Building Diversity in ortho-Substituted s-Aryltetrazines By Tuning N-Directed Palladium C–H Halogenation: Unsymmetrical Polyhalogenated and Biphenyl s-Aryltetrazines,ACS Catalysis

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Building Diversity in ortho-Substituted s-Aryltetrazines By Tuning N-Directed Palladium C–H Halogenation: Unsymmetrical Polyhalogenated and Biphenyl s-Aryltetrazines
ACS Catalysis ( IF 11.3 ) Pub Date : 2017-11-14 00:00:00 , DOI: 10.1021/acscatal.7b03186
Clève D. Mboyi , Christelle Testa , Sarah Reeb , Semra Genc , Hélène Cattey , Paul Fleurat-Lessard , Julien Roger , Jean-Cyrille Hierso ₁

Affiliation

We report a general route for synthesizing ortho-substituted unsymmetrical biphenyl and polyaromatic s-aryltetrazines. These compounds are inaccessible by classical Pinner hydrazine condensation or by the current s-aryltetrazine aromatic core functionalization methods described up to now. We exploited multiple versatile N-directed palladium C–H activation/halogenation of s-aryltetrazine to form C–X bonds (X = I, Br, Cl, F), which collectively produced polyhalogenated unsymmetrical building blocks. We achieved a sequence of selective C–H halogenation reactions in a specific order to produce reactive aryl halides. Polyhalogenated s-aryltetrazines can then be used for controlled cross-coupling reactions toward ortho-substituted polyaromatic s-aryltetrazines. In general, this C–H functionalization route gives access to a large number of variously halogenated building blocks practical for further synthetic implementation of tetrazines (arylation, cycloaddition, etc.). Herein, we exemplified their potential by using halogen-selective Suzuki–Miyaura reactions for divergent construction of novel biphenyl s-tetrazines. Therefore, we deliver original poly(hetero)aromatic tetrazine structures, such as new typically “Z-shaped” and “T-shaped” species. We examined by DFT calculation the origin of the remarkable regioselectivity in some C–H concurrent halogenation reactions. Computations focused at free enthalpy profiles for C–H activation of aryltetrazines to form the intermediate palladacycles by CMD process. We showed that the presence of halogen substituents on aryl groups before further halogenation increases the activation barrier to form the determining C–H activation intermediate palladacycle. XRD studies of functionalized tetrazines evidenced planarity ruptures in the mutual arrangement of aromatic cycles. Finally, this methodology allowed us to deliver a unique tetrahalogenated s-aryltetrazine holding not less than four different halogens arranged in ortho-aryl positions.

中文翻译：

通过调整N方向钯C–H卤化物来构建邻位取代的s-芳基四嗪的多样性：不对称的多卤代和联苯s-芳基四嗪

我们报告了合成邻位取代的不对称联苯和多芳族S-芳基四嗪的一般路线。这些化合物无法通过经典的Pinner肼缩合反应或目前为止描述的当前s-芳基四嗪芳族核官能化方法来获得。我们利用了多种多功能的N导向钯对s-芳基四嗪进行CH活化/卤化反应以形成CX键（X = I，Br，Cl，F），这些键共同产生了多卤代的不对称结构单元。我们按照特定的顺序完成了一系列的选择性C–H卤化反应，以生产反应性的芳基卤化物。然后可以将多卤代的s-芳基四嗪用于受控的交叉偶联反应邻取代的聚芳族s-芳基四嗪。通常，这种C–H官能化途径使人们可以使用大量各种卤化的结构单元，这些单元对于进一步合成四嗪（芳构化，环加成等）非常实用。在本文中，我们通过使用卤素选择性Suzuki-Miyaura反应示例性地说明了新型联苯s-四嗪的发散结构的潜力。因此，我们提供原始的聚（杂）芳族四嗪结构，例如新的典型的“ Z形”和“ T形”“ 物种。我们通过DFT计算检查了某些C–H同时发生的卤代反应中显着的区域选择性的起源。计算的重点是通过CMD工艺对C-H活化芳基四嗪以形成中间体Palladacycles的自由焓分布。我们表明，在进一步卤化之前，芳基上存在卤素取代基会增加活化障碍，从而形成决定性的C–H活化中间体帕拉达环。功能化四嗪的XRD研究表明，在芳族环的相互排列中，平面度破裂。最后，这种方法使我们能够提供独特的四卤代s-芳基四嗪，它含有不少于四个在邻芳基位置排列的不同卤素。

更新日期：2017-11-15

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