Insertion reactions of allenes with transition metal complexes

Recently, allenes have been widely used as starting materials to synthesize various organic compounds and polymeric materials, especially through reactions catalyzed by transition metal catalysts. In many of the catalytic reactions, insertion of allenes is one of the most important elementary steps. In this review, stoichiometric insertion reactions of transition metal complexes with allenes affording well-defined inserted products are summarized, which may help chemists to understand the mechanisms of catalytic reactions of allenes and to design new catalytic reactions of allenes.