# Advances in Organic and Organic-Inorganic Hybrid Polymeric Supports for Catalytic Applications
## 4 Metal-Catalysed Non-Asymmetric Reactions
### Epoxidation of Alkenes
Catalysts **114e-g** were synthesized by copolymerization of o-POSS with imidazole ionic liquids bearing different alkyl chains (C\({}_{4}\)H\({}_{9}\), C\({}_{12}\)H\({}_{25}\), C\({}_{16}\)H\({}_{33}\)) keeping the molar ratio IL:o-POSS 8:1 and carrying out the ion-exchange in the same way. The optimum specific surface (25.0 m\({}^{2}\)/g) and pore volume (0.175 cm\({}^{3}\)/g) were obtained with **114b**. The catalytic performances of various catalysts were assessed in the epoxidation of cyclootene with aqueous H\({}_{2}\)O\({}_{2}\) as oxidant and acetonitrile as solvent. All catalysts of series showed high conversions (81%->99%) and selectivity (>99%). Catalyst **114b** was also employed in epoxidation of various alkenes obtaining good to excellent conversions (51%->99%) and selectivity (66%-100%). The catalytic reusability of **114b** was evaluated in the epoxidation of cyclootene. The catalyst was recovered by filtration and then reused for four runs without observing loss in catalytic activity. [PERSON] et al. also reported an effective hybrid catalyst based on polyoxometalate and polymer [68]. This new catalyst, denoted as **115**, was constituted by the linear positively charged polymer, poly(dimethyl diallyl) ammonium, and the polyoxometalate[\(\gamma\)-1,2-H\({}_{2}\)SiV\({}_{2}\)W\({}_{10}\)O\({}_{40}\)]\({}^{4-}\) (Scheme 40). Catalyst **115** was used in the epoxidation of various allylic alcohols using only one equivalent of hydrogen peroxide in water under mild reaction conditions. _trans_-2-Hexen-1-ol, _cis_-2-penten-1-ol and crolyl alcohol were oxidized to the corresponding epoxides in high yields (79%-88%). Poor reactivity  
Figure 39: Synthesis of POSS-derived mesostructural and amphiphilic copolymer-polyoxometalate catalysts **114a-g** and their application in the epoxidation of alkenes. was showed for the oxidation of 2-methyl-2-propen-1-ol (38% yield). Catalyst **115** could be recovered and reused. An emulsion was formed when the catalyst was dispersed in an aqueous reaction system. After the reaction, the organic products were separated from the aqueous phase by extraction with ethyl acetate and the catalyst, remained in the aqueous solution as stable emulsion, could be used for the next run. The reuse of the catalyst for epoxidation of croptyl alcohol was reported; after three consecutive reuses, there was no significant loss of initial catalytic activity. This catalyst was also used in heterogeneous oxidation of sulfides with good results [67]. A wide range of polymer-supported Mo(VI) complexes have been successfully employed as catalysts for alkene epoxidation over the last few decades [69]. In 2014, the synthesis and application of the polymer-supported diimine molybdenum carbonyl complexes pre-catalysts **118a-b** (Scheme 41) were described [70]. Molybdenum hexacarbonyl was immobilized onto polystyrene-diimines **117a** and **117b**, that were produced by functionalization of aldehyde polystyrene with ethylene diamine and successive reaction with benzaldehyde or 4-nitrobenzaldehyde. Tetracarbonyl coordination of the supported ligands with the molybdenum carbonyl, the pentacarbonyl and tri-carbonyl coordination of them were assumed. Resins **118a-b** were used in the epoxidation of different alkenes under optimized conditions (_tert_-butyl hydroperoxide -TBHP- as oxidant and CCl\({}_{4}\) as solvent), showing to be active and selective. Conversions and selectivities obtained with **118a** were in the 32%-94% and 69%-100% range, respectively, while those obtained with **118b** in the 48%-100% and 80%-100% range, respectively. The reusability of pre-catalysts **118a** and **118b** was investigated in epoxidation of cyclootene; the pre-catalysts were reused six times without any loss of their initial activities. **Scheme 41. Polymer-supported diimine molybdenum carbonyl complexes **118a-b** as pre-catalysts for alkene oxidation.