SYNTHESES OF HETEROCYCLES VIA ALKYNE CYCLOADDITIONS CATALYZED BY CYCLOPENTADIENYLRUTHENIUM-TYPE COMPLEXES

Transition-metal catalysis not only simplifies molecular assemblies by reducing the synthetic steps but also decreases waste production, thus accomplishing an efficient and environmentally benign synthesis of heterocycles. Ruthenium catalysis has made significant progress in the past decades, and its application to heterocycle synthesis has become one of the major research topics. In particular, organoruthenium complexes with a cyclopentadienyl-type ligand have been successfully utilized in various carbon-carbon and carbon-heteroatom bond formations. This review extensively surveys the synthetic methods of five- and six-membered heterocycles via the ruthenium-catalyzed cycloadditions of alkynes with other unsaturated compounds. The applications of the ruthenium-catalyzed heterocycle synthesis are also briefly outlined.