Adiraju Venkata A K, Martin Caleb D
Department of Chemistry and Biochemistry, Baylor University, One Bear Place #97348, Waco, TX, 76798, USA.
Chemistry. 2017 Aug 22;23(47):11437-11444. doi: 10.1002/chem.201702539. Epub 2017 Aug 1.
Reactions of the anti-aromatic pentaphenylborole with diazenes indicate that both the substitution and the isomer influence the reaction outcome. With respect to trans isomers, azobenzene underwent coordination and C-H addition across the diene of the borole, and 2',6'-dimethylazobenzene furnished a fused tricyclic system. Under photolytic conditions, both of the aforementioned diazenes generate the first 1,3,2-diazaborepin heterocycles, rationalized through reactivity with the cis isomers. This notion is corroborated by the reaction of pentaphenylborole with benzo[c]cinnoline, the tethered variant of azobenzene, that only exists as the cis conformer as the corresponding 1,3,2-diazaborepin was produced regardless if the reaction is conducted in the dark or light. The more aromatic pyridazine proved to be less reactive, forming a resilient adduct.
反芳香性的五苯基硼烷与重氮化合物的反应表明，取代基和异构体都会影响反应结果。对于反式异构体，偶氮苯发生配位作用，并在硼烷的二烯上进行C-H加成，而2',6'-二甲基偶氮苯则生成了稠合三环体系。在光解条件下，上述两种重氮化合物均生成了首个1,3,2-二氮杂硼戊环杂环化合物，这可通过与顺式异构体的反应活性来解释。五苯基硼烷与苯并[c]噌啉（偶氮苯的连接变体，仅以顺式构象存在）的反应证实了这一观点，无论反应是在黑暗中还是光照下进行，都会生成相应的1,3,2-二氮杂硼戊环。事实证明，芳香性更强的哒嗪反应活性较低，形成了一种稳定的加合物。
