A computational investigation on the sequential rearrangement mechanism of 2-allyl-2,4,5-hexatrienaldehyde involving [1,5]-hydrogen migration and 8pi-electrocyclization |
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Authors: | Zhu Yuanqiang Guo Yong Zhang Lidong Xie Daiqian |
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Institution: | Department of Chemistry, Sichuan University, Chengdu 610064, China. |
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Abstract: | The sequential rearrangement reaction mechanism of the 2-allyl-2,4,5-hexatrienaldehyde has been studied at the unrestricted Becke three-parameter hybrid functional combined with Lee-Yang-Parr correlation functional (UB3LYP)/6-31G**, Complete Active Space Self-Consistent Field (CAS (8,8))/6-31G**, Configuration Interaction with Single and Double Excitations (CISD)//UB3LYP/6-31G** and the second-order perturbation theory based on the CASSCF reference wave function (CASPT2)//CAS(8,8)/6-31G** levels. Two pathways have been found to be involved for this reaction. The first pathway includes four processes of the rotation of the C3--C4 single bond, the stepwise 2 + 2] cycloaddition, the 1,5]-hydrogen migration, and the ring opening isomerization, while the second pathway undergoes only two processes of the 1,5]-hydrogen migration and the 8pi-electrocyclization. The calculation results indicate that the second pathway is favorable, in good agreement with the recent experimental observation. The whole reaction is stepwise and strong exothermic. |
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Keywords: | reaction mechanism thermal [2 + 2] cycloaddition electrocyclization density functional theory [1 5]‐hydrogen migration |
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