Concerted vs Stepwise Mechanism in 1,3-dipolar Cycloaddition of Nitrone to Ethene, Cyclobutadiene and Benzocyclobutadiene. A Computational Study.

The problem of competition between concerted and stepwise diradical mechanisms in 1,3-dipolar cycloadditions was addressed by studying the reaction between nitrone and ethene with DFT (R(U)B3LYP/6-31G*) and post HF methods. According to calculations this reaction should take place via the concerted cycloaddition path