Re-investigation of the Coupling Reaction of 2-Aryl-1,1-dibromo-3,3,3-trifluoropropenes. Preparation of Perfluoroalkylated [3]Cumulenes
作者:Hidemitsu Uno、Nobumasa Nibu、Noboru Misobe
DOI:10.1246/bcsj.72.1365
日期:1999.6
The coupling reaction of perfluoroalkylated 2-aryl-1,1-dibromoalkenes using zinc and copper(I) bromide gave stereoisomeric mixtures of [3]cumulenes and [4]radialenes. The ratio of [3]cumulenes and [4]radialenes mainly depended upon the reaction temperature and the electronic character of the aryl group. When the coupling reaction was carried out at −40 °C, (E)- and (Z)-[3]cumulenes were obtained in good selectivity and only trace amounts of [4]radialenes were detected by a 19F NMR analysis. On the other hand, a similar reaction at −60 °C afforded a considerable amount of [4]radialene isomers. When the cis-[3]cumulenes were heated at an appropriate temperature, selective isomerization to trans-[3]cumulenes occurred.
使用锌和溴化铜(I)进行全氟烷基化的2-芳基-1,1-二溴烯偶联反应生成了[3]累烯和[4]放射烯的立体异构混合物。[3]累烯和[4]放射烯的比例主要依赖于反应温度和芳基的电子特性。当在-40 °C进行偶联反应时,获得了良好选择性的(E)-和(Z)-[3]累烯,仅在氟-19核磁共振分析中检测到微量的[4]放射烯。另一方面,在-60 °C进行类似反应时,产生了相当数量的[4]放射烯异构体。当顺式-[3]累烯在适当温度下加热时,会发生选择性异构化转化为反式-[3]累烯。