He Yang, Xu Dong-Hui, Zhang Yan-Jun, Zhang Chun, Guo Jian-Min, Li Laicai, Liang Xiao-Qin
College of Pharmacy, Southwest Mdeical University Luzhou 646000 China
College of Chemistry and Material Science, Sichuan Normal University Chengdu 610068 China
RSC Adv. 2021 Oct 5;11(52):32792-32798. doi: 10.1039/d1ra04636e. eCollection 2021 Oct 4.
Recently, experimentalists have developed a green and efficient method to synthesize pyrazole-fused quinones through light-induced tetrazole-quinone 1,3-dipole cycloadditions. However, the underlying microscopic mechanisms remain to be clarified. In this work, we have employed several electronic structure calculation methods (MS-CASPT2, CASSCF, DFT) to systematically explore the microscopic mechanism of related light-induced reactions and deactivation pathways. Upon excitation with ultraviolet light, one of the original reactants 2-(4-fluorophenyl)-5-phenyl-2-tetrazole (FPT) reaches its S excited state. After that, due to the ultrahigh energy and the small energy barrier, the FPT molecule breaks the N2-N3 and N4-C5 bonds sequentially, removing the nitrogen atom finally in the S state. Combined with the cleavage of the second N4-C5 bond, the system reaches its conical intersection region and deactivates ultrafast to the ground state, generating the active intermediate ((4-fluorophenyl)diazen-1-ium-1-ylidene) (phenyl)methanide (FPNI). Subsequently, the active intermediate FPIN can react with naphthoquinone in the ground state by overcoming an energy barrier of about 5.7 kcal mol, after which the 1-(4-fluorophenyl)-3-phenyl-1-benzo[f]indazole-4,9(3aH, 9aH)-dione (FP2HQ) is formed. The FP2HQ can be oxidized to obtain the 1-(4-fluorophenyl)-3-phenyl-1-benzo[]indazole-4,9-dione (PFQ). Due to the high energy and small barrier, the entire reaction process can easily take place, which ultimately leads to the efficient reaction. Our present work not only explains the experimental mechanism in detail but can also be helpful for the future design of related photoinduced reactions with the aid of theoretical calculations.
最近，实验人员开发了一种绿色高效的方法，通过光诱导的四唑-醌1,3-偶极环加成反应合成吡唑并醌。然而，其潜在的微观机制仍有待阐明。在这项工作中，我们采用了几种电子结构计算方法（MS-CASPT2、CASSCF、DFT）来系统地探索相关光诱导反应的微观机制和失活途径。在用紫外光激发后，原始反应物之一2-(4-氟苯基)-5-苯基-2-四唑（FPT）达到其S激发态。此后，由于超高的能量和较小的能垒，FPT分子依次断裂N2-N3和N4-C5键，最终在S态去除氮原子。结合第二个N4-C5键的断裂，系统到达其锥形交叉区域并超快失活至基态，生成活性中间体((4-氟苯基)重氮-1-亚基)(苯基)甲烷化物（FPNI）。随后，活性中间体FPIN可以通过克服约5.7 kcal mol的能垒与基态的萘醌反应，之后形成1-(4-氟苯基)-3-苯基-1-苯并[f]吲唑-4,9(3aH,9aH)-二酮（FP2HQ）。FP2HQ可以被氧化以获得1-(4-氟苯基)-3-苯基-1-苯并[]吲唑-4,9-二酮（PFQ）。由于能量高且能垒小，整个反应过程很容易发生，最终导致反应高效进行。我们目前的工作不仅详细解释了实验机制，而且借助理论计算对未来相关光诱导反应的设计也有帮助。
