Division of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
Chem Commun (Camb). 2021 Sep 4;57(68):8500-8503. doi: 10.1039/d1cc03453g. Epub 2021 Aug 5.
Transition-metal-free acid-promoted biaryl construction was achieved via intermolecular C-F/C-H cross-coupling. By treating 2-fluorobenzofurans with arenes in the presence of AlCl, 2-arylbenzofurans were obtained. This protocol was successfully applied to the short-step orthogonal synthesis of a bioactive 2-arylbenzofuran natural product, which allows independent transformations of C-F and C-Br bonds. Mechanistic studies indicated that α-fluorine-stabilized carbocations, generated via the protonation of 2-fluorobenzofurans, served as key intermediates. The Friedel-Crafts-type C-C bond formation between the α-fluorocarbocations and arenes, followed by hydrogen fluoride elimination, afforded 2-arylbenzofurans.
无过渡金属参与的酸促进的联芳构建是通过分子间的 C-F/C-H 交叉偶联实现的。通过在 AlCl 的存在下用芳基处理 2-氟苯并呋喃，得到 2-芳基苯并呋喃。该方案成功地应用于生物活性 2-芳基苯并呋喃天然产物的短步正交合成，该方法允许 C-F 和 C-Br 键的独立转化。机理研究表明，通过质子化 2-氟苯并呋喃生成的α-氟稳定的碳正离子是关键中间体。α-氟碳正离子与芳基之间发生 Friedel-Crafts 型 C-C 键形成，随后消除氟化氢，得到 2-芳基苯并呋喃。
