摘要/Abstract

利用自由基参与的官能团迁移策略实现了非活化烯烃的三氟甲硫基化反应.通过AgSCF₃和K₂S₂O₈相互作用产生的三氟甲硫基自由基与非活化烯烃反应，继而诱导远端含有碳氮双键官能团（杂芳基、亚胺）的分子内迁移，从而实现非活化烯烃的三氟甲硫基化反应.该转化具有反应条件温和、产物收率高、官能团兼容性广及区域选择性单一等特点，对具有不同电性和位阻的底物具有较好的适用性，高效构建了一系列含有三氟甲硫基的烷烃酮化合物.
关键词: 烯烃双官能团化, 三氟甲硫基, 迁移反应, 自由基反应, 杂芳基
Radical-mediated C-SCF₃ bond formation via the addition of SCF₃ radical to alkenes has become an efficient strategy for the construction of alkyl trifluoromethylthioethers. However, the scope of alkenes is largely limited to activated alkenes in which the presence of adjacent carbonyl or aryl group is required to stabilize the alkyl radical intermediates by p-π conjugation. A few cases involving trifluoromethylthiolation of unactivated olefins have been reported, but in these reactions only a single functional group is incorporated to alkenes. The radical difunctionalization of unactivated olefins remains challenging and has received less attention. Recently, we established a new protocol to realize the radical difunctionalization of alkenes through intramolecularly distal functional group migration. This tactic provides a useful and elegant tool for the elusive functionalization of unactivated olefins. A portfolio of groups such as cyano, heteroaryl, imino, aldehyde, and alkynyl can be readily migrated in the transformation. Herein, we disclose an efficient and practical approach for the trifluoromethylthiolation of unactivated olefins based on the intramolecular migration of heteroaryl and imino groups. The migration is triggered by the addition of SCF₃ radical, which is generated from the mixture of AgSCF₃ and K₂S₂O₈at room temperature, to alkenes. The reaction demonstrates a high functional group compatibility and broad substrate scope. A variety of nitrogen-containing five- and six-membered heteroaryl as well as imino groups are readily migrated, affording the synthetically valuable alkyl trifluoromethylthioether compounds in good yields. The typical procedure is as follows: a mixture of tertiary alcohol (0.2 mmol), AgSCF₃(0.3 mmol), and K₂S₂O₈(0.6 mmol) is loaded in a flame-dried reaction vial which is subjected to evacuation/flushing with nitrogen three times. Dry DMF (2.0 mL) is added to the mixture via syringe, and the mixture is then stirred at room temperature until the starting material is consumed which is determined by TLC. The mixture is extracted with ethyl acetate (10 mL×3). The combined organic extracts are washed with brine, dried over Na₂SO₄, filtered, concentrated, and purified by flash column chromatography on silica gel (eluent: petroleum ether/ethyl acetate) to give the desired product.
Key words: alkene difunctionalization, trifluoromethylthiolation, migration reaction, radical reaction, heteroaryl


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