Organoboranes are among the most versatile and widely used reagents in synthetic chemistry. A significant further expansion of their application spectrum would be achievable if boron-containing reactive intermediates capable of inserting into C–H bonds or performing nucleophilic substitution reactions were readily available. However, current progress in the field is still hampered by a lack of universal design concepts and mechanistic understanding. Herein we report that the doubly arylene-bridged diborane(6) 1H₂ and its BB-bonded formal deprotonation product Li₂[1] can activate the particularly inert C(sp³)–H bonds of added H₃CLi and H₃CCl, respectively. The first case involves the attack of [H₃C]⁻ on a Lewis-acidic boron center, whereas the second case follows a polarity-inverted pathway with nucleophilic attack of the BB double bond on H₃CCl. Mechanistic details were elucidated by means of deuterium-labeled reagents, a radical clock, α,ω-dihaloalkane substrates, the experimental identification of key intermediates, and quantum-chemical calculations. It turned out that both systems, H₃CLi/1H₂ and H₃CCl/Li₂[1], ultimately funnel into the same reaction pathway, which likely proceeds past a borylene-type intermediate and requires the cooperative interaction of both boron atoms.

中文翻译：

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具有氧化还原活性的乙硼烷平台进行 C(sp3)–H 活化和亲核取代反应†

有机硼烷是合成化学中用途最广泛、用途最广泛的试剂之一。如果能够插入 C-H 键或进行亲核取代反应的含硼反应性中间体很容易获得，则可以实现其应用范围的显着进一步扩展。然而，目前该领域的进展仍然受到缺乏通用设计理念和机械理解的阻碍。在此我们报道了双亚芳基桥接的乙硼烷(6) 1 H ₂及其B B 键合的形式去质子化产物Li ₂ [ 1 ] 可以激活添加的H ₃ CLi 和H的特别惰性的C(sp ³ )-H 键。₃CCl，分别。第一种情况涉及[H ₃ C] ^-对路易斯酸性硼中心的攻击，而第二种情况遵循极性反转途径，B B 双键对H ₃ CCl 进行亲核攻击。通过氘标记试剂、自由基钟、α,ω-二卤代烷底物、关键中间体的实验鉴定和量子化学计算阐明了机理细节。结果表明，这两个系统，H ₃ CLi/ 1 H ₂和 H ₃ CCl/Li ₂ [ 1]，最终流入相同的反应途径，这可能会经过硼烯型中间体，需要两个硼原子的协同作用。