title: Liquid-Crystalline Ionic Liquids as Ordered Reaction Media for the Diels-Alder Reaction.
abstract: Liquid-crystalline ionic liquids (LCILs) are ordered materials that have untapped potential to be used as reaction media for synthetic chemistry. This paper investigates the potential for the ordered structures of LCILs to influence the stereochemical outcome of the Diels-Alder reaction between cyclopentadiene and methyl acrylate. The ratio of endo- to exo-product from this reaction was monitored for a range of ionic liquids (ILs) and LCILs. Comparison of the endo:exo ratios in these reactions as a function of cation, anion and liquid crystallinity of the reaction media, allowed for the effects of liquid crystallinity to be distinguished from anion effects or cation alkyl chain length effects. These data strongly suggest that the proportion of exo-product increases as the reaction media is changed from an isotropic IL to a LCIL. A detailed molecular dynamics (MD) study suggests that this effect is related to different hydrogen bonding interactions between the reaction media and the exo- and endo-transition states in solvents with layered, smectic ordering compared to those that are isotropic.
authors.affiliation: Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK. duncan.bruce@york.ac.uk.
authors.forename: Duncan W
authors.initials: DW
authors.lastname: Bruce
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, P. R. China.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal. jnlopes@ist.utl.pt.|Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. República, 2780-157, Oeiras, Portugal. jnlopes@ist.utl.pt.
authors.forename: José Nuno
authors.initials: JN
authors.lastname: Canongia Lopes
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal.
authors.forename: Karina
authors.identifier: http://orcid.org/0000-0003-2454-1795
authors.initials: K
authors.lastname: Shimizu
authors.affiliation: Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK. john.slattery@york.ac.uk.
authors.forename: John M
authors.identifier: http://orcid.org/0000-0001-6491-8302
authors.initials: JM
authors.lastname: Slattery
keywords: Diels-Alder reaction; ionic liquids; liquid crystals; molecular dynamics simulations; ordered solvents