E- or Z-Selective synthesis of 4-fluorovinyl-1,2,3-triazoles with fluorinated second-generation Julia–Kocienski reagents
作者:Rakesh Kumar、Govindra Singh、Louis J. Todaro、Lijia Yang、Barbara Zajc
DOI:10.1039/c4ob02179g
日期:——
α-fluoropropargyl benzothiazole sulfone with aryl, alkyl, and metallocenyl azides furnished second-generation Julia–Kocienski reagents in good to excellent yields. Condensation reactions of these reagents with aldehydes can be tuned to yield E or Z-alkenes selectively. Under mild conditions with DBU as the base, reactions of aldehydes furnished E-alkenes as the major isomer. On the other hand, in condensation reactions
描述了N-取代的4-(1-氟乙烯基)三唑的高度模块化的方法。TMS保护的α-氟炔丙基苯并噻唑砜与芳基,烷基和茂金属叠氮化物的原位去甲硅烷基化和Cu催化的连接反应为第二代Julia-Kocienski试剂提供了良好的收率。可以调节这些试剂与醛的缩合反应,以选择性地产生E或Z-烯烃。在以DBU为碱的温和条件下,醛的反应得到E-烯烃为主要异构体。另一方面,在以LHMDS为碱的缩合反应中和在适当的溶剂中,醛和酮都反应生成具有Z-选择性的氟代烯烃。通过X射线晶体学分析和NMR数据比较,对在酮与两种Julia试剂的反应中获得的E / Z烯烃进行立体化学分配。该方法允许双键处的N 1-取代基和取代基有效且容易地多样化。