# Advances in Organic and Organic-Inorganic Hybrid Polymeric Supports for Catalytic Applications
## 2 Organocatalysed Non-Asymmetric Reactions
### Synthesis of Cyclic Carbonates  
[PERSON] et al. reported the synthesis of a series of urethane-based poly(ionic liquid)s (PILs) and their application as catalysts in the cycloaddition of CO\({}_{2}\) to propylene oxide [15]. Urethane-based PILs were synthesized by addition of hexamethylenediisocyanate to dimethylolbutanoic acid and poly-(tetramethylene ether) glycol (PTMG Mn = 1000 or 2000 g/mol), and subsequent exchange reaction with 1-butyl-3-methylimidazolium chloride (Scheme 7). In addition to **14a**, without chain extension, different urethane-based PILs with chain extension **14b**, **15a**, **15b** and **15c** were prepared by adding diethanolamine (for **14b** and **15a**), hydrazine (for **15b**) and ethylenediamine (for **15c**) as chain extenders, and by varying the molecular weight of the polyol. Variation of compositions of PILs influenced their thermal and physical properties as well as their catalytic activity. The PILs with superior Mn (PTMG 2000) and higher chain extender length (**15a** and **15c**) exhibited higher activity. In fact, the chain extension improved the mobility of the PILs favouring the diffusion and solubility of CO\({}_{2}\) in material, thus increasing its interaction with the active sites. These results were similar to those obtained with 1-butyl-3-methylimidazolium chloride in the same conditions (conversion 84%).The authors proposed a possible mechanism that clarified the role of the imidazolium cation and the nucleophilic group COO\({}^{-}\). After each reaction, the urethane-based PILs were recovered and reused up to five times without a significant loss of its catalytic activity. Figure 6: Synthesis of sulfonic acid-functionalized polymer **13** and its use as catalyst in Beckmann rearrangement. [PERSON] et al. developed a systematic approach to understand the relation between structure of porous PILs and their properties, by testing a set of porous PILs as catalysts in the coupling reaction between CO\({}_{2}\) and ethylene oxide under very mild conditions (room temperature and low pressure) by means of in-situ FTIR spectroscopy within 14 h of reaction [16]. In this regard, the series of porous PILs, **16a-d** and **17a-d** (Scheme 8), were prepared through alkylation of non-ionic co-polymers **16-17** synthesized by a precipitation polymerization method using vinylimidazole (VIm) as functional monomer and DVB as cross-linking agent. Polymers **16** and **17** were obtained at volume ratio of DVB:VIm of 5:5 and 3:7, respectively. The effect of the counter anion (I\({}^{-}\), Br\({}^{-}\) and BF\({}_{4}\)\({}^{-}\)), the length of the alkyl chain (methyl and butyl) and the cross-link degree were investigated. The catalytic performances of PILs depended on the presence of a sufficient surface area and were proportional to the VIm content. The catalyst activity increased with increasing the nucleophilicity of the anion (I\({}^{-}\) > Br\({}^{-}\)) and length of alkyl chains, that stabilized the imidazole cation and reduced the electrostatic attraction between the ion-pair, so that the anion was more available to catalyse the reaction. PILs with BF\({}_{4}\)\({}^{-}\) showed no activity due to the low nucleophilicity of BF\({}_{4}\)\({}^{-}\) anion, whose high delocalized charge was not sufficient to allow the ring opening of ethylene oxide. Non-ionic co-polymers **16-17** showed very low activity. Finally, the catalytic activity of Poly(mVm\({}^{+}\)I\({}^{-}\)) was very low, despite the higher concentration of active sites, as a consequence of the absence of porosity and then of the low accessibility to the active sites. In 2014, a series of multilayered covalently-supported ionic liquid phase (mlc-SILP) materials **18**, **19a-b**, **20a-b**, **21a-b** were synthesised by grafting different bis-vinylimidazolium salts on thiol-functionalised silica (Scheme 9) [17]. Covalently-supported imidazolium salts represent an interesting class of recyclable catalysts with excellent stability and durability [18,19].