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Liquid‐Crystalline Ionic Liquids as Ordered Reaction Media for the Diels–Alder Reaction
Author(s) -
Bruce Duncan W.,
Gao Yanan,
Cagia Lopes José Nuno,
Shimizu Karina,
Slattery John M.
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201602965
Subject(s) - ionic liquid , diels–alder reaction , alder , liquid crystalline , chemistry , materials science , organic chemistry , catalysis , polymer , ecology , biology
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.