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

以顺式-1，2-二硫代二钠为氧化剂，成功地合成了环-1，5-二烯的3个碳上硫原子取代的四硫杂环-3，7-二烯-四硫杂环辛烷1和八硫环十六烯-3，7，11，15-四烯-2。1的X-射线衍射结构为扭曲结构(近D_2对称性)，2的晶体结构为笼状结构(近D_2对称性)，具有空穴。笼状结构表明，化合物2有望成为具有两种配位(烯烃的pi电子和硫原子上的孤对)的新包合物。在从头算的基础上，对1进行了比较研究。计算结果表明，1的扭转构象具有最低的势能，最稳定的构型与1的X-射线结构吻合较好。此外，1的稳定构型与相应的碳类似物(环辛二烯)不同。化合物1热稳定，在对二甲苯中回流3h也不分解，但化合物1在乙腈/氯仿等极性溶剂中，即使在室温下也发生变化，以较高的产率得到扩环产物2。化合物1也被发现对辐射不稳定，甚至对房间光线也是如此。1在苯溶液中辐射，与双环化合物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.