Alkylammonium ionic liquids as solvents for Diels-Alder reactions have shown higher endo to exo stereoisomer ratios of the products compared to common organic solvents.  GC-MS and 1H NMR analysis were used to determine the isomer ratios of the products in ethylammonium nitrate, propylammonium nitrate, and tributylammonium nitrate as well as de-ionized water as a reference.  Cyclopentadiene was used as the diene for all the Diels-Alder reactions with various dienophiles including acrylic acid, methyl acrylate, methyl vinyl ketone, 1-hexene, and styrene to examine the effects of steric hindrance and electronics on the reactions and to compare to literature results.  The polarity of the solvents was determined using solvatochromatic dyes to define a relationship between the endo to exo ratio and the polarity of the solvent.  It was found that there is a direct correlation with solvent polarity and the endo to exo ratio of the corresponding Diels-Alder products.

Stereoselectivity of Diels-Alder reactions in protic ionic liquids

244th National Meeting (2012)

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