DEVELOPMENT AND APPLICATIONS OF BISMUTH YLIDES AND BISMUTH IMIDES IN ORGANIC SYNTHESIS

本课题旨在利用高价有机铋化合物在有机合成中的应用特点，开发基于铋叶立德(Ar_3Bi=CRR‘)和铋亚胺(Ar_3Bi=NR)的新型合成工具。(1)建立了稳定的铋叶立德和铋亚胺的合成新方法，并揭示了它们的结构和反应活性。通过歧化反应制备了亚胺基氮原子上含有酰基或磺酰基的铋亚胺化合物，并与缺电子的乙炔进行加成反应合成了稳定的铋叶立德化合物。这些化合物的X射线晶体分析表明，铋(V)-碳和铋(V)-氮键具有高度极化的单键特征。此外，还首次系统地比较了铋的亚胺化合物与轻的第15族元素对应的结构。(2)发展了以铋叶立德和铋亚胺为原料的环化新方法。例如，炔基铋盐与适当的亲核剂反应生成Ar_3Bi=C=Crr‘类型的铋叶立德，然后经过环合反应，消除三芳基二氢呋喃得到环戊烯和2，5-二氢呋喃。稳定的铋叶立德也可以通过加热或在铜催化剂的存在下环化来生成恶唑。这些转变的驱动力是三芳基铋酸根高的离开能力。(3)建立了一种选择性合成含苯乙烯基有机铋化合物的新方法。他们进行了自由基聚合，得到了含铋替代品的可溶性聚苯乙烯。(4)在铋亚胺化合物的合成研究过程中，发展了一种新的、简便的制备铋氧化物的方法，并正在对这类化合物进行进一步的研究。

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.