Catalytic electrophilic reactions of chrysanthemic acid derivatives with unsaturated organosilanes. An application to synthesis of modified types of C15 and C20 isoprenoids with non-head-to-tail linkages
Catalytic electrophilic reactions of chrysanthemic acid derivatives with unsaturated organosilanes. An application to synthesis of modified types of C15 and C20 isoprenoids with non-head-to-tail linkages
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菊酸衍生物与不饱和有机硅烷的催化亲电反应。
DOI：
10.1021/jo00374a012
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
S. Eguchi*
中科院分区：
文献类型：
--
作者：
M. Ohno*;S. Matsuoka;S. Eguchi*
菊花基硅醚(2b)在TiCl4催化下与烯丙基硅烷和烯醇式硅烷反应，选择性地得到C^CG开环和取代产物(yomogi型产物)。菊醛(3)和相应的甲基酮4与这些试剂发生了类似的亲电反应。这些结果被催化剂辅助下形成的中间体高戊二烯基阳离子对不饱和有机硅烷的亲电攻击所解释。在反应活性方面，正构异构体占优势，与2，4-二硝基苯甲酸菊酯(2c)的溶解行为一致。不同于TiCl4与3反应生成1，2加成产物的不同产物模式支持Mukaiyama反应的机理是与TiCl4反应的初始极化，而不是TiCl4的生成。该方法使用C5有机硅烷，通过组合C5+C10和C5+C10+C5分别构建了修饰的C16和Cgo类异戊二烯骨架。因此，即使是所有异戊二烯从中到尾融合的C20化合物也是可以得到的。特别令人感兴趣的是醛3与甲基异丙基酮的烯醇酸锂缩合反应所得的烯酮42的反应；该反应发生在羰基中心的-位置。反应中心的异常伸长可能源于环丙烷环应变的缓解。
Chrysanthemyl silyl ether (2b) reacted with allylic and enolicsilanes in the presence of TiCl4 as a catalyst to give selectively C^ Cg ring-opened and «-substituted products (yomogi type product). Chrysanthemaldehyde (3) and the corresponding methyl ketone 4 underwent similar electrophilic reactions with these reagents. These results are rationalized by the electrophilic attack of the intermediate homopentadienyl cation formed by the aid of the catalyst on an unsaturated organosilane. As for the reactivity, thetrans isomer prevailed over the cis isomer, coinciding with the solvolytic behavior of chrysanthemyl 2, 4-dinitrobenzoate (2c). The different product pattern from that in the reaction of Ti (IV) enolate with 3 giving a straightforward 1, 2 addition product supported that the mechanism for the Mukaiyama reaction involves the initial polarization of a carbonyl group with TiCl4 rather than Ti (IV) enolate formation. This method employing C5 organosilanes constructed modified C16 andCgo isoprenoid skeletons with non-head-to-taillinkages by combinations C5+ C10 and C5+ C10+ C5, respectively. Thereby, even the C20 compound with all the isoprenoid fusions in middle-to-tail was obtainable. Of particular interest was the reaction of the enone 42 derived from the condensation reaction of the aldehyde 3 and lithium enolate of methyl isopropylketone; the reaction occurred at the-position to the carbonyl center. The unusual elongation of the reactive site may originate from the cyclopropane ring strain relief.