cycloaddition

A reaction in which two or more unsaturated compounds form a cyclic adduct or in which a cyclic compound is formed by addi­tion between unsaturated parts of the same molecule. In cycloaddition, there is no net reduction in bond multiplicity. The Diels-Alder reac­tion is an example. Cycloadditions may be stepwise reactions or may be peri-cyclic reactions.