碳-氟键断裂用于构建氟代异噁唑化合物  

Facile Synthesis of Fluorinated Isoxazoles via Consecutive Double C—F Bond Cleavage

作　　者：任智雯 任楠 张发光 马军安[1] Ren Zhiwen;Ren Nan;Zhang Faguang;Ma Junan(Department of Chemistry,Tianjin Key Laboratory of Molecular Optoelectronic Sciences,Tianjin Collaborative Innovation Center of Chemical Science & Engineering,Tianjin University,Tianjin 300072)

机构地区：[1]天津大学理学院化学系天津市分子光电科学重点实验室天津化学化工协同创新中心,天津300072

出　　处：《化学学报》2018年第12期940-944,共5页Acta Chimica Sinica

基　　金：国家自然科学基金(Nos.21472137;21532008;21772142);国家重点基础研究发展计划(973计划;No.2014CB745100)资助~~

摘　　要：含氟异噁唑骨架是许多药物及农药分子中的重要结构单元,其中单氟代异噁唑类化合物的合成方法还比较有限.从易得的α-三氟甲基-β-羰基酯出发,发展了基于碱促进的碳氟键断裂策略的氟代异噁唑化合物合成方法,该反应条件温和,操作简便,官能团兼容性良好,可以中等到较好的收率得到一系列3-氟代异噁唑化合物,且所得产物可进一步转化为生物活性分子的类似物.Fluorinated heterocycles represent a ubiquitous structural motif found in numerous pharmaceuticals, agrochemicals, and functional materials. This is especially true for fluorine-containing five-membered heteroaromatic compounds that have been widely investigated in various fields for a long time. In this context, fluorinated isoxazoles have emerged as valuable scaffolds owing to their diverse biological properties. Among various approaches that have been developed for the synthesis and functionalization of isoxazoles, efficient and modular route to fluorine-substituted isoxazoles are still limited. Traditional methods include the condensation of 2-fluoro-1,3-dicarbonyl derivatives with hydroxylamine, Au-catalyzed fluorocyclization of 2-alkyne O-methyloximes, and direct fluorination of isoxazoles. However, the wide applicability of these approaches often suffers from low chemical yields, harsh reaction conditions, and limited substrate scope. Herein, we describe a one-pot protocol for the construction of fluorinated isoxazoles from CF3-containing precursors with hydroxylammonium chloride. Typical features of this reaction include mild conditions, simple operations, and good functional group compatibility. This method provides facile access to a series of 3-F-5-aryl-isoxazoles in moderate to good yields from easily available α-CF3-β-keto esters. Moreover, further synthetic transformations of obtained isoxazoles to important bio-active molecular derivatives have also been demonstrated. A representative procedure for this reaction is as following: α-CF3-β-keto ester 1 (0.2 mmol, 1.0 equiv.), HONH2·HCl (46 mg, 0.66 mmol), pyridine (71 μL, 0.88 mmol), and CH3CN (3.0 mL) were added into an oven-dried vial equipped with a magnetic stir bar. The mixture was stirred at 75 ℃ for 12 h and monitored by thin-layer chromatography (TLC). After completion, 10 mL of water was added and the mixture was extracted with EtOAc for three times. The combined organic layers were washed with saturated NaCl and dried over Na2SO4. Th

关 键 词：碳-氟键断裂 异噁唑 一锅反应 含氟杂环 盐酸羟胺 

分 类 号：O626[理学—有机化学]