Yamabe S., Okumoto S., Hayashi T.
Matsushita Electric Works, Ltd., 1048, Kadoma, Osaka 571, Japan.
J Org Chem. 1996 Sep 6;61(18):6218-6226. doi: 10.1021/jo9522419.
Ab initio calculations were performed for eight Claisen rearrangements, eqs 1-8. Transition-state (TS) structures of [3,3] sigmatropic rearrangements of reactions 1-4 are similar, but their activation energies (E(a)'s) are different, E(a)(1) < E(a)(2) and E(a)(3) < E(a)(4). From the intermediate of reaction 3, a hydrogen is moved intermolecularly to form the product, o-allyl phenol. The lower reactivities of reactions 2 and 4 relative to reactions 1 and 3 are ascribed to large endothermicities in the sigmatropic rearrangements, respectively. Chair-type transition states are more favorable than boat-type transition states in reactions 1-4. The allyl group is released from the in-plane C-X (X = O or N) sigma bond and is captured by the pi-type lone-pair electrons. The sulfur- and phosphorus-containing rearrangements, reactions 5-8, are computed to have smaller activation energies but are to be less exothermic than those of oxgyen- and nitrogen-containing rearrangements.
对八个克莱森重排反应（方程式1 - 8）进行了从头算。反应1 - 4的[3,3] - 迁移重排的过渡态（TS）结构相似，但它们的活化能（E(a)）不同，E(a)(1) < E(a)(2)且E(a)(3) < E(a)(4)。从反应3的中间体开始，一个氢原子通过分子间迁移形成产物邻烯丙基苯酚。反应2和4相对于反应1和3的较低反应活性分别归因于迁移重排中的较大吸热性。在反应1 - 4中，椅型过渡态比船型过渡态更有利。烯丙基从平面内的C - X（X = O或N）σ键中脱离，并被π型孤对电子捕获。含硫和含磷的重排反应（反应5 - 8）经计算具有较小的活化能，但放热比含氧化合物和含氮重排反应少。
