Takahashi Ikko, Fujita Takeshi, Shoji Noriaki, Ichikawa Junji
Division of Chemistry, Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
Chem Commun (Camb). 2019 Aug 14;55(63):9267-9270. doi: 10.1039/c9cc04152d. Epub 2019 Jul 10.
Transition metal-free hydroarylation of unactivated alkynes was achieved by combining a Brønsted acid catalyst and a two-phase solvent system consisting of 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP) and cyclohexane. This protocol is applicable to a wide variety of 2-alkynylbiaryls which leads to the synthesis of substituted phenanthrenes via 6-endo-selective ring closure. The biphasic system achieves highly efficient ring closure by appropriate separation of cationic intermediates from neutral compounds. The vinyl carbocation intermediates are stabilised in the HFIP phase, while the substrates and products are distributed in the cyclohexane phase to suppress intermolecular side reactions.
通过将布朗斯特酸催化剂与由1,1,1,3,3,3-六氟-2-丙醇（HFIP）和环己烷组成的两相溶剂体系相结合，实现了未活化炔烃的无过渡金属氢芳基化反应。该方法适用于多种2-炔基联芳基化合物，通过6-内型选择性环化反应合成取代菲。该双相体系通过将阳离子中间体与中性化合物适当分离，实现了高效的环化反应。乙烯基碳正离子中间体在HFIP相中得到稳定，而底物和产物则分布在环己烷相中，以抑制分子间的副反应。
