Kinetics and Mechanism of 1,3‐Dipolar Cycloadditions

Abstract

Abstract Criteria for the mechanism of 1,3‐dipolar cycloadditions which lead to 5‐membered rings are provided by the stereoselectivity observed with cis‐trans isomeric dipolarophiles, by the effect of solvent and substituents on the rate constants, by the activation parameters, and by orientation phenomena. A concerted addition, which can also be described in terms of molecular orbitals and in which the two new σ‐bonds are formed simultaneously, although not necessarily at equal rates, offers the best explanation of the experimental facts.