Fluorinated acetylenes. Part IV. Preparation of NN-bistrifluoromethylprop-1-ynylamine and the attempted preparation of fluoro-NN-bistrifluoromethylethynylamine

Abstract

N-Bromobistrifluoromethylamine reacts with propyne under free-radical conditions to give a high yield of a mixture of cis- and trans-bromo-NN-bistrifluoromethylprop-1-enylamine. Dehydrobromination of the cis–trans olefin mixture gives mainly NN-bistrifluoromethylpropadienylamine and NN-bistrifluoromethylprop-1-ynylamine, together with a small amount of NN-bistrifluoromethylprop-2-ynylamine. The reaction of hydrogen bromide with NN-bistrifluoromethylprop-1-ynylamine under ionic conditions yields 1-bromo-NN-bistrifluoromethylprop-1-enylamine, which indicates that the acetylene is polarised in the sense (CF₃)₂N·[graphic omitted]·CH₃. The reaction of N-bromobistrifluoromethylamine with vinyl fluoride under free-radical conditions gives a mixture of 2-bromo-2-fluoro-NN-bistrifluoromethylethylamine and 2-bromo-1-fluoro-NN-bistrifluoromethylethylamine (ratio 94:6); a corresponding reaction under ionic conditions yields mainly 2-bromo-1,1-difluoroethane and perfluoro-2-azapropene. 2-Bromo-2-fluoro-NN-bistrifluoromethylethylamine is dehydrobrominated readily to give a mixture of cis- and trans-2-fluoro-NN-bistrifluoromethylvinylamine and these olefins when treated separately with bromine in the presence of aluminium bromide yield threo- and erythro-1,2-dibromo-NN-bistrifluoromethylethylamine, respectively. Dehydrobromination of a mixture of the 1,2-dibromo-isomers gives mainly cis-and trans-1-bromo-2-fluoro-NN-bistrifluoromethylethynylamine, together with small amounts of NN-bistrifluoromethylethynylamine and bromo-NN-bistrifluoromethylethynylamine. A reactive compound is also formed in low yield and this forms a yellow oil on distillation; this reactive compound may be fluoro-NN-bistrifluoromethylethynylamine.