Thermal cycloadditions and their stereochemistry

Thermal cycloadditions are those cycloadditions where the reactants are in the ground electronic state. They usually have (4n + 2) ? electrons participating in the starting material, for some integer n. These reactions occur for reasons of orbital symmetry in a suprafacial-suprafacial (syn/syn stereochemistry) in most cases. Very few examples of antarafacial-antarafacial