Exploitation of Nitroxyl Radidal-type Organocatalysts for Alcohol Oxidation and their Use in Fine Synthetic Chemistry

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This research project aimed exploitation of synthetic potential of azaadamantane N-oxyl (AZADO)-type nitroxyl radicals as oxidation catalyst for alcohol oxidation and their use in fine synthetic chemistry. We have established the following matters in this research period.(1) The structure-activity correlation of AZADO-type nitroxyl radicals: We synthesized a panel of AZADO-type catalysts and examined their function as oxidation catalyst to clarify the molecular basis of the extremely aggressive nature of AZADO compare to TEMPO. Our experiments have led the conclusion that alleviation of the steric factor near the catalytically active site critically determine the catalytic activity.(2) We have developed several synthetic route to enantiomerically modified AZADOs and have examined their use as enantioselective catalyst for oxidation of secondary alcohols. The results allowed us to develop a tentative mechanistic hypothetic model, which is useful for further development.(3) We have developed a ractical and highly efficient methods for oxidative rearrangement of tertiary allylic alcohols to β-substituted α,β-unsaturated ketones employing oxoxammonium salts. The methods developed are applicable to acyclic substrates as well as medium membered ring substrates and macrocyclic substrates. We have elucidated that counter anion of the oxoxmmonium salt plays crucial roles on this oxidative rearrangement.(4) We have discovered a novel AZADO derivative that made us possible to conduct metal-free, halogen-free aerobic oxidation of aloohols to carbonyl compounds under an ambient temperature.