Recent Advances in the Catalytic Cycloaddition of 1,n-Dipoles

Dipolar cycloaddition is one of the most valuable methods for synthesizing various carbo- and heterocycles because multiple carbon-carbon and carbon-heteroatom bonds form in a single step. Thus, practical generation of new 1,n-dipoles and control of their reactivities are significant aspects of modern organic chemistry. Although it is quite challenging to handle short-lived 1,n-dipolar species, 1,n-dipolar cycloadditions have been impressively developed in recent years. Advancement of their catalytic abilities has occurred because a catalyst enables 1,n-dipole generation and enhances the selectivities of the cycloadducts. In this Perspective, recent achievements in catalytic cycloadditions of 1,n-dipoles to synthesize medium-sized carbo- and heterocyclic compounds are addressed. Mechanistic insights and their applications toward the synthesis of natural products are also discussed.