Reaction of trifluoromethylated ynamines with halogenating agents: a convenient access to 2-halo- and 2,2-dihalo-3,3,3-trifluoropropanamides

The reaction of trifluoromethylated ynamine with various halogenating agents was investigated. N,N-dialkyl(3,3,3-trifluoro-1-propynyl)amines (1) smoothly reacted with bromine to give, after treatment with sodium hydrogen carbonate, N,N-dialkyl-2-bromo-3,3,3-trifluoropropanamide (3-Br) in good yields. The reaction of 1 with an equimolecular amount of N-halosuccinimide (NXS) in acetonitrile–water (3/2 v/v) gave the corresponding 2-halo-3,3,3-trifluoropropanamides (3-X) in good to excellent yields. On the other hand, the treatment of 1 with NXS in anhydrous acetonitrile led to the formation of the addition products 7-X in high yields. Upon treating 7-X1 with an equimolecular amount of NX2S in aqueous acetonitrile, the corresponding 2,2-dihalo-3,3,3-trifluoropropanamides (8-X1X2) were produced in nearly quantitative yields.