Mao Zhifeng, Huang Fei, Yu Haifeng, Chen Jiping, Yu Zhengkun, Xu Zhaoqing
Chemistry. 2014 Mar 17;20(12):3439-45. doi: 10.1002/chem.201305069.
The functionalization of internal olefins has been a challenging task in organic synthesis. Efficient CuII-catalyzed trifluoromethylation of internal olefins, that is, α-oxoketene dithioacetals, has been achieved by using Cu(OH)2 as a catalyst and TMSCF3 as a trifluoromethylating reagent. The push-pull effect from the polarized olefin substrates facilitates the internal olefinic C-H trifluoromethylation. Cyclic and acyclic dithioalkyl α-oxoketene acetals were used as the substrates and various substituents were tolerated. The internal olefinic C-H bond cleavage was not involved in the rate-determining step, and a mechanism that involves radicals is proposed based on a TEMPO-quenching experiment of the trifluoromethylation reaction. Further derivatization of the resultant CF3 olefins led to multifunctionalized tetrasubstituted CF3 olefins and trifluoromethylated N-heterocycles.
内烯烃的官能团化一直是有机合成中的一项具有挑战性的任务。通过使用Cu(OH)₂作为催化剂和TMSCF₃作为三氟甲基化试剂，实现了高效的CuII催化的内烯烃（即α-氧代烯酮二硫代缩醛）的三氟甲基化反应。来自极化烯烃底物的推拉效应促进了内烯烃C-H的三氟甲基化反应。环状和非环状二硫代烷基α-氧代烯酮缩醛被用作底物，并且各种取代基均能耐受。内烯烃C-H键的断裂不参与速率决定步骤，并且基于三氟甲基化反应的TEMPO猝灭实验提出了一种涉及自由基的机理。所得CF₃烯烃的进一步衍生化导致了多官能化的四取代CF₃烯烃和三氟甲基化的N-杂环化合物。
