Generation and reaction of tungsten-containing carbonyl ylides: [3+2]-cycloaddition reaction with electron-rich alkenes
Generation and reaction of tungsten-containing carbonyl ylides: [3+2]-cycloaddition reaction with electron-rich alkenes
复制标题
DOI：
10.1021/ja044194k
复制
发表时间：
2005-03-02
影响因子：
15
通讯作者：
Iwasawa, N
中科院分区：
文献类型：
--
作者：
Kusama, H;Funami, H;Iwasawa, N
以W(CO)(5)（thf）为催化量的邻炔基苯基羰基衍生物1与烯烃通过[3 + 2]-环加成反应生成多环化合物5，然后在分子内插入C-H，生成不稳定的羰基络合物中间体8。在三乙基硅烷存在的情况下，这些含钨的碳中间体8被三乙基硅烷顺利地捕获在分子间，生成含硅环加合物17，并使W(CO)5再生。通过这种方法，澄清了可用于该反应的烯烃的范围。通过直接观察邻乙基苯基酮1c与W(CO)(5)（thf-d(8)）的混合物，证实了含钨羰基化合物7c的存在。通过二维核磁共振对中间体进行了仔细的分析，并观察了使用c -13标记的底物与钨-183的直接偶联，证实了ylide 7c的结构。使用(E)-或(2)-乙烯醚进行检查表明，[3 + 2]-环加成反应以一致的方式进行，反应的表面选择性因三乙基硅烷的存在或不存在而有很大差异。这些结果阐明了[3 + 2]-环加成反应的可逆性质。
Novel tungsten-containing carbonyl ylides 7, generated by the reaction of the o-alkynylphenyl carbonyl derivatives 1 with a catalytic amount of W(CO)(5)(thf), reacted with alkenes to give polycyclic compounds 5 through [3 + 2]-cycloaddition reaction followed by intramolecular C-H insertion of the produced nonstabilized carbene complex intermediates 8. In the presence of triethylsilane, these tungsten-containing carbene intermediates 8 were smoothly trapped intermolecularly by triethylsilane to give silicon-containing cycloadducts 17 with regeneration of the W(CO)5 species. By this procedure, the scope of alkenes employable for this reaction was clarified. The presence of the tungsten-containing carbonyl ylide 7c was confirmed by direct observation of the mixture of o-ethynylphenyl ketone 1c and W(CO)(5)(thf-d(8)). Careful analysis of the intermediate by 2D NMR, along with the observation of the direct coupling with tungsten-183 employing the C-13-labeled substrate, confirmed the structure of the ylide 7c. Examination using (E)- or (2)- vinyl ether revealed that the [3 + 2]-cycloaddition reaction proceeded in a concerted manner and that the facial selectivity of the reaction differed considerably depending on the presence or absence of triethylsilane. These results clarified the reversible nature of this [3 + 2]-cycloaddition reaction.