| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2003: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2002: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
A systematic series of triarylbismuthane oxides were prepared by treatment of the corresponding triarylbismuth dichlorides with excess water in the presence of two equivalents of potassium tert-butoxide. We disclosed the structures, thermal stability, and reactivity of this class of compounds. The bismuthane oxides exist as a dimeric, hydrated, or oligomeric form, depending on the structure of the aryl ligands attached to the bismuth center. It was found that the bismuthane oxides are thermally unstable and readily decompose to give triarylbismuthanes as the major products. Among the insoluble bismuth-derived byproducts, we successfully characterized the structure of a diarylbismuthinic anhydride by X-ray crystallography. It also was found that the oxidizing ability of the bismuthane oxides is much higher than those of lighter pnictogen counterparts, and is significantly enhanced by introducing ortho-substituents onto the aryl ligands. Based on this finding, we developed a new efficient method for alcohol oxidation using a triarylbismuth dichloride/DBU system, where primary and secondary alcohols were readily oxidized to the corresponding carbonyl compounds in good yields under mild conditions. In this system, the remarkably high substituent effects on the oxidizing ability were observed. Thus, introduction of an electron-withdrawing substituent at the para position and a methyl group at the ortho position enhances the rate of oxidation.
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