Selective Generation of Carbocations and Construction of Fused Ring Systems by Using α-Cation-Stabilizing Effect of Fluorine

利用氟的α-阳离子稳定作用选择性生成碳正离子并构建稠环体系

基本信息

批准号：
11650899
负责人：
ICHIKAWA Junji
金额：
$ 2.24万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

Fluorine possesses (i) α-cation-stabilizing effect and (ii) leaving-group ability as fluoride ion (F^-). Using these properties, we have recently developed fluorine-directed Nazarov cyclizations via α-fluorocarbocations generated from 2,2-difluorovinyl vinyl ketones. Our interest on fluorine-containing carbocations prompted us to investigate their generation from simple 1,1-difluoroolefins without a carbonyl group, which would allow ring constructions by intramolecular trapping of the cations with unsaturated groups. Furthermore, to expand the scope of α-fluorocarbocation chemistry, we also explored the generation of fluoroallyl cations from conjugated 1,1-difluorodienes by regioselective protonation of the non-fluorinated double bond. Thus, we have accomplished intramolecular Friedel-Crafts cyclizations of 1,1-difluoro-1-alkenes and 1,1-difluoro-1,3-alkadienes bearing one or two aryl groups. These reactions efficiently provide a variety of fused polycyclic compounds.Treatment of 1,1-difluoro-1-alkenes or 1,1-difluoro-1,3-alkadienes bearing an aryl group with FSO_3H SbF_5 or p-toluenesulfonic acid, respectively, promotes intramolecular Friedel-Crafts reactions in (CF_3)_2CHOH (HFIP). The cyclizations proceed via terminal α-fluorocarbocations generated by regioselective protonation of the double bond. Bicyclic ketones are eventually obtained after spontaneous hydrolysis of the C-F bonds.In the case of difluoroolefins bearing two aryl groups, tandem cyclizations successfully occur to afford fused polycyclic compounds, whose dehydrogenation with palladium on activated carbon leads to [4]helicenes in high yields.

氟具有（i）α-结 - 稳定作用，（ii）将组作为氟离子（f^ - ）。使用这些特性，我们最近通过由2,2-二氟烷基乙烯基酮产生的α-氟化碳环酮开发了氟定向的纳扎罗夫周期。我们对含氟的碳酸化的兴趣促使我们研究了它们从没有羰基的简单1,1-二氟烯烯的产生，这将允许通过分子内捕获阳离子以不饱和组的分子捕获来构建环。此外，为了扩大α-氟化学化学的范围，我们还通过调节非荧光双键的调节质子化来探索从共轭1,1-二氟二烯中产生的氟乙烯阳离子。这是我们完成了1,1-二氟-1-烯烃和1,1-二氟-1,3-烷基的1,1-二氟此类的分子内Friedel-Crafts环化，具有一两个芳基群。这些反应有效地提供了各种融合的多环化合物。对带有FSO_3H SBF_5或p-toluenesulfonic酸的芳基的1,1-二氟-1-烯烃或1,1-二氟曲霉1,3-烷基的处理，分别促进了内核酸的FRIEDEL-CRESTION RECTION（COCT）RECTION（COCT）。（HFIP）。环化通过双键的调节性选择性质子化产生的末端α-氟化合物进行。自行车酮有时在赞助C-F键水解后获得。在携带两个芳基的二氟甲苯蛋白的情况下，成功进行了串联循环，以提供融合的多环化合物，其在高收益率中脱氢在高收益率上的活性碳引起了钯的脱氢。