# Advances in Organic and Organic-Inorganic Hybrid Polymeric Supports for Catalytic Applications
## 4 Metal-Catalysed Non-Asymmetric Reactions
### C-C Coupling Reactions  
In 2014, the self-supported oximepalladacycle **127** was synthesized by using a polymeric ligand based on the polyether ether ketone architecture and employed as pre-catalyst in Suzuki-Miyaura reactions (Scheme 45) [75]. In detail, the self-supported oximepalladacycle **127** was prepared in three synthetic steps: (a) copolymerization of 4,4'-dihydroxybenzophenone with 1,12-dibromododecane to afford **125**; (b) conversion of ketone groups into oximes in order to obtain **126**; and (c) cyclization in the presence of Li\({}_{2}\)PdCl\({}_{4}\). The Pd loading level was 0.77 mmol/g. Use of **127** as pre-catalyst in the Suzuki-Miyaura reactions between aryl bromides and phenylboronic acid at 80 \({}^{\circ}\)C led to biphenyl products with excellent yields (96%-99%) in short reaction times. Higher temperatures and longer times were needed for the reactions with aryl chlorides; only with activated aryl chlorides biphenyl products were obtained in moderate yields (42%-65%). The recyclability of **127** was studied. Catalyst **127** was recovered by filtration, after having cooled the reaction mixture to room temperature and added ether and water to facilitate its precipitation. It was reused up to four times giving excellent yields with low levels of Pd leaching. In the same year, cross-linked polyallylamine polymer-supported aminopyridylphosphine palladium(II) complexes were prepared and used as heterogeneous catalysts for Suzuki-Miyaura and Heck cross coupling reactions [76]. These new materials, **130a** and **130b**, were synthesized as depicted in Scheme 46. First, the cross-linked polyallylamine polymer **128** was prepared by copolymerization of polyallyamine hydrochloride salt with epichlorohydrin under basic conditions and successive ion exchange with sodium hydrogen carbonate. Then, the amino-groups of **128** were functionalized by 6-(diphenylphosphino) picolinaldehyde or 2-(diphenylphosphino)benzaldehyde to form cross-linked polyallylamine polymer-supported phosphine-Schiff bases **129a** or **129b** respectively. Finally, the complexation of **129a** and **129b** with Pd led to materials **130a** and **130b** (Pd loading **130b**: 0.57 mmol/g; Pd loading **130a**: and 0.5 mmol/g). The catalytic activity of **130a** and **130b** was compared in the coupling of bromobenzene with phenylboronic acid under optimized conditions (dioxane, K\({}_{2}\)CO\({}_{3}\), 0.05 mol % of catalyst, reflux). Catalyst **130a** was found to be more efficient than catalyst **130b**. Catalyst **130a** was also employed in Suzuki reaction between different aryl halides and substituted phenylboronic acids. High yields were obtained with aryl iodides and bromides (90%-99%). Low to high yields with aryl chlorides (35%-95%) were obtained. The reaction between 4-amino-1-chlorobenzene and phenylboronic acid only gave 35% of desired product, while the reaction between 4-chloronitrobenzene and 4-methoxyphenylboronic gave better result (yield 95%). The use of catalyst **130a** in Heck reaction of aryl halides with terminal olefins also gave good yields (68%-95%). Recycling experiments were carried out for the cross-coupling of bromobenzene and phenylboronic acid. The catalyst was recovered by filtration and reused at least five times without significant loss of activity. Recently, triphenylphosphine ligand and palladium nanoparticles were immobilized in situ in a polymer synthesized by palladium catalysed Suzuki-Miyaura reaction between tris(4-bromophenyl)amine and benzene-1,4-diboronic acid, to which tris(4-chlorophenyl) phosphine participated [77]. The optimization of this procedure by using Pd\({}_{2}\)(dba)\({}_{3}\) led to Pd heterogeneous catalyst **131** (Scheme 47). The amount of Pd in the catalyst, determined by ICP-AES, was 1.81 wt %. Application of catalyst **131** in Suzuki-Miyaura reaction of aryl chlorides and bromides with aryl boronic acids allowed to obtain the corresponding biphenyl compounds in good to excellent yields (70%-99%).