In the present work, the bond breaking/forming events along the intramolecular Diels–Alder (IMDA) reaction of (2E,4Z,6Z)-2(allyloxy)cycloocta-2,4,6-trien-1-one have been revealed within bonding evolution theory (BET) at the density functional theory level, using the M05-2X functional with the cc-pVTZ basis set. Prior to achieving this task, the energy profiles and stationary points at the potential energy surface (PES) have been characterized. The analysis of the results finds that this rearrangement can proceed along three alternative reaction pathways (a–c). Paths a and b involve two steps, while path c is a one-step process. The first step in path b is kinetically favored, and leads to the formation of an intermediate step, Int-b. Further evolution from Int-b leads mainly to 3-b1. However, 2 is the thermodynamically preferred product and is obtained at high temperatures, in agreement with the experimental observations. Regarding the BET analysis along path b, the breaking/forming process is described by four structural stability domains (SSDs) during the first step, which can be summarized as follows: (1) the breaking of the C–O bond with the transfer of its population to the lone pair (V(O)), (2) the reorganization of the electron density with the creation of two V(C) basins, and (3) the formation of a new C–C single bond via the merger of the two previous V(C) basins. Finally, the conversion of Int-b (via TS2-b1) occurs via the reorganization of the electron density during the first stage (the creation of different pseudoradical centers on the carbon atoms as a result of the depopulation of the C–C double bond involved in the formation of new single bonds), while the last stage corresponds to the non-concerted formation of the two new C–C bonds via the disappearance of the population of the four pseudoradical centers formed in the previous stage. On the other hand, along path a, the first step displays three SSDs, associated with the depopulation of the V(C2,C3) and V(C6,C7) basins, the appearance of the new monosynaptic basins V(C2) and V(C7), and finally the merging of these new monosynaptic basins through the creation of the C2–C7 single bond. The second step is described by a series of five SSDs, that account for the reorganization of the electron density within Int-a via the creation of four pseudoradical centers on the C12, C13, C3 and C6 carbon atoms. The last two SSDs deal with the formation of two C-C bonds via the merging of the monosynaptic basins formed in the previous domains.

中文翻译：

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利用成键演化理论探索(2E,4Z,6Z)-2(烯丙氧基)环辛基-2,4,6-三烯-1-酮分子内狄尔斯-阿尔德反应机理

在目前的工作中，揭示了 (2E,4Z,6Z)-2(烯丙氧基)cycloocta-2,4,6-trien-1-one 分子内狄尔斯-阿尔德 (IMDA) 反应的断键/形成事件在密度泛函理论水平的成键演化理论 (BET) 中，使用具有 cc-pVTZ 基组的 M05-2X 泛函。在完成此任务之前，已对势能面 (PES) 处的能量分布和驻点进行了表征。结果分析发现，这种重排可以沿着三种替代反应途径（a-c）进行。路径a和b涉及两步，而路径c是一步过程。路径 b 中的第一步在动力学上是有利的，并导致中间步骤 Int-b 的形成。Int-b 的进一步演化主要导致 3-b1。然而，2 是热力学上优选的产物，并且是在高温下获得的，与实验观察结果一致。关于沿路径 b 的 BET 分析，第一步中的四个结构稳定域（SSD）描述了断裂/形成过程，可概括如下：（1）C-O 键的断裂，伴随着 C-O 键的转移其数量变为孤对电子 (V(O))，(2) 通过创建两个 V(C) 盆地来重组电子密度，以及 (3) 通过合并形成新的 C-C 单键前两个 V(C) 盆地。最后，Int-b（通过 TS2-b1）的转换是通过第一阶段中电子密度的重组而发生的（由于 C-C 双键的减少，在碳原子上创建了不同的伪自由基中心）参与新单键的形成），而最后一个阶段对应于通过前一阶段形成的四个伪自由基中心群体的消失而非协同形成两个新的C-C键。另一方面，沿着路径a，第一步显示三个SSD，与V(C2,C3)和V(C6,C7)盆地的减少、新的单突触盆地V(C2)和V的出现相关(C7)，最后通过创建 C2-C7 单键合并这些新的单突触盆地。第二步由一系列五个 SSD 描述，它们通过在 C12、C13、C3 和 C6 碳原子上创建四个伪自由基中心来重组 Int-a 内的电子密度。最后两个 SSD 通过合并先前域中形成的单突触盆地来处理两个 CC 键的形成。