trans-Cinnamaldehyde is selectively hydrogenated to hydrocinnamaldehyde using a commercially available palladium catalyst in novel imidazolium ILs. The selective hydrogenation extends to benzyl cinnamate, in which the ester is protected from hydrogenolysis under similar conditions.
This invention relates to ionic liquid (ILs) solvents for chemical synthesis based on an alkyl-imidazolium cation core containing ionic liquids which have enhanced biodegradability and reduced toxicity relative to existing imidazolium bases ILs such as 1-butyl-3-methylimidazolium (bmmim) salts. Many of the described ILs produce a score of over 60% biodegradability over 28 days in a biodegradability test such as the Sturm Test, the Closed Bottle Test (OECD 301D) or the CO
2
Headspace Test (ISO 14593). The ILs of the invention comprise an alkyl substituted imidazolium cationic core having a —C═OX— side chain in the 3-position of the imidazole ring, wherein X═O, NH, N or S and an associated counteranion characterized in that the —C═OX side chain comprises at least one ether linkage. The biodegradable and non-toxic IL may be used as green solvents for the chemical, pharmaceutical, biofuel and biomass industries. The ILs of the invention are particularly useful in hydrogenation, pericyclic and metathesis reactions.
A series of imidazolium ionic liquids was prepared and screened against 7 bacterial strains. The incorporation of ether groups into the ester side-chain significantly reduced the toxicity compared with alkyl ester derivatives. Biodegradation data are also presented for 15 of the ionic liquidsâincluding 6 examples which can be classed as readily biodegradable.