Revisiting Hydrogen [1,5] Shifts in Cyclopentadiene and Cycloheptatriene as Bimolecular Reactions.
Revisiting Hydrogen [1,5] Shifts in Cyclopentadiene and Cycloheptatriene as Bimolecular Reactions.
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DOI：
10.1021/ct0500646
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发表时间：
2005-08
影响因子：
5.5
通讯作者：
S. Yamabe;N. Tsuchida;S. Yamazaki
中科院分区：
文献类型：
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作者：
S. Yamabe;N. Tsuchida;S. Yamazaki
氢[1，5]转移是周环反应，通常发生在1，3-戊二烯中。然而，由于结构的限制，1，3-环戊二烯和1，3，5-环庚三烯的对称性热反应受到很大的势垒限制，用密度泛函理论(B3LYP/6-31G*)计算的ΔU(‡)=+26.9kcal/m ol和ΔU(‡)=+37.5kcal/m o l。这一理论研究表明，exo[4+2]和[6+4]环加成二聚体涉及新的氢转移通道。氢迁移后得到单中心加合物，经过Cope重排生成第二个单中心加合物。从中间体出发，以[1，5]迁移的氢为原料，反转路线得到CPD和CHT。文中还讨论了周环反应中环加成反应与[1，5]和[3，3]Sigma重排的关系。
Hydrogen [1,5] shifts are pericyclic reactions and take place typically in 1,3-pentadiene. However, because of structure restriction, the symmetry-allowed thermal reactions of 1,3-cyclopentadiene (CPD) and 1,3,5-cycloheptatriene (CHT) suffer large energy barriers, ΔU(‡) = +26.9 kcal/mol and ΔU(‡) = +37.5 kcal/mol by density-functional theory (B3LYP/6-31G*) calculations, respectively. This theoretical study has shown that exo [4+2] and [6+4] cycloadduct dimers involve novel hydrogen-shift channels. After hydrogen migration, one-center adducts are obtained, which undergo Cope rearrangements leading to the second one-center adducts. From the intermediates, reverse routes lead to CPD and CHT with [1,5] migrated hydrogens. A correlation between cycloadditions and [1,5] and [3,3] sigmatropic rearrangements in pericyclic reactions is also discussed.