Solvent effects on the mechanism and selectivities of asymmetric Diels-Alder reactions

Abstract

The electrostatic effect of the solvent on the reaction of cyclopentadiene with methyl acrylate has been studied with the help of a Self-Consistent Reaction Field model by means of ab initio computations. The effect on the reaction mechanism, endo/exo selectivity, and activation energy has been analyzed. Moreover, the computations allow a discussion of the solvent effect on the diastereofacial selectivity when chiral acrylates are used and a comparison with experimental data for the reaction of cyclopentadiene with (-)-menthyl acrylate. The results are in agreement with the experimentally observed increase of the endo/exo and diastereofacial selectivities as a function of solvent polarity, but hydrophobic effects and hydrogen-bond formation are necessary to account for changes in reaction rates.