| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2001: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2000: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Research Abstract |
In this research project, I aimed to utilize the characteristics of hypervalent organobismuth compounds in organic synthesis and to develop new synthetic tools based on bismuth ylides (Ar_3Bi=CRR') and bismuth imides (Ar_3Bi=NR). (1) New methods for the synthesis of stabilized bismuth ylides and bismuth imides were established, and their structures and reactivities have been disclosed. Bismuth imides bearing an acyl or a sulfonyl group on the imido nitrogen atom were prepared by the metathesis reaction, and stabilized bismuth ylides were synthesized by the addition reaction of the imides with electron-deficient acetylenes. X-ray crystallographic analyses of these compounds have elucidated that the bismuth(V)-carbon and bismuth(V)-nitrodgen bonds possess a highly polarized, single bond character. Additionally, systematic comparisons of the structures of bismuth imides with those of the lighter 15th group element counterparts were made for the first time. (2) New cyclization methods by use of bismuth ylides and by bismuth imides have been developed. For instance, the reaction of alkynylbismuthonium salts with a suitable nucleophile generates bismuth ylides of the type Ar_3Bi=C=CRR', which subsequently undergo cyclization with elimination of triarylbisrnuthane to give cyclopentenes and 2,5-dihydrofurans. Stabilized bismuth ylides also undergo cyclization by heat or in the presence of a copper catalyst to afford oxazoles. The driving force of these transformations is the high leaving ability of the triarylbismuthonio group. (3) A new method for the selective synthesis of organobismuth compounds bearing a styryl group was established. They underwent radical polymerization to afford soluble polystyrenes bearing bismuth substitutes. (4) During the course of studies on the synthesis of bismuth imides, a new and convenient method for the preparation of bismuth oxides has been developed, and further studies on this class of compounds are now in progress.
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