The thermal isomerization of tricyclo[4.1.0.0^2, 7]heptene has been studied using computational chemistry with structures determined at the MCSCF level and energies at the MRMP2 level. Both the allowed conrotatory and forbidden disrotatory pathways have been elucidated resulting in cycloheptatriene isomers. Four reaction channels are available for the conrotatory pathway depending on which bond breaks first in the bicyclobutane moiety leading to enantiomeric pairs of (E,Z,Z)-1,3,5-cycloheptatriene and (Z,E,Z)-1,3,5-cycloheptatriene intermediates. The activation barrier is calculated to be 31.3 kcal·mol⁻¹ for two channels and 37.5 kcal·mol⁻¹ for the other two. The lower activation barrier leading to the (E,Z,Z)-1,3,5-cycloheptatriene enantiomeric pair is proposed to be due to resonance within the transition state. The same behavior was observed for the disrotatory pathway with activation barriers of 42.0 kcal·mol⁻¹ and 55.1 kcal·mol⁻¹ for the two channels, again with one transition state resonance stabilized. The barriers for trans double bond rotation of the intermediate cycloheptatrienes are determined to be 17.1 and 17.4 kcal·mol⁻¹, about 5 kcal·mol⁻¹ more than that for the seven carbon diene (E,Z)-1,3-cycloheptadiene. The electrocyclic ring closure of the trans cycloheptatrienes have been modeled and barriers determined to be 11.1 and 11.9 kcal·mol⁻¹ for the formation of bicyclo[3.2.0]hepta-2,6-diene. This structure was previously reported as the end product for thermolysis of the parent tricyclo[4.1.0.0^2, 7]heptene. The thermodynamically more stable cycloheptatriene can be formed from bicyclo[3.2.0]hepta-2,6-diene through a two step process with a calculated pseudo first-order barrier of 36.4 kcal·mol⁻¹. The trans-cycloheptatrienes reported herein are the first characterization of a small seven-membered ring triene with a trans double bond.

中文翻译：

---

从头开始研究三环[4.1.0.0 ^2，7 ]庚烯异构化的途径和障碍

三环[4.1.0.0 ^2，7 ]庚烯的热异构化已使用计算化学方法进行了研究，其结构在MCSCF水平确定，能量在MRMP2水平确定。阐明了允许的旋转路径和禁止的旋转路径，产生了环庚三烯异构体。四个反应通道可用于旋转路径，具体取决于哪个键首先在双环丁烷部分中断裂，从而导致（E，Z，Z）-1,3,5-环庚三烯和（Z，E，Z）-1对映体对， 3，5-环庚三烯中间体。计算出两个通道的激活势垒分别为31.3 kcal·mol ^-1和37.5 kcal·mol ^-1对于其他两个。提出导致（E，Z，Z）-1，3，5-环庚三烯对映异构体对的较低的活化势垒是由于在过渡态内的共振。对于旋转路径，观察到相同的行为，两个通道的激活势垒分别为42.0 kcal·mol ^-1和55.1 kcal·mol ^-1，再次稳定了一个过渡态共振。中间环庚烯的反式双键旋转的势垒确定为17.1和17.4 kcal·mol ^-1，比七个碳二烯（E，Z）-1,3-环庚二烯的势垒大约5 kcal·mol ^-1。反式环庚烯的电环闭环已经建模，并且势垒被确定为11.1和11.9 kcal·mol ^-1用于形成双环[3.2.0]庚-2,6-二烯。该结构先前被报道为母体三环[4.1.0.0 ^2、7 ]庚烯的热解终产物。热力学上更稳定的环庚三烯可以由双环[3.2.0]庚-2,6-二烯通过两步过程形成，计算出的拟一级反应势垒为36.4 kcal·mol ^-1。本文报道的反式环庚烯是具有反式双键的小七元环三烯的首次表征。