A Theoretical Study of the Endo/Exo Selectivity of the Diels-Alder Reaction between Cyclopropene and Butadiene

摘要

Molecular orbital calculations using Hartree-Fock (HF), complete active space self consistent field (CASSCF), quadratic configuration interaction with single and double excitations, and triple excitations included via perturbation (QCISD(T)) and semiempirical (AM1) methods suggest that the experimentally observed endo selectivity for the Diels-Alder reaction between cyclopropene, I, and isotopically substituted butadiene, Ⅱ, be mostly due to an attractive interaction between a C-H of I and the π-bond between the central carbons of Ⅱ, which is possible in the endo (but not exo) transition state.