Shen Guang-Bin, Xie Li, Yu Hao-Yun, Liu Jie, Fu Yan-Hua, Yan Maocai
School of Medical Engineering, Jining Medical University Jining Shandong 272000 P. R. China.
College of Chemistry and Environmental Engineering, Anyang Institute of Technology Anyang Henan 455000 P. R. China.
RSC Adv. 2020 Aug 25;10(52):31425-31434. doi: 10.1039/d0ra06745h. eCollection 2020 Aug 21.
Recently, a variety of 4-substituted Hantzsch esters (XRH) with different structures have been widely researched as alkylation reagents in chemical reactions, and the key step of the chemical process is the elementary step of XRH˙ releasing R˙. The purpose of this work is to investigate the essential factors which determine whether or not an XRH is a great alkylation reagent using density functional theory (DFT). This study shows that the ability of an XRH acting as an alkylation reagent can be reasonably estimated by its Δ (XRH˙) value, which can be conveniently obtained through DFT computations. Moreover, the data also show that Δ (XRH˙) has no simple correlation with the structural features of XRH, including the electronegativity of the R substituent group and the magnitude of steric resistance; therefore, it is difficult to judge whether an XRH can provide R˙ solely by experience. Thus, these results are helpful for chemists to design 4-substituted Hantzsch esters (XRH) with novel structures and to guide the application of XRH as a free radical precursor in organic synthesis.
最近，各种具有不同结构的4-取代汉茨希酯（XRH）作为化学反应中的烷基化试剂受到了广泛研究，并且该化学过程的关键步骤是XRH˙释放R˙的基元步骤。这项工作的目的是使用密度泛函理论（DFT）研究决定XRH是否为优良烷基化试剂的关键因素。该研究表明，XRH作为烷基化试剂的能力可以通过其Δ （XRH˙）值合理估计，该值可通过DFT计算方便地获得。此外，数据还表明，Δ （XRH˙）与XRH的结构特征没有简单的相关性，包括R取代基的电负性和空间阻力大小；因此，仅靠经验很难判断XRH是否能提供R˙。因此，这些结果有助于化学家设计具有新颖结构的4-取代汉茨希酯（XRH），并指导XRH作为自由基前体在有机合成中的应用。
