[2+2+2] Cycloaddition Reactions Catalyzed by Transition Metal Complexes

Recent progress in the synthesis of benzene and 1,3‐cyclohexadiene derivatives, and heterocyclic compounds such as pyridines, pyridones, pyrans, pyrimidine diones, etc, has been reviewed. The general mechanistic aspects of the [2+2+2] cycloaddition reaction are discussed. The asymmetric variants of these reactions are also discussed along with the proposed models of asymmetric induction.