Exploitation of New Catalytic Methods for the Construction of Carbon Frameworks and the Control of Reaction Fields

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(1) There have been no systematic study on organoruthenium chemistry with high oxidation states until this project was started. Several new pi-allyl ruthenium(IV) complexes bearing cyclopentadinyl(Cp) or pentamethylcyclopentadienyl(Cp^*) ligands were successfully prepared in this project for the first time. The X-ray structure determination of the representative Cp^*Ru(pi-allyl)Br_2 was undertaken. Several important aspects on the chemical reactivity of the carbon-ruthenium(IV) bonds in these new organoruthenium(IV) compounds were investigated in detail. Judicious combinations of the elemental organometallic reactions provide new highly selective catalyses based on Ru(II)-Ru(IV) redox channel. Linear oligomerization of butadiene or 1,3-pentadiene proceeds with "CpRu^+" or "Cp^*Ru^+" type catalysts. Furthermore, a cyclic dimerization of butadiene or isoprene was found to take place under mild condition to give the corresponding eight-membered carbocyclic frameworks with extremely high r … More egio- and stereo-selectivity by means of "Cp^*Ru^+" catalyst. A reasonable mechanism was elucidated based on a number of stoichiometric model reactions between Cp^*RuX(diene)/AgOTf and the conjugated dienes.(2) Single electron transfer from Cu(I) or Ru(II) complexes was found to be extremely effective redox channel to the intramolecular radical addition to form C-C bonds. This original concept makes stoichiometric radical cyclizations to homogeneous catalytic processes. New catalytic radical cyclization was exploited for the construction of trichlorinated gamma-lactam or lactone skeletons starting from the appropriate acyclic precursors such as N-allyltrichloroacetamide or allyltrichloroacetate derivatives. These new methodologies were extended to some sequential multi-step radical cyclization, and to the asymmetric induction at the geminal carbon atoms on the lactam or lactone skeletons.(3) Completely novel chiral auxiliary, bis(oxazolinyl)pyridine, was designed and successfully synthesized. Its rhodium(III) complex provides a terdentate meridional C_2-chiral reaction field for enantioselective catalysis. Less