# Advances in Organic and Organic-Inorganic Hybrid Polymeric Supports for Catalytic Applications
## 4 Metal-Catalysed Non-Asymmetric Reactions
### C-C Coupling Reactions
In presence of less reactive aryl chlorides, relatively low yields (24%-34%) were obtained even when the reactions were carried out at a higher temperature (120 \({}^{\circ}\)C), over a longer reaction time and with a higher catalyst loading (0.05 g instead of 0.01 g for 1 mmol of halide). The Sonogashira coupling between benzyne and aryl bromides or aryl iodides at 120 \({}^{\circ}\)C gave the corresponding biaylacetylenes in high yields (93%-99%)without Cul co-catalyst. In the case of Heck coupling, catalyst **147** again exhibited very high activity and selectivity, converting aryl iodides and bromides with high yields (97%-99%). In all reactions, material **147** was more active than the corresponding Pd-based homogeneous catalyst used under the same conditions. Furthermore, the catalyst was found to be recyclable. It was used for five recycling trials without significant loss of the catalytic activity and leaching of Pd. According authors, this result might be reasonably attributed to the strong coordination between the Pd species and the phenanthroline moieties. Halloysite, a double-layered aluminosilicate mineral that has a predominantly hollow tubular structure, has been also used as support for ionic liquid (IL) phase-based materials. External surface functionalization of halloysite nanotubes (HNTs) with ILs was achieved through grafting of 3-mercaptoethanolpropyl trimethoxysilane by microwave irradiation, followed by anchorage of 3-octyl-1-vinylimidazolium bromide via thiol-ene reaction (Scheme 56) [90; 91]. MW irradiation allowed obtaining high loading onto the HNTs surface compared to those obtained through conventional synthesis. Treatment with Na\({}_{2}\)PdCl\({}_{4}\) in water followed by reduction with NaBH\({}_{4}\) gave the Pd-based catalyst **149**. This latter was used in Suzuki reactions between phenylboronic acid and several aryl halides in ethanol/water with a catalytic loading of 1.0 or 0.1 mol %. Reactions were carried out under MW irradiation at 120 \({}^{\circ}\)C for 10 min to give the corresponding biphenyls in good to excellent yields. Up to five cycles were performed using catalyst **149** at 1.0 mol % loading. In addition, the Pd-based halloysite-bis-triazolium salt **152** was prepared. In this case, the starting material was the azido-functionalized HNTs **150**. The HNTs modified with the bis-triazolium salt were obtained using the bis-alkyne **151** and a reactions sequence based on two click reactions, first with the azido-HNT **150**, then with NaN\({}_{3}\), followed by quaternization with 1-bromobutane (Scheme 57) [92]. Palladium was immobilized from Na\({}_{2}\)PdCl\({}_{4}\) solution followed by reduction. Catalyst **152** was used (0.1 mol %) in the Suzuki-Miyaura reaction between phenylboronic acid and a set of aryl halides in water at 120 \({}^{\circ}\)C in the presence of K\({}_{2}\)CO\({}_{3}\) as base. All the reactions were run for 10 min under MW irradiation. High conversions were obtained with anisole derivatives, lower yields with other substrates but an increasing in their conversion was achieved carrying out a reaction in mixture water/ethanol (1:1). Recycling of catalyst was investigated by the reaction between phenylboronic acid and 3-bromoanisole. Catalyst was recovered by centrifugation and reused in the same reaction in five cycles. Biphenyl-3-anisole was afforded in 99%-90% for five cycles. In 2015, the synthesis of highly-functionalized biparls via Suzuki-Miyaura cross-coupling catalyzed by Pd nanoparticles supported on the amino-functionalized mesoporous metal-organic framework MIL-101-NH\({}_{2}\) (**Pd-MIL-101-NH\({}_{2}\)**, see Scheme 58) was proposed [93]. This catalytic system with a palladium loading of 8 wt % was known to have the optimal amount of palladium impregnated in MIL-101-NH\({}_{2}\)[94,95] for this type of applications [96]. In presence of 1 mol % of **Pd-MIL-101-NH\({}_{2}\)**, the coupling of boronic acids or pinacolate esters with heteroaryl iodides and bromides was investigated.