Polyfluoroalkyl derivatives of nitrogen. Part XLIII. Reactions of N-bromobis(trifluoromethyl)amine with 1-fluoropropene under free-radical and under ionic conditions

Abstract

Photochemical reaction of N-bromobis(trifluoromethyl)amine with 1-fluoropropene in the vapour phase gives a mixture of the 1 : 1 adducts 2-bromo-1-fluoro-NN-bis(trifluoromethyl)propylamine and 2-bromo-2-fluoro-1-methyl-NN-bis(trifluoromethyl)ethylamine in the ratio 46 : 54. Under conditions conducive to the formation of ionic intermediates (–78 °C in the dark in the liquid phase), stereospecific anti-addition to the olefin takes place and the 1 : 1 adducts are formed in the ratio 90 : 10 (cis-isomer) and 77 : 23 (trans-isomer). All the adducts undergo dehydrobromination by anti-elimination to give the corresponding (E)- or (Z)-olefins, except for (1R,2S)-2-bromo-1-fluoro-NN-bis(trifluoromethyl)propylamine, which undergoes mainly syn-elimination to afford a mixture of (E)- and (Z)-1-fluoro-NN-bis(trifluoromethyl)prop-1-enylamine in the ratio 82 : 18.