Development of Highly Efficient Oxidation Reaction and Polymerizaztionby Utilizing the Oxidizing Ability of HyPERvalent Bismuth

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We have investigated three main topics to develop new reactions (oxidations and photo-induced cationic polymerizations) by utilizing the characteristic properties of the pentavalent bismuth. Firstly, various tetraarylbismuthonium salts were prepared and used as oxidants for alcohol oxidation. Primary and secondary alcohols were efficiently converted to the corresponding carbonyl compounds by treatment with the above Bi(V) oxidants in the presence of an organic base. It has been found that the introduction of ortho-substituents and/or electron-withdrawing para-substituents onto the aryl ligands enhances the oxidizing ability of the bismuthonium salts significantly. In particular, mesityltriarylbismuthonium salts exhibit high oxidizing ability and high chemoselectivity in the competitive reactions between primary and secondary alcohols. Secondary, we developed highly efficient Bi(V)-based cationic photoinitiators for the first time. Photoirradiation of triaryl(1-pyrenyl)bismuthonium salts in acetonitrile afforded triarylbismuthanes and pyrene, accompanied by the generation of protic acids. Triaryl(1-pyrenyl)bismuthonium hexafluoroantimonates have proven to behave as efficient photoinitiators for the cationic polymerization of oxiranes and a vinyl ether, affording the corresponding polymers in good yields within a short photoirradiation time. During the search of sensitizers, which were anticipated to photoinitiate the Bi-mediated cationic polymerization, we designed new classes of porphyrins bearing phosphorus and sulfur substituents at the meso position. Finally, we successfully prepared several meso-phosphorylporphyrins and meso-sulfinylporphyrins, and elucidated their structures, optical properties, and electrochemical properties in detail.