Synthesis and Reactions of Novel Boron-containing Double-bond Compounds by Taking Advantage of Steric Protection

由于含硼双键化合物的高活性，合成稳定的含硼双键化合物的报道很少。另一方面，我们利用有效的空间位阻保护基2，4，6-三[双（三甲基硅基）甲基]苯基（Tbt）的动力学稳定作用，成功地合成了高活性的含硼双键化合物。本课题作为第13族元素多键化合物化学研究的第一步，利用Tbt基团的优势，设计合成了稳定的硫氧硼烷1 [TbtB=S]和二硼烯2 [TbtB=BTbt]，并成功地合成了第一个稳定的二巯基硼烷3 [TbtB（SH）_2]。3与4、14或15族金属二卤化物反应，得到相应的1，3，2，4-二硫杂硼杂环戊烷衍生物4，并系统地研究了它们的结构和性质的差异。1，3，2，4-二硫杂锡硼杂环己烷4a [TbtBS_2SnPh_2]通过[2+2]逆环加成反应生成了预期的硫氧硼烷1。硫代硼烷1与1，3-二烯反应得到相应的[2+4]环加成物5，后者在加热条件下通过[2+4]逆环加成反应生成1，4a与二甲基亚砜反应得到第一个稳定的硫代硼烷-路易斯碱配合物6 [TbtB=O-DMSO]。我们还成功地合成了相应的1，3，2，4-二硒杂锡钠硼烷衍生物，并合成了硒代氧硼烷[TbtB=Se]。我们相信，在本项目所获得的硼-16族元素双键化合物的基础上，可以实现2的合成。

Very little is reported for the synthesis of stable boron-containing double-bond compounds because they are highly reactive, On the other hand, we have succeeded in the synthesis of highly reactive species by taking advantage of kinetic stabilization using effective steric protection group, 2,4,6-tris[bis(trimethylsilyl)-methyl]phenyl (Tbt) group. In this project, as the first stage for the development of the chemistry of multiple-bonded compounds containing group 13 elements, we planned the synthesis of stable thioxoborane 1 [TbtB=S] and diborene 2 [TbtB=BTbt] by taking advantage of Tbt group leading to the elucidation of their properties.We succeeded in the synthesis of the first stable dimercaptoborane 3 [TbtB(SH)_2]. Reactions of 3 with various group 4, 14 or 15 metal dihalides gave the corresponding 1,3,2,4-dithiametallaboretane derivatives 4, and the differences in their structures and properties were systematically investigated. Thermolysis of 1,3,2,4-dithiastannaboretane 4a [TbtBS_2SnPh_2] resulted in the formation of the expected thioxoborane 1 via [2+2]retrocycloaddition. Thioxoborane 1 reacted with 1 , 3-dienes to afford the corresponding [2+4]cycloadducts 5, which was found to regenerate 1 via [2+4]retrocycloaddition on heating.Reaction of 4a with dimethylsulfoxide (DMSO) gave the oxoborane-DMSO complex 6 [TbtB=O-DMSO], the first stable oxoborane-Lewis base complex. Thermolysis of 6 resulted in the formation of the corresponding oxoborane [TbtB=O].We have also succeeded in the generation of selenoxoborane [TbtB=Se] by thermolysis of the corresponding 1,3,2,4-diselenastannnaboretane derivative.Although we have not succeeded in the synthesis of diborene 2, the other target molecule in this project, yet, we believe that the synthesis of 2 can be achieved on the basis of the knowledge about boron-group 16 element double-bond compounds obtained in this project.