Studies On The Applications Of Ionic Liquids In Catalytic Reactions

The applications of ionic liquids in catalytic reactions as Michaeladdition and Fischer indole synthesis were studied in this dissertation.First, base-catalyzed Michael additions of malonates toα,β-unsaturated ketones andβ-nitroolefins were performed inimidazolium-type ionic liquids. In the presence of NaOH, 75.2～96.8ï¼…yields of Michael adducts were offered after 45～120min at roomtemperature with BMImPF₆ as reaction medium. The NaOH/BMImPF₆system could be recycled and reused for at least six times without muchloss in activities.Secondly, a novel one-pot Fischer indole synthesis approach hasbeen developed using Bronsted acidic ionic liquids as dualsolvent-catalysts. 83～97ï¼…yields were obtained after reaction inBMImHSO₄ at 70～110℃in 0.5～6h, and exclusive formation of2,3-disubstituted indoles was observed in the reaction of alkyl methyl unsymmetrical ketones. The indoles produced could be convenientlyseparated from the reaction mixture without any volatile organic solvents,and the BMImHSO₄ could be readily reused without efficient loss aftersimple treatment involving only 1 equiv.-HC1 neutralization and filtration.Finally, a novel series of ionic liquids, comprising imidazoliumcations with amide- functionalized groups on the alkyl side-chain havebeen prepared from readily available starting materials with 51.8～74.0ï¼…total yields. Their structures were characterized with ¹H NMR, IR andelemental analysis. DSC, TG, viscosity, solubility and electrochemistrydetermination results showed that these ionic liquids have high thermalstability(undecomposable below 295.2℃), good solubility in traditionalpolar solvents, large electrochemical window(4.0～4.2V), and someexhibit very low freezing points as below to -76.5℃—a highly valuableproperty in many applications. The application of theamide-functionalized ionic liquid 3-methyl-1-(N,N-diethylcarbamoylmethyl)-imidazolium tetrafluoroborate (3a) as reaction media in the Michaeladdition reaction and Fischer Indole synthesis afforded 0.8～6.0ï¼…yieldsand 21.4～74.4ï¼…conversions improved compared with those by usingtraditional ionic liquids.