Carboboration‐Driven Generation of a Silylium Ion for Vinylic C-F Bond Functionalization by B(C6F5)3 Catalysis
Carboboration‐Driven Generation of a Silylium Ion for Vinylic C-F Bond Functionalization by B(C6F5)3 Catalysis
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B(C6F5)3 催化碳硼化驱动生成乙烯基 C-F 键官能化硅离子
DOI：
10.1002/chem.202103852
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Yasuda Makoto
中科院分区：
文献类型：
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作者：
Yata Tetsuji;Nishimoto Yoshihiro;Yasuda Makoto
已知强主族刘易斯酸如甲硅烷基离子可有效促进异裂解C（sp3）−F键裂解。然而，进行乙烯基C-F键的C（sp2）-F键转化仍然是一个未满足的挑战。在此，我们描述了一种新的和简单的策略，α-氟苯乙烯与硅烷基烯酮缩醛的乙烯基C−F键转化的B（C6 F5）3在温和的条件下催化的发展。我们的理论计算表明，通过碳硼化反应从甲硅烷基烯酮缩醛生成的稳定的甲硅烷基离子裂解α-氟苯乙烯的C−F键。对α-氯代苯乙烯或溴代苯乙烯的比较研究表明，我们的反应仅适用于α-氟代苯乙烯，因为强的硅-氟亲合力促进了硅离子与氟原子的分子内相互作用，以裂解C-F键。一系列的α-氟苯乙烯以及一系列的甲硅烷基乙烯酮缩醛都经历了这种C-F键的转变。
Strong main‐group Lewis acids such as silylium ions are known to effectively promote heterolytic C(sp3)−F bond cleavage. However, carrying out the C(sp2)−F bond transformation of vinylic C−F bonds has remained an unmet challenge. Herein, we describe our development of a new and simple strategy for vinylic C−F bond transformation ofα‐fluorostyrenes with silyl ketene acetals catalyzed by B(C6F5)3under mild conditions. Our theoretical calculations revealed that a stabilized silylium ion, which is generated from silyl ketene acetals by carboboration, cleaves the C−F bond ofα‐fluorostyrenes. A comparative study ofα‐chloro or bromostyrenes demonstrated that our reaction can be applied only toα‐fluorostyrenes because the strong silicon‐fluorine affinity facilitates an intramolecular interaction of silylium ions with fluorine atom to cleave the C−F bond. A broad range ofα‐fluorostyrenes as well as a range of silyl ketene acetals underwent this C−F bond transformation.