Bloom Steven, Bume Desta Doro, Pitts Cody Ross, Lectka Thomas
Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (USA).
Chemistry. 2015 May 26;21(22):8060-3. doi: 10.1002/chem.201501081. Epub 2015 Apr 15.
To expand upon the recent pioneering reports of catalyzed sp(3) C-H fluorination methods, the next rational step is to focus on directing "radical-based fluorination" more effectively. One potential solution entails selective C-C bond activation as a prelude to selective fluorination. Herein, we report the tandem photocatalyzed ring-opening/fluorination reactions of cyclopropanols by 1,2,4,5-tetracyanobenzene (TCB) and Selectfluor to afford a process tantamount to site-selective β-fluorination of carbonyl-containing compounds. This new approach provides a synthetically mild and operationally simple route to otherwise difficult-to-prepare β-fluorinated products in good yields and with good-to-excellent regioselectivity. Remarkably, substrates that contain other usually reactive (e.g., benzylic) sites undergo ring-opening fluorination preferably. The versatility of this method to give cyclic β-fluorides from tertiary cyclopropanols and γ-fluoro alcohols is also highlighted.
为进一步拓展近期关于催化sp(3) C-H氟化方法的开创性报道，接下来合理的步骤是更有效地聚焦于导向“基于自由基的氟化”。一种潜在的解决方案是将选择性C-C键活化作为选择性氟化的前奏。在此，我们报道了环丙醇与1,2,4,5-四氰基苯（TCB）和Selectfluor的串联光催化开环/氟化反应，以提供一种相当于对含羰基化合物进行位点选择性β-氟化的过程。这种新方法提供了一条合成温和且操作简单的路线，能够以良好的产率和良好至优异的区域选择性制备其他难以制备的β-氟化产物。值得注意的是，含有其他通常具有反应性的（例如苄基）位点的底物优先发生开环氟化反应。该方法从叔环丙醇生成环状β-氟化物以及生成γ-氟代醇的通用性也得到了突出体现。
