Diels-Alder cycloaddition versus ring-opening esterification: Acomputational study of the mechanism of formation of oxa-norbonenelactones from the reaction of furfuryl alcohol and itaconic anhydride
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Date
2018
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Elsevier B.V.
Abstract
The reactions of furfuryl alcohol with itaconic anhydride can proceedviafour plausible pathways–two path-ways involving initial Diels-Alder cycloaddition followed by lactonization and two pathways involving initialesterification followed by intramolecular Diels-Alder cycloaddition–to afford two distinct norbornene productsbearing either afive- or six-membered butyrolactone ring respectively. DFT calculations reported herein showthat thefirst-step Diels-Alder cycloaddition reactions have barriers of 8.5 and 11.8 kcal/mol which are far lowerthan the barriers of 29.6 and 36.9 kcal/mol for the esterification pathways. The calculated energies for theexperimentally observedfive- and six membered oxa-norbornene lactone isomers are exergonic with reactionenergies of−17.1 and−12.8 kcal/mol respectively. Thermodynamically thefive-membered isomer is morestable adduct than the six-membered adduct. Thus the most preferred pathway is the one involving initial[4 + 2] cycloaddition followed by lactonization to form thefive-membered butylrolactone ring. Substitution ofmethyl groups on the carbon bearing the hydroxyl group shows that the substituents do not affects the reactionpathways markedly.
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An article published by Elsevier B.V. and also available at https://doi.org/10.1016/j.comptc.2018.05.019
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Citation
E. Fosu et al. Diels-Alder cycloaddition versus ring-opening esterification: Acomputational study of the mechanism of formation of oxa-norbonenelactones from the reaction of furfuryl alcohol and itaconic anhydride, https://doi.org/10.1016/j.comptc.2018.05.019