1,3-Dipolar cycloaddition reactions of azomethine ylides with aromatic dipolarophiles

The 1,3-dipolar cycloadditions of azomethine ylides to aromatic dipolarophiles are reviewed and discussed. The reaction proceeds with stabilized and non-stabilized azomethine ylides, although most studies have been with non-stabilized systems. While simple benzene derivatives do not readily undergo such 1,3-dipolar cycloaddition reactions, the dipolarophilic character of benzene emerges when the benzenoid nucleus is embedded within a polycyclic aromatic hydrocarbon, tethered with the azomethine ylide (an intramolecular process) or substituted with highly electron withdrawing nitro groups. Heteroaromatic systems display similar tendencies towards such cycloaddition processes. The review closes with a consideration of the mechanism of the reactions.