Chu Melody, Planas Oriol, Company Anna, Ribas Xavi, Hamilton Alex, Whiteoak Christopher J
Department of Biosciences and Chemistry , Sheffield Hallam University , Sheffield , S1 1WB , UK . Email:
Departament de Química , Grup de Química Bioinspirada, Supramolecular i Catàlisi (QBIS-CAT) , Institut de Química Computacional i Catàlisi (IQCC) , Universitat de Girona , Campus de Montilivi , 17071 Girona , Catalonia , Spain.
Chem Sci. 2019 Nov 18;11(2):534-542. doi: 10.1039/c9sc05076k. eCollection 2020 Jan 14.
Previously, an unexpected Co-catalysed remote C-H nitration of 8-aminoquinolinamide compounds was developed. This report provided a novel reactivity for Co which was assumed to proceed through the mechanistic pathway already known for analogous Cu-catalysed remote couplings of the same substrates. In order to shed light into this intriguing, and previously unobserved reactivity for Co, a thorough computational study has now been performed, which has allowed for a full understanding of the operative mechanism. This study demonstrates that the Co-catalysed remote coupling does not occur through the previously proposed Single Electron Transfer (SET) mechanism, but actually operates through a high-spin induced remote radical coupling mechanism, through a key intermediate with significant proportion of spin density at the 5- and 7-positions of the aminoquinoline ring. Additionally, new experimental data provides expansion of the synthetic utility of the original nitration procedure towards 1-naphthylpicolinamide which unexpectedly appears to operate a subtly different mechanism despite having a similar chelate environment.
此前，人们开发了一种意外的钴共催化8-氨基喹啉酰胺化合物的远程C-H硝化反应。该报告揭示了钴的一种新反应活性，该反应活性被认为是通过与相同底物的类似铜催化远程偶联反应已知的机理途径进行的。为了深入了解这种有趣的、以前未观察到的钴反应活性，现在已经进行了全面的计算研究，从而能够全面理解其作用机制。这项研究表明，钴催化的远程偶联反应不是通过先前提出的单电子转移（SET）机制发生的，而是实际上通过高自旋诱导的远程自由基偶联机制进行的，该机制通过一个关键中间体进行，该中间体在氨基喹啉环的5位和7位具有显著比例的自旋密度。此外，新的实验数据扩展了原硝化反应对1-萘基吡啶酰胺的合成应用范围，尽管具有相似的螯合环境，但该反应意外地似乎通过一种略有不同的机制进行。
