# Advances in Organic and Organic-Inorganic Hybrid Polymeric Supports for Catalytic Applications
## 4 Metal-Catalysed Non-Asymmetric Reactions
### C-C Coupling Reactions
The reusability of the catalyst was tested in the cross coupling of 4-chlorotoluene with phenylboronic acid. It was reused five times; a slight deactivation of catalyst was observed. The application of Pd nanoparticles supported on poly(\(N\)-vinylpyrrolidone)-grafted silica as heterogeneous catalysts for Sonogashira and Suzuki coupling reactions was also reported [78]. In detail, catalyst **134** was obtained by treatment of poly(\(N\)-vinylpyrrolidone)-grafted silica **133** with PdCl\({}_{2}\) in DMF (Scheme 48). Support **133** was afforded by reaction between acryloyl chloride and aminopropyl silica and subsequent copolymerization of the thus obtained material **132** with 1-vinyl-2-pyrrolidone in the presence of benzoyl peroxide as initiator. Catalyst **134** contained an average of 0.25 mmol-g\({}^{-1}\) of Pd. Under optimized conditions (0.5 mol % of catalyst, 2 eq. K\({}_{2}\)CO\({}_{3}\), DMF, 100 \({}^{\circ}\)C and tetrabutylammonium bromide (TBAB) only for reactions with aryl chlorides), Sonogashira-Hagihara cross-coupling reaction between phenylacetylene with different aryl halides was carried out. High yields were obtained unlike the less active 4-chloroanisole, which led to coupling product in 35% of yield. Catalyst **134** was recovered by filtration and recycled successfully for seven runs. A total Pd leaching of about 3% from the supported system after the third and sixth run was observed. Use of catalyst **134** in Suzuki coupling reaction between phenylboronic acid and different aryl halides, in the presence of K\({}_{2}\)CO\({}_{3}\) as base and DMF as solvent, provided baiyls with good yields. _Ortho-_ and _meta-_substituted aryl halides gave the corresponding products after 24 with only 30% and 40% of yield. Similar to the Sonogashira reaction, aryl chlorides gave the coupling products in the presence of TBAB. The recycling experiments for the reaction of phenylboronic acid with iodobenzene were carried out; the catalyst was used six times with no considerable leaching. [PERSON] et al. reported the first Sonogashira coupling reaction catalysed by polystyrene-supported Cu(II) complex [79]. The polystyrene-supported Cu(II) \(N\),\(N\)-dimethyl-ethylenediamine complex **136** was prepared by treatment of polymer-bound \(N\),\(N\)-dimethylethylenediamine **135** with an ethanolic solution of CuBr\({}_{2}\) at 50 \({}^{\circ}\)C (Scheme 49). Polymeric ligand **135** was synthesized by reaction between chloromethylated polystyrene and \(N\),\(N\)-dimethylethylenediamine in refluxing acetonitrile. The amount of copper incorporated into the polymer, determined by atomic absorption spectroscopy, was 0.98 mmol/g. Application of catalyst **136** in Sonogashira cross-coupling reaction between phenylacetylene and aryl iodides containing electron withdrawing or donating substituents gave  
Figure 47: Synthesis of Pd heterogeneous catalyst **131** and its application in Suzuki–Miyaura reaction. the corresponding biaryacetylenes in good yields (66%-85%). The reusability of the catalyst **136** was studied in reaction between iodobenzene and phenylacetylene. Not much decrease in the activity of catalyst was observed even after four cycles. During the course of Sonogashira coupling reactions, 0.4% of copper was lost into solution after the first run. After four recycles loss of 7% was observed. This catalyst was also applied in \(N\)-arylation of indoles [79]. In 2011, a new concept of heterogeneous materials based on highly cross-linked imidazolium salts anchored on silica gel as supports for palladium nanoparticles in high loadings was developed [80]. This topic was extended with the preparation of the material **137** as catalyst for the Heck reaction (Scheme 50) [81]. Material **137** was prepared by treatment of highly cross-linked imidazolium-based support **21a** with an aqueous solution of Na\({}_{2}\)PdCl\({}_{4}\), followed by reduction reaction with NaBH\({}_{4}\) in ethanol.