硫代双烯酮与异氰酸环加成反应的理论研究

采用从头算ＲＨＦ／６－３１Ｇ方法研究了硫代双烯酮与异氰酸之间两种可能的环加成反应的机理，并对反应各驻点进行了电子密度拓扑分析研究．结果表明，这两个生成不同四元杂环产物的平行反应均为非同步的协同反应，但两个反应进行的难易程度不同，形成硫氮杂环的反应更容易一些，而形成氮杂环反应的产物在热力学上更稳定一些

Theoretical Studies on the Mechanism of the CycloadditionReaction between Thioketene and Isocyanic Acid

The cycloaddition reactions of thioketene and isocyanic acid forming four-membered ring products were studied by means of ab initio RHF/6-31G* method. All the geometries of the stationary points on the reaction path have been optimized by energy gradient technique, and all the transition states were characterized by vibration frequency analysis. These two parallel reactions are all concerted but nonsynchronous, taking place through twisted or planar four-membered cyclic transition states. The activation barriers were calculated to be 150.41 and 109.95 kJmol-1 respectively for two parallel reactions (1) and (2), which means that the reaction (2) is favorable. In addition, Bader type electron density topological analysis was used to study the electronic structure of stationary points for reactions (1) and (2).