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

Abstract

The development of highly active and reusable supported catalysts for Suzuki-Miyaura coupling and catalytic CÀ 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 CÀ 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 CÀ H arylations. These catalytic species were investigated via XAFS, XPS, far-infrared absorption, and Raman spectroscopies, as well as DFT calculations.

Heterogenization of a Molecular Ni Catalyst within a Porous Macroligand for the Direct C–H Arylation of Heteroarenes

“…While proof-of-concept heterogeneous C–H activation catalysts were recently published by the group of Yamada for palladium-catalyzed thiophene arylation and by the group of Sawamura for nickel-catalyzed benzoxazole arylation, a general protocol is still missing.…”

“…27 Furthermore, POP-type materials were already reported for the immobilization of nickel catalyst for the ethylene oligomerization, 34 or for Suzuki-Miyaura coupling. 35 While proof-of-concept heterogeneous C−H activation catalysts were recently published by the group of Yamada for palladium-catalyzed thiophene arylation 36 and by the group of Sawamura for nickel-catalyzed benzoxazole arylation, 37 a general protocol is still missing.…”

Polymer-Supported-Cobalt-Catalyzed Regioselective Cyclotrimerization of Aryl Alkynes

“…Because steric repulsion between a bulky ligand and an aryl acetylene could suppress the formation of 1,2,4-triarylbenzene, , we assumed that a polymer-supported catalyst might generate the desired 1,3,5-triarylbenzenes with very high selectivity. Polymers like poly­(4-vinylpyridine) (P4VP) are advantageous because in addition to being bulky, they enable heterogeneous catalysis − and thus catalyst reuse. Although homogeneous cobalt catalysis for cyclotrimerization has been reported, − to the best of our knowledge, polymer-supported cobalt − has not yet been applied to this reaction.…”

Switching from Biaryl Formation to Amidation with Convoluted Polymeric Nickel Catalysis

“…Owing to the higher lability of nickel to ligands, heterogeneous nickel catalysts are unstable and readily decomposed, and therefore, the development of highly active, reusable, and bench-stable heterogeneous nickel catalysts is challenging. We reported a methodology for the preparation of highly active and reusable polymeric palladium and copper catalysts, also known as the molecular convolution methodology . Considering the lack of metal leaching, high activity, and reusability of the nickel catalysts developed with this approach, this methodology was applied to the development of polymeric nickel catalysts.…”

“…Therefore, we explored the possibility for switchable selectivity between Suzuki–Miyaura-type coupling and amidation depending on the presence or absence of amides. Herein, we report switchable selectivity from biaryl formation to amidation, promoted by a heterogeneous, bench-stable, reusable, and convoluted polymeric nickel catalyst, poly­(4-vinylpyridine) (P4VP)-NiCl 2 polymer.…”