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

在这个研究项目中，我的目标是利用高价有机铋化合物在有机合成中的特点，开发基于铋化物（Ar_3Bi=CRR'）和铋亚胺（Ar_3Bi=NR）的新的合成工具。(1)建立了稳定铋化物和铋亚胺的合成新方法，并公开了它们的结构和反应活性。通过还原反应制备了在亚胺氮原子上带有酰基或磺基的亚胺铋，并通过亚胺与缺电子乙炔的加成反应合成了稳定的亚胺铋。这些化合物的x射线晶体学分析表明，铋(V)-碳键和铋(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亚胺与较轻的15族元素的结构。(2)开发了铋酰化和铋亚胺化的新环化方法。例如，炔基铋鎓盐与合适的亲核试剂反应生成类型为Ar_3Bi=C=CRR'的铋酰化物，随后经过环化，消除三芳基铋烷，得到环戊烯和2,5-二氢呋喃。稳定的铋化物也经过热环化或在铜催化剂的存在下生成恶唑。这些转变的驱动力是三芳基铋的高离开能力。(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。它们经过自由基聚合得到含铋替代品的可溶性聚苯乙烯。(4)在合成亚胺铋的研究过程中，发现了一种制备氧化铋的简便新方法，对该类化合物的进一步研究正在进行中。

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.