Organic Pharmaceutical Chemistry, Department of Medicinal Chemistry, Uppsala University, BMC, P.O. Box 574, SE-751 23 Uppsala, Sweden.
Chemistry. 2012 Apr 10;18(15):4714-22. doi: 10.1002/chem.201102678. Epub 2012 Feb 28.
The formation of an atypical, saturated, diarylated, Heck/Suzuki, domino product produced under oxidative Heck reaction conditions, employing arylboronic acids and a chelating vinyl ether, has been investigated by DFT calculations. The calculations highlight the crucial role of 1,4-benzoquinone (BQ) in the reaction. In addition to its role as an oxidant of palladium, which is necessary to complete the catalytic cycle, this electron-deficient alkene opens up a low-energy reaction pathway from the post-insertion σ-alkyl complex. The association of BQ lowers the free-energy barrier for transmetallation of the σ-alkyl complex to create a pathway that is energetically lower than the oxidative Heck reaction pathway. Furthermore, the calculations showed that the reaction is made viable by BQ-mediated reductive elimination and leads to the saturated diarylated product.
DFT 计算研究了在氧化 Heck 反应条件下，使用芳基硼酸和螯合乙烯基醚，形成非典型的、饱和的、二芳基化的 Heck/Suzuki 级联产物。计算突出了 1,4-苯醌 (BQ) 在反应中的关键作用。除了作为钯的氧化剂（这是完成催化循环所必需的）之外，这种缺电子烯烃从插入后的 σ-烷基配合物开辟了一条低能量的反应途径。BQ 的缔合降低了 σ-烷基配合物的转金属化的自由能势垒，从而形成一条能量低于氧化 Heck 反应途径的途径。此外，计算表明，BQ 介导的还原消除使反应成为可能，并导致饱和的二芳基化产物。
