摘要/Abstract
利用自由基参与的远端炔基迁移策略实现了非活化烯烃的炔基化反应. 以磺酰氯为试剂, 在可见光促进下形成三氟甲基自由基或芳基(烷基)磺酰基自由基, 随后加成到非活化烯烃上, 生成烷基自由基中间体, 继而诱导远端炔烃的分子内迁移, 得到三氟甲基炔基化或磺酰基炔基化产物. 该方法具有条件温和、底物易得以及官能团兼容性广等优点.
关键词: 炔基化, 三氟甲基化, 磺酰化, 烯烃双官能团化, 官能团迁移
Radical-mediated difunctionalization of alkenes through the remote functional group migration (FGM) process paves an ingenious avenue for simultaneous cleavage and reconstruction of C—C bonds. Recently, our group has systematically disclosed the strategy of remote FGM for radical-mediated difunctionalization of unactivated alkenes. A portfolio of functional groups including cyano, heteroaryl, alkynyl, oximino, and carbonyl showcase the migratory aptitude, leading to new C—C bonds under radical conditions. Meanwhile, a series of other chemical bonds such as C—C, C—N, C—P, C—Si, and C—S are readily constructed in the reaction. Considering the synthetic utility and flexible transformation of alkynes, the radical alkynylation of unactivated alkenes via remote alkynyl migration we firstly reported provides an efficient approach for the incorporation of alkynes and has received considerable attention. On the other hand, fluorine- and sulfonyl-containing molecules play vital roles in organic and medicinal chemistry owing to their important chemical and physical characters. Therefore, the concomitant introduction of an alkynyl and a trifluoromethyl/sulfonyl group into one molecule is of great synthetic value. Herein we report a useful method for carbo-trifluoroalkylation/sulfonylation of unactivated olefins. The addition of extrinsic radical to alkene triggers the intramolecular FGM via a five-membered transition state along with a cascade of bond fission and formation. The typical procedure is as follows: a mixture of propargyl alcohol 1, sulfonyl chloride, fac-Ir(ppy)3, and base is loaded in a flame-dried reaction vial which is subjected to evacuation/flushing with nitrogen three times. Solvent is added to the mixture via syringe and the mixture is then stirred at 25 ℃ until the starting material is consumed monitored by TLC. The mixture is concentrated, and purified by flash column chromatography on silica gel (eluent: petroleum ether/ethyl acetate) to give the product.
Key words: alkynylation, trifluoromethylation, carbosulfonylation, alkene difunctionalization, functional group migration
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