Department of Chemistry, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan.
J Phys Chem A. 2010 Nov 4;114(43):11807-13. doi: 10.1021/jp105860n.
The mechanisms of the Myers-Saito cyclization and the Schmittel cyclization of hepta-1,2,4-triene-6-yne are studied by ab initio multireference MO methods (CASSCF and MRMP2 methods). For the Myers-Saito cyclization, two transition states with C(s) and C₁ symmetries are located. The transition state with C1 symmetry is only 1.5 kcal/mol lower in energy than that with C(s) symmetry at the MRMP2 calculation level. The obtained activation energy at the transition state with C₁ symmetry and the reaction energy are 16.6 and 16.2 kcal/mol exothermic, respectively. For the Schmittel cyclization, two transition states with C(s) and C₁ symmetry are also obtained. The transition state with C₁ symmetry is 7.9 kcal/mol lower in energy than that with C(s) symmetry. The transition state with C₁ symmetry for Schmittel cyclization is 6.7 kcal/mol higher in energy than that for the Myers-Saito cyclization. The reaction mechanisms are analyzed by a CiLC-IRC method. The interactions of orbitals for the Myers-Saito and Schmittel cyclizations can be distinguished.
通过从头算多参考 MO 方法（CASSCF 和 MRMP2 方法）研究了七元 1,2,4-三烯-6-炔的迈尔斯-赛托环化和施密特环化的机理。对于迈尔斯-赛托环化，定位到具有 C(s) 和 C₁对称性的两个过渡态。在 MRMP2 计算水平下，C₁对称过渡态的能量仅比 C(s)对称过渡态低 1.5 kcal/mol。在 C₁对称过渡态的获得的活化能和反应能分别为 16.6 和 16.2 kcal/mol 放热。对于施密特环化，也得到了具有 C(s)和 C₁对称性的两个过渡态。C₁对称过渡态的能量比 C(s)对称过渡态低 7.9 kcal/mol。对于施密特环化的 C₁对称过渡态，其能量比迈尔斯-赛托环化的 C₁对称过渡态高 6.7 kcal/mol。通过 CiLC-IRC 方法分析反应机理。可以区分迈尔斯-赛托和施密特环化的轨道相互作用。
