An efficient synthesis of 3-trifluoromethylated 1,2,4-triazolium salts

Hydrazones of trifluoromethyl ketones I are converted with tert-butyl hypoc hlorite to 1-chloro-1-(trifluoromethyl)azo compounds 2, which at -10 degree s C react with antimony pentachloride to produce the trifluoromethylated 1- aza-2-azoniaallene salts 3 as reactive intermediates. The cations 3 are app lied as synthetic blocks for the preparation of the 3-trifluoromethylated 1 ,2,4-triazolium heterocycles 5a-k. An X-ray structural analysis was carried out for 5f and the results compete well with the data obtained by AM1 calc ulation.