Yamabe Shinichi, Minato Tsutomu, Ishiwata Akihiro, Irinamihira Osamu, Machiguchi Takahisa
Department of Chemistry, Nara University of Education, Takabatake-cho, Nara 630-8528, Japan.
J Org Chem. 2007 Apr 13;72(8):2832-41. doi: 10.1021/jo062256e. Epub 2007 Mar 17.
A benzyne-tropothione reaction was studied experimentally and computationally. Three isomeric products were detected by a careful experiment using two benzyne sources. The three equimolar products were identified. The expected symmetry-allowed [4+2] or [8+2] cycloadduct was not detected. In order to explain the unexpected products, density functional calculations and complete active space self-consistent field (CASSCF) calculations were carried out. The benzyne is, first, added to the tropothione via one-center C-S bond formation. Then a singlet biradical intermediate is formed. In the biradical, an alpha hydrogen atom of the tropothione moiety is moved to the benzyne moiety. A closed-shell intermediate is generated. This allene-type intermediate is isomerized to the second intermediate. The intramolecular proton shift in the latter leads to the three products. The biradical character of the benzyne has a key role in the present reaction and was discussed in reference to other benzyne reactions.
对苯炔与硫环辛四烯的反应进行了实验和计算研究。通过使用两种苯炔源进行的仔细实验检测到了三种异构体产物。鉴定出了这三种等摩尔产物。未检测到预期的对称性允许的[4+2]或[8+2]环加成产物。为了解释这些意外产物，进行了密度泛函计算和完全活性空间自洽场（CASSCF）计算。首先，苯炔通过单中心C-S键形成加成到硫环辛四烯上。然后形成一个单线态双自由基中间体。在双自由基中，硫环辛四烯部分的一个α氢原子转移到苯炔部分。生成一个闭壳中间体。这种丙二烯型中间体异构化为第二种中间体。后者中的分子内质子转移导致了这三种产物。苯炔的双自由基特性在本反应中起关键作用，并参考其他苯炔反应进行了讨论。
