Hiyama coupling reaction of fluorous alkenyl-fluorosilanes: Scope and mechanistic considerations

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• 作者：Á ; gnes Csapó ; Andrea Bodor ; Jó ; zsef Rá ; bai ; ^{rabai@elte.hu}
• 关键词：Perfluoroalkylation at room temperature ; Hiyama coupling ; Fluorous styrenes ; Steam-distillation
• 刊名：Journal of Fluorine Chemistry
• 出版年：2012
• 期刊代码：52_00221139
• 类别：ch
• 出版时间：May, 2012
• 卷：137
• 期：Complete
• 页码：85-92
• 文件大小：566 K

摘要

Novel fluorous alkenyl-fluorosilanes (C_nF_2n+1CHCHSiMe₂F; n = 4, 6, 8; 5a-c) were synthetized in a three step procedure from perfluoroalkyliodides and dimethylvinylchlorosilane. They were first reacted with iodobenzene at room temperature in Hiyama coupling reaction (DMF, Pd(OAc)₂, TBAF, 72 h) to afford the appropriate 蠅-perfluoroalkyl-styrenes (C_nF_2n+1CHCHC₆H₅, n = 4, 6, 8); then the reactivity of 5a with monosubstituted iodobenzenes was studied. The coupling reaction of 5a with o-substituted iodobenzenes usually failed, while that of with the m- and p-substituted ones gave fluorous styrenes [m- or p-(C₄F₉CHCH)C₆H₄X], independently of the electronic effect of their substituent (X = Br, CF₃, CH₃, OCH₃). These volatile products can easily be isolated by steam-distilltaion and purified further by distillation.

The mechanism of the above coupling reactions was a pure Hiyama type involving fluoride-ion induced transmetallation without any Heck type contribution, since no coupling product of C₆F₁₃CHCH₂ and C₆H₅I was observed in blank control experiments using similar conditions (DMF, TBAF, Pd(OAc)₂, 72 h, 25 掳C).