Diels-Alder Reactions of Aza- and Phospha-1,3-butadienes with Ethylene. An ab initio Study.

The Diel-Alder (DA) reactions of ethylene with 1,3-butadiene, (Z)-1-aza-butadiene, (E)-1-aza-1,3-butadiene, 2-aza-1,3-butadiene, (Z)-1-phospha-1,3-butadiene, (E)-1-phospha-1,3-butadiene, and 2-phospha-1,3-butadiene were examined using ab initio calculations. All structures, including the transition structures, were completely optimized at HF/6-31G * and MP2/6-31G * which single-point energies evaluated at MP4SDQ