Transient Imine as a Directing Group for the Metal-Free o-C?H Borylation of Benzaldehydes
Transient Imine as a Directing Group for the Metal-Free o-C?H Borylation of Benzaldehydes
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瞬态亚胺作为苯甲醛无金属邻-C?H硼化的导向基团
DOI：
10.1021/jacs.0c13013
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发表时间：
2021
影响因子：
15
通讯作者：
Chatani Naoto
中科院分区：
文献类型：
--
作者：
Rej Supriya;Chatani Naoto
有机硼试剂是重要的合成中间体，在有机合成中有着广泛的应用。目前使用的选择性硼基化策略主要依赖于过渡金属催化剂的使用。因此，确定温和得多的条件下过渡金属无硼基化将是非常可取的。我们在此提出了一个统一的策略，选择性C-H硼基化的缺电子苯甲醛衍生物使用一个简单的无金属的方法，利用亚胺瞬态导向基团。该策略涵盖了广泛的反应范围，并且（i）即使是高度空间位阻的C-H键也可以顺利地硼化，（ii）尽管存在其他潜在的导向基团，反应选择性地发生在苯甲醛部分的o-C-H键上，以及（iii）天然产物附加到苯甲醛衍生物上也可以得到适当的硼化产物。此外，该方案的有效性得到了以下事实的证实：即使在存在一系列外部杂质的情况下，反应也能进行。
Organoboron reagents are important synthetic intermediates and have wide applications in synthetic organic chemistry. The selective borylation strategies that are currently in use largely rely on the use of transition-metal catalysts. Hence, identifying much milder conditions for transition-metal-free borylation would be highly desirable. We herein present a unified strategy for the selective C–H borylation of electron-deficient benzaldehyde derivatives using a simple metal-free approach, utilizing an imine transient directing group. The strategy covers a wide spectrum of reactions and (i) even highly sterically hindered C–H bonds can be borylated smoothly, (ii) despite the presence of other potential directing groups, the reaction selectively occurs at theo-C–H bond of the benzaldehyde moiety, and (iii) natural products appended to benzaldehyde derivatives can also give the appropriate borylated products. Moreover, the efficacy of the protocol was confirmed by the fact that the reaction proceeds even in the presence of a series of external impurities.