title: A computational investigation on the sequential rearrangement mechanism of 2-allyl-2,4,5-hexatrienaldehyde involving [1,5]-hydrogen migration and 8pi-electrocyclization.
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.
authors: Department of Chemistry, Sichuan University, Chengdu 610064, China.
authors: Yuanqiang
authors: Y
authors: Zhu
authors: Yong
authors: Y
authors: Guo
authors: Lidong
authors: L
authors: Zhang
authors: Daiqian
authors: D
authors: Xie