On inventing catalytic reactions via ruthena- or rhodacyclic intermediates for atom economy

Novel catalytic reactions via ruthena- or rhodacyclic intermediates have been developed by our research group. We initiated our study from (1) ruthenium-catalyzed [2+2] cycloaddition of alkynes with alkenes, followed by developing (2) intramolecular Pauson-Khand-type reaction of 1,6-enynes, (3) hydroquinone synthesis, (4) cyclocotrimerization reactions, and (5) codimerization of styrenes with ethylene. Another approach to construct novel functional monomers, such as cyclopentenones, pyranopyrandiones, and substituted phenols, involves cleavage of carbon-carbon bonds in cyclobutenediones, cyclopropenones, and cyclobutenones. All reactions may proceed with high atom-efficiency via ruthena- or rhodacyclic intermediates, represented by ruthenacyclopentene, (maleoyl)ruthenium, and rhodacyclopentenone intermediates. In addition, rhodium-catalyzed [2+2+2] cocyclization of alkynes with isocyanates as well as novel ruthenium-catalyzed [2+2+1] cocyclization of alkynes, isocyanates, and carbon monoxide have been disclosed.