Polyfluoroalkyl derivatives of nitrogen. Part 44. The reactions of N-bromobis(trifluoromethyl)amine with open-chain 1,3-dienes and cyclohexene under ionic conditions

Abstract

The reactions of N-bromobis(trifluoromethyl)amine with buta-1,3-diene, 2-methylbuta-1,3-diene, and 2,3-dimethylbuta-1,3-diene give relatively high yields of mixtures of the 1,2- and 1,4-adducts (CF₃)₂NCR¹(CH₂Br)CR₂CH₂ and CH₂BrCR¹CR²CH₂N(CF₃)₂ in the ratios 75 : 25 (R¹= R²= H), 47 : 53 (R¹= Me, R²= H), and 11 : 89 (R¹= R²= Me); the buta-1,3-diene reaction carried out in diethyl ether and methylene chloride gives the adducts in the ratio 16 : 84 and 59 : 41, respectively. With 2-methylbuta-1,3-diene the adducts (CF₃)₂NCH(CH₂Br)CMeCH₂ and CH₂BrCHCMeCH₂N(CF₃)₂ are also formed (8%) in the ratio 44 : 56. The buts-1,3-diene 1,2- and 1,4-adducts dehydrobrominate readily (KOH) to afford 2- and 1-bis(trifluoromethyl)aminobuta-1,3-diene, respectively. The 1,2-adduct is stable at 220 °C, but the 1,4-adduct at this temperature slowly forms a mixture of rearranged products; on prolonged heating the major product is 3-bromobis(trifluoromethyl)but-1-enylamine. Addition of the N-bromoamine to cyclohexene at low temperature in the dark gives the trans-diequatorial adduct (86%) which is resistant to dehydrobromination under a variety of conditions.