AnAb InitioMolecular Orbital Study on the Ene Reaction of Methyl Acrylate with Propene

The exo and endo transition structures for the ene reaction of methyl acrylate with propene have been located with RHF calculations at the 3-21G and 6-31G levels. Energetics have been evaluated with the 6-31G* basis set and MP2 correlation energy correction. The transition-state geometries and the calculated energetics have been compared with those for the parent ene reaction between ethylene and propene. The exo and endo transition structures resemble rather closely that for the parent ene reaction. Reasonable substituent effects are indicated on activation energies and extents of electron transfer in the transition states. According to the calculated overlap populations, the transition structures for methyl acrylate ene reaction have less asynchronous character in the bond reorganization as compared with the parent ene reaction. The relatively small stability difference between exo and endo transition structures suggests that intrinsic exo/endo selectivity in the ene reactions is not so obvious as in th...