顺-8-三甲基锡烷基-6-辛烯醛分子内环化反应立体选择性的理论研究

用密度泛函方法在B3LYP/6-31G^*水平上研究了顺-8-三甲基锡烷基-6-辛烯醛分子内环化反应的机理,通过振动分析和内禀反应坐标对过渡态进行了确认,解析了三种反应途径.结果表明,反应具有很强的立体选择性,虽然-OSn(CH₃)₃和-C₂H₃基团均处于环的平伏位,是最稳定的产物构型,但是主要产物是经过活化能最低,且具有两个六元环椅式构象的过渡态形成的,主要产物中-OSn(CH₃)₃基团处于环的直立位.该结果与实验事实一致.

Theoretical Studies on the Intramolecular Cyclization of (Z)-8-(Trimethylstannyl)oct-6-enal

The intramolecular cyclization of (Z)-8-(trimethylstannyl)oct-6-enal were studied by using the density functional method at the B3LYP/6-31G^*level.The structures and energies of the stationary points were calculated to produce the activation barriers.The transition states were testified by using vibration analysis and IRC calculations.Three reaction pathways were analyzed.All the reactions are the exothermic reations and the concerted reaction processes which have only one double-six-membered transition state dominated by the Cl-C6 vibration.Each of the reactions progresses with the bond formation of Sn10-O9 and C1-C6, the bond breaking of C8-Sn10 and the migration of the diene double bond to form the six-membered cyclic product.The results show that the reaction occurs with a high stereoselectivity.The product, in which both-OSn(CH₃)₃and-C₂H₃moieties are at the equatorial position, is the most stable one among three reactions, whereas the mainly product is obtained through the double-six-membered chairlike conformational transition state with the lowest barrier height.ThiSISIn excellent {agreement} with the experimental results.