Re-investigation of the coupling reaction of 2-aryl-1,1-dibromo-3,3,3- trifluoropropenes. Preparation of perfluoroalkylated [3]cumulenes

Article abstract of DOI:10.1246/bcsj.72.1365

The coupling reaction of perfluoroalkylated 2-aryl-1,1-dibromoalkenes using zinc and copper(1) 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 ¹⁹FNMR 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.