pd/TiO₂ (anatase-type) without the addition of any ligands. Although the fresh Pd/TiO₂ (anatase-type) catalyst was surprisingly comprised of ca. 1:2 mixture of palladium(II) and palladium(0) species according to X-ray photoelectron spectroscopy (XPS), in spite of no reduction process, significant further increment of palladium(0) species was observed during the Suzuki−Miyaura coupling reaction, and Pd/TiO₂ (anatase-type) was converted into a catalyst, which contained palladium(0) species as the main component [ca. 1:5 mixture of palladium(II) and palladium(0) species]. Therefore, the reduction via the electron donation process to the palladium(II) species may have occurred during the reaction on anatase-type titanium oxide.

【 授权许可】

Unknown