Polyfluoroalkyl derivatives of nitrogen. Part XXXIX. Preparation of NN-bistrifluoromethylamino-substituted allenes

Abstract

N-Bromobistrifluoromethylamine reacts with an excess of allene in the vapour phase in light to give the 1 : 1 adducts 2-bromo-NN-bistrifluoromethylprop-2-enylamine and 2-(bistrifluoromethylamino)-3-bromopropene in the ratio 90 : 10; the 2 : 1 adduct 1,3-di-(NN-bistrifluoromethylamino)-2,2-dibromopropane is obtained from a 2 : 1 molar mixture of the N-bromo-amine and allene. The major 1 : 1 adduct and the 2 : 1 adduct are dehydrobrominated in high yield to give the allenes NN-bistrifluoromethylpropadienylamine and 1,3-di(bistrifluoromethylamino)propadi-ene. respectively. In the liquid phase in the dark the N-bromo-amine reacts with the monosubstituted allene to yield a mixture of 3,3-di(bistrifluoromethylamino)-2-bromopropene and cis- and trans-1,3-di(bistrifluoromethylamino)-2-bromopropene; the former adduct gives 1,1 -di(bistrifluoromethylamino)propadiene on dehydrobromination. 1,3,3-Tri(bistrifluoromethylamino)propadiene is formed by dehydrobromination of the NN-bromo-amine adduct with the 1,3-disubstituted allene; it reacts with the N-bromo-amine to afford NN-bistrifluoromethylamine and 1,1,3-tri(bistrifluoromethylamino)-3-bromopropadiene.