Novel Organic Syntheses by Reconstruction of Carbon Skeletons via Catalytic Carbon-Carbon Bond Cleavage

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Bicyclo[2.2.1]hepta-2, 5-diene(2, 5-norbornadiene)dimerizes in the presence of a catalytic amount of Ru(1-2 : 5-6-η-cyclooctadiene)(1-6-η-cyclooctatriene)(Ru(η^4-cod)(η^6-cot))and an electron-deficient olefin such as N, N-dimethylacrylamide, dimethyl fumarate or dimethyl maleate in toluene or THF to give a new compound, pentacyclo[6.6.0^<2,6>.0^<3,13>.0^<10,14>]tetradeca-4, 11-diene(PCTD), in excellent yield. The structure of PCTD was directly determined by X-ray analysis of its derivative, [AgOTf(PCTD)]_n. PCTD was found to be derived via endo-endo dimerization of 2, 5-norbornadiene. Formation of PCTD from two molecules of 2, 5-norbomadiene involves the cleavage of two carbon-carbon bonds. Ru(η^4-cod)(η^6-cot)reacts with dimethyl fumarate to give a novel complex, Ru(1-6-η-cyclooctatriene)(η^2-dimethyl fumarate)_2, in high yield. The structure of the complex was also determined by X-ray analysis. At 40 ℃ in toluene, Ru(η^6-cot)(η^2-dmfm)_2 itself catalyzes the dimerization of 2, 5-norb … More ornadiene to give PCTD in excellent yield in the absence of olefinic additives, which enabled the large scale synthesis of PCTD(ca. 20 g). In consideration of all findings, the possible mechanisms of the formation of PCTD are discussed in detail.To prepare various novel caged compounds, derived from PCTD, which can be expected as highly functional monomers, the following oxidation reactions of PCTD were examined. Oxidation of PCTD with hydrogen peroxide catalyzed by methyltrioxorhenium selectively gave the exo, exo-diepoxide in high yield. Osmium tetraoxide catalyzed selective syn-exo-tetrahydroxylation or syn-exo-dihydroxylation of PCTD with N-methylmorphorine N-oxide. Ruthenium trichloride-catalyzed oxidative cleavage of the olefinic groups in PCTD with sodium periodate gave a derivative of tricyclodecanecarboxylic acid with two lactone rings.Finally, we found that Ru(η^6-cot)(η^2-dmfm)_2, which is easily prepared from Ru(η^4-cod)(η^6-cot), smoothly reacts with monodentate or bidentate amine and phosphine ligands to give a variety of the corresponding novel ruthenium(0)amine and phosphine complexes, which can be expected to have high catalytic activities toward carbon-carbon bond forming reactions as well as carbon-carbon bond cleavage reactions. Less