Tactics for Probing Aryne Reactivity: Mechanistic Studies of Silicon-oxygen Bond Cleavage During the Trapping of (HDDA-generated) Benzynes by Silyl Ethers.
Tactics for Probing Aryne Reactivity: Mechanistic Studies of Silicon-oxygen Bond Cleavage During the Trapping of (HDDA-generated) Benzynes by Silyl Ethers.
复制标题
DOI：
10.1039/c3sc53014k
复制
发表时间：
2014-02
期刊：
影响因子：
8.4
通讯作者：
Wang T
中科院分区：
文献类型：
--
作者：
Hoye TR;Baire B;Wang T
我们报告了通过侧甲硅烷基醚基团捕获热（HDDA）生成的苯炔衍生物的机制，这导致一对苯炔Csp-氢化碳原子净插入到硅-氧西格玛键中。使用对称、双标记的双甲硅烷基醚底物的交叉实验证实该反应本质上是单分子的。使用涉及分子内或分子间二氢转移时钟反应（分别来自 TIPS 异丙基或环辛烷内部）与甲硅烷基醚环化的竞争实验来获得更多见解。我们评估了甲硅烷基醚捕获基团的空间体积和所形成的环醚的环尺寸的影响（呋喃与吡喃）。这些类型的竞争实验可以确定各种产品决定步骤的相对速率。这在以前很少是可能的，因为芳基的形成通常是限速的，使得探测后续捕获反应的动力学变得具有挑战性。使用溶剂效应（介质的极性）和计算研究来探讨 Si-O 插入的逐步路径与协调路径的问题。
We report mechanistic aspects of the trapping of thermally (HDDA) generated benzyne derivatives by pendant silyl ether groups, which results in net insertion of the pair of benzyne Csp-hydribized carbon atoms into the silicon–oxygen sigma bond. Cross-over experiments using symmetrical, doubly labeled bis-silyl ether substrates established that the reaction is unimolecular in nature. Competition experiments involving either intramolecular or intermolecular dihydrogen transfer clock reactions (from within a TIPS isopropyl group or cyclooctane, respectively) vs. the silyl ether cyclization were used to gain additional insights. We evaluated effects of the steric bulk of the silyl ether trapping group and of the ring-size of the cyclic ether being formed (furan vs. pyran). These types of competition experiments allow the relative rates of various product-determining steps to be determined. This previously has only rarely been possible because aryne formation is typically rate-limiting, making it challenging to probe the kinetics of subsequent trapping reactions. Solvent effects (polarity of the medium) and computational studies were used to probe the question of stepwise vs. concerted pathways for the Si–O insertion.