Synthesis and Reactivity of Cyclic Unsaturated Compounds Substituted by 16 Group Elements

以顺式1，2-二硫醇二钠为原料，通过氧化反应成功地合成了环辛-1，5-二烯的sp^3碳上被硫原子取代的四硫辛（四硫环辛-3，7-二烯）1和八硫环十六碳-3，7，11，1,5-四烯2。1的X射线结构呈扭曲型（近D_2对称），2的晶体结构呈笼形（近D_<2d>对称），并带有空腔。笼状结构表明化合物2有望成为一种具有两种配位位置（烯烃的π电子和硫原子上的孤对电子）的新型包合物。1的比较也进行了研究的基础上从头算分子轨道计算。1的扭曲构象被计算为在所有构象中具有最低的势能，并且最稳定的几何形状与1的X射线结构显示出良好的一致性。此外，稳定的几何形状被发现之间的1和相应的碳类似物（环辛-1，5-二烯）是不同的。四硫菌素1是热稳定的，即使在对二甲苯中3小时后也没有观察到分解。然而，化合物1在极性溶剂如乙腈/氯仿溶液中发生变化，即使在室温下也以良好的产率得到扩环产物2。还发现化合物1对辐射不稳定，甚至对室内光也不稳定。1在苯溶液中辐照，与双环化合物一起形成橡胶状黄色聚合物。

Tetrathiocin (tetrathiacycloocta-3,7-diene) 1, substituted by sulfur atoms at the sp^3 carbons of cycloocta-1,5-diene, and octathiacyclohexadeca-3,7,11,15-tetraene 2 were synthesized successfully by oxidation of cis-disodium ethene-1,2-dithiolate. The X-ray structure of 1 showed the twist form (nearly D_2 symmetry), and the crystal structure of 2 was found to have cage geometry (nearly D_<2d> symmetry) possessing a cavity. The cage structure indicates that the compound 2 is expected to become a new inclusion compound with two types of coordination site (pi-electrons of the olefins and lone pairs on the sulfur atoms). A comparison of 1 was also studied based on ab initio MO calculations. The twist conformer of 1 was calculated to have the lowest potential energy among all the conformers, and the most stable geometry showed good agreement with the X-ray structure of 1. Furthermore, stable geometries were found to be different between 1 and corresponding carbon analogue (cycloocta-1,5-diene). Tetrathiocin 1 was thermally stable and no decomposition was observed even in refluxing p-xylene after 3 h. However, compound 1 changed in polar solvent, such as acetonitrile/chloroform solution, even at room temperature to give the ring expansion product 2 in good yield. Compound 1 was also found to be unstable toward irradiation, even room light. Irradiation of 1 in a benzene solution, a rubber-like yellow polymer was formed together with bicyclic compound.