摘要/Abstract
报道了以乙腈为氰甲基源，LiHMDS为碱，在室温下通过氰甲基化α-（三氟甲基）芳基乙烯，合成了一系列氰基化的偕二氟烯烃.该方法具有反应条件相对温和、反应迅速、操作简单、官能团兼容性较好、收率较高等优点.
关键词: α-(三氟甲基)芳基乙烯, 乙腈, 氰甲基化, 氰基化偕二氟芳基乙烯
Nitriles are important structural motifs found in agrochemicals, pharmaceuticals, and natural products. Furthermore, nitriles are versatile synthetic precursors for organic synthesis because they can be easily converted into various functionalities, such as amides, ketones, esters, primary amines, aldehydes, carboxylic acids, and nitrogen-containing heterocycles. Therefore, the development of efficient methods for the synthesis of nitrile compounds has attracted much attention from synthetic chemists. Cyanomethylation of various substrates is a synthetically useful reaction because a variety of diversely cyano-containing compounds could be readily prepared. Acetonitrile is the simplest commercially available alkyl nitrile, which can act as the cyanomethyl carbanion source. The traditional method for the cyanomethylation of organic molecules is deprotonation of acetonitrile in the presence of strong base. Alternatively, transition-metal-catalyzed C—H bond activation of acetonitrile represents an attractive approach to cyanomethylated compounds due to its atom and step economy. In this communication, we developed a simple and highly efficient method for the synthesis of cyanated difluorostyrene derivatives by cyanomethylation of α-(trifluoromethyl)styrenes using cheap and commercially available acetonitrile as the CH2CN- source. The reaction proceeded smoothly in the presence of LiHMDS at room temperature and was finished within 1 h, affording the cyanated gem-difluoroalkenes in moderate to good yields. Furthermore, the cyanomethylation reaction exhibited good substrate scope and functional group compatibility. A general procedure for the cyanomethylation of α-(trifluoromethyl)styrenes with acetonitrile is as following: α-(trifluoromethyl)styrenes 1 (0.5 mmol) was dissolved in acetonitrile 2a (4 mL) at room temperature under argon atmosphere. Subsequently, a solution of the LiHMDS in THF (1.5 mL, 1.0 mol/L, 1.5 mmol, 3.0 equiv.) was added dropwise within 50 min and stirring was continued for further 10 min (monitored by TLC). After completion of the reaction, the reaction mixture was quenched with saturated aqueous solution of NH4Cl (15 mL) and extracted with ethyl acetate (5 mL×3). The combined organic layer was dried over anhydrous Na2SO4, filtered, and concentrated under vacuum. The crude residue was then purified by column chromatography on silica gel [(V(hexane)/V(ethyl acetate)＝10:1～6:1] directly to afford the pure target compounds.
Key words: α-(trifluoromethyl)styrenes, acetonitrile, cyanomethylation, cyanated difluorostyrenes
PDF全文下载地址:
点我下载PDF
