School of Chemistry and Chemical Engineering, University of Jinan, Jinan, Shandong 250022, People's Republic of China.
J Mol Model. 2012 Nov;18(11):4787-95. doi: 10.1007/s00894-012-1485-1. Epub 2012 Jun 15.
The mechanism of the cycloaddition reaction between singlet silylene silylene (H₂Si=Si:) and acetaldehyde has been investigated with CCSD(T)//MP2/6-31G* and CCSD(T)//MP2/6-31G** method, from the potential energy profile, we could predict that the reaction has three competitive dominant reaction pathways. The present rule of this reaction is that the 3p unoccupied orbital of the Si: atom in silylene silylene (H₂Si=Si:) inserts on the π orbital of acetaldehyde from oxygen side, resulting in the formation of an intermediate. Isomerization of the intermediate further leads to the generation of a four-membered ring silylene (the H₂Si-O in the opposite position). In addition, the [2 + 2] cycloaddition reaction of the two π-bonds in silylene silylene and acetaldehyde generates another four-membered ring silylene (the H₂Si-O in the syn-position). Because of the unsaturated property of Si: atom in the two four-membered ring silylenes, they could further react with acetaldehyde, resulting in the generation of two spiro-heterocyclic ring compounds with Si. Simultaneously, the ring strain of the four-membered ring silylene (the H₂Si-O in the syn-position) makes it isomerize to a twisted four-membered ring product.
用 CCSD(T)//MP2/6-31G* 和 CCSD(T)//MP2/6-31G** 方法研究了单线态硅烯硅烯（H₂Si=Si:）和乙醛之间环加成反应的机理。从势能面来看，我们可以预测该反应有三种具有竞争优势的反应途径。该反应的现有规则是，硅烯硅烯（H₂Si=Si:）中 Si:原子的 3p 空轨道从氧侧插入乙醛的π轨道，形成中间体。中间体的异构化进一步导致四元环硅烯（对位的 H₂Si-O）的生成。此外，硅烯硅烯和乙醛的两个π键的[2+2]环加成反应生成另一个四元环硅烯（顺式的 H₂Si-O）。由于两个四元环硅烯中 Si:原子的不饱和性质，它们可以进一步与乙醛反应，生成两个具有 Si 的螺杂环化合物。同时，四元环硅烯（顺式的 H₂Si-O）的环张力使其异构化为扭曲的四元环产物。
