Ruthenium complex-catalyzed formation and cleavage of carbon-carbon sigma-bonds. On the requirement of highly qualified tuning of the reaction conditions

Characteristic aspects of ruthenium complex-catalyzed carbon-carbon bond fo rming reactions and carbon-carbon sigma -bond cleavage reactions are discus sed. It is pointed out that these ruthenium complex-catalyzed reactions req uire highly qualified tuning of reaction conditions with substrates to atta in high yields and selectivities of the products. In the [2+2] cycloadditio n of alkynes and norbomenes catalyzed by RuH2(CO)(PPh3)(3), Ru(cod)(cot)/PB u3 [cod:1,5-cyclooctadiene, cot:1,3,5-cyclooctatriene] and Cp*RuCl(cod) [Cp *: pentamethylcyclopentadienyl] giving cyclobutenes, matching of the alkyne derivative with the catalyst is essential. In the Ru,(CO),,-catalyzed intr amolecular carbonylative cyclization of 1,6-enynes giving bicyclic cyclopen tenones, remarkable solvent effects are observed. Linear codimerization of diphenylacetylene and methyl acrylate is catalyzed by Ru(cod)(cot)/pyridine ; however, for the reaction of diphenylacetylene with N,N-di-methylacrylami de, pyridine is not required. N,N-Dimethylacrylamide works as a ligand as w ell as the substrate. Ru(cod)(cot)/dimethyl fumarate catalyzes novel dimeri zation of 2,5-norbomadiene in THF to give pentacyclo[6.6.0,0(2.6).0(3.13) . 3(10.14)]tetradeca-4 1-diene (PCTD) via carbon-carbon bond cleavage. In DMS O, the major product is heptacyclo[6.6.0.0(2.6).0(3.13) .0(4.11).0(5.9).0(1 0.14)]tetradecane (HCTD) in place of PCTD, and no cleavage of the carbon-ca rbon bond occurs. The first catalytic deallylation of tert-homoallyl alcoho ls is achieved. The presence of an excess of allyl acetate is essential. Th e reaction can be applied to a ring-opening reaction of cyclic homoallyl al cohols. The reasons for the requirement of highly qualified tuning of the r eaction conditions for the ruthenium catalysts are discussed comparing with the catalytic activities of palladium complexes. Introduction Reactions via Ruthenacycles [2+2] Cycloaddition Reaction of Alkenes and Alkynes via Ruthenacyclopentene s Syntheses of Cyclopentenones via Ruthenacycles Linear Codimerization of Alkynes with Monoenes or Dienes Linear Codimerization of Internal Alkynes with Monoenes Linear Codimerizaiton of Terminal Alkynes with Dienes Organic Syntheses Involving Catalytic Cleavage of Carbon-Carbon sigma -Bond s Novel Dimerization of 2,5-Norbornadiene to PCTD Deallylation of tert-Homoallyl Alcohols General Discussion Conclusion