Solvent Effects on the Stereoselectivity of Reaction of Methyl Acrylate, Methyl Methacrylate and Methyl trans-Crotonate with Cyclopentadiene: A Computational Study*

The stereoselectivity of reaction of methyl acrylate, methyl methacrylate and methyl transcrotonate with cyclopentadiene was studied with ab initio RHF/6-31G* and B3LYP/6-31G* levels of theory. The stereoselectivities predicted for methyl acrylate and methyl methacrylate with cyclopentadiene in the gas phase were found to be in good agreement with experimental results. The preference of endo selectivity in solvents was more pronounced for methyl acrylate, however, the preference for the exo-addition for methyl methacrylate was predicted to be reduced in solvents. The solvent calculations predicted the endopreference for methyl trans-crotonate in agreement with the experimental observations. The lower endo selectivity for methyl trans-crotonate with cyclopentadiene seems to be governed by the degree of asynchronicity of endoand exo-transition states in water. B3LYP/6-31G* calculated activation enthalpy was found to be in good agreement with the observed activation enthalpy for methyl acrylate and cyclopentadiene, however, this method does not predict the stereoselectivities correctly in all cases. The hydrogen bonding between water and polarized transition states seems to be important for rate acceleration in water