Synthesis of Helicenes and Related Compounds Based on the Domino Cationic Cyclization of gem- Difluoroalkenes

荧光素占有（1） α-碳稳定性效应由其未共享的电子对捐赠给α-碳的真空p-轨道，（2）其离开组能力作为一种氟离子（F^-），导致其高电性。我们已经完成了一个熔化的多分子化合物的合成，从宝石-异氟烯烃开始。（1，1-difluoro-1-alkenes）通过两种属性中的两种反应都完全可用，1，1-difluoro-1-alkenes在C-3、4或5个位置被处理为FSO_3H·SbF_5通过α-氟ocarbocation进行未经验证的弗里德里克工艺循环化，由C-F键的自发水合作用形成，包括五个、六个或七个成员环，上面有动力的循环中的关键步骤是弗里德尔-工艺品类型反应，在哪里需要使用魔力酸来激活异氟烯烃的动力。为了避免这种强烈的酸性条件，我们已经成功地通过过渡约会来进行这种类型的循环化 ... More al complexes，如cationic Pd， Ru和Au complexes。特别是， [Pd（MeCN）_4]（BF_4）_2有效地推广了循环化来给予多环化合物产品。关于用Magic Acid和difluorolokenes携带两个芳基组通过成功地产生了两种α-氟酸化合物的显性循环化，其中一个被内分子芳基组捕获成两个6成员的戒指。循环化的产品已经完全被脱氢化，可以被腐蚀成腐蚀性的螺旋体。使用这一策略，我们已经完成了[4]到[6]的合成，仅在三个步骤中可以从容易获得的化合物：（一）1，1-difluoro-1-alkenes的准备， （二）多米诺弗里德尔工艺品类型循环，和（iii）脱氢化.用Et_2 AlCl诱导的Friedel-Crafts-承载2-三氟甲基-1-烯烃组的治疗类型循环化通过对碳γ组的攻击对荧光素给予外二氟甲基替代的环化合物，以及对螺旋前cursor的攻击。Less（低）

Fluorine possesses (1) α-carbocation stabilizing effect caused by donation of its unshared electron pair to the vacant p-orbital of the α-carbon, despite (2) its leaving group ability as a fluoride ion (F^-) due to its high electronegativity. We have accomplished the synthesis of fused polyaromatic compounds starting from gem-difluoroalkenes (1,1-difluoro-1-alkenes) via the reactions where both of the two properties were fully utilized.1,1-Difluoro-1-alkenes bearing a phenyl group at the C-3, 4, or 5 position were treated with FSO_3H・SbF_5 to undergo Friedel-Crafts cyclization via α-fluorocarbocations, followed by spontaneous hydrolysis of the C-F bond to afford bicyclic ketones including a five, six, or seven-membered ring.The key step in the above mentioned cyclization was the Friedel-Crafts-type reaction, where Magic acid was required to activate the difluoroalkene moiety. To avoid such strong acidic conditions, we have succeeded to conduct this type of cyclization by transition met … More al complexes, such as cationic Pd, Ru, and Au complexes. Especially, [Pd(MeCN)_4](BF_4)_2 effectively promoted the cyclization to give polycyclic products.On treatment with Magic acid, the difluoroalkenes bearing two aryl groups underwent the domino cyclization via successively generated two kinds of α-fluorocarbocations, which were trapped by the intramolecular aryl groups to construct two 6-membered rings. The cyclized products were readily dehydrogenated to afford substituted helicenes. Using this strategy we have accomplished the syntheses of [4] to [6]helicenes from easily available compounds in only three steps: (i) the preparation of 1,1-difluoro-1-alkenes, (ii) the domino Friedel-Crafts-type cyclization, and (iii) dehydrogenation.Treatment of 2-trifluoromethyl-1-alkenes bearing an aryl group with Et_2AlCl induced Friedel-Crafts-type cyclization via attack of the aryl group on the carbon γ to the fluorine to give exo-difluoromethylene-substituted cyclic compounds, the helicene precursors. Less