SYNTHESIS OF 1,2,4-TRIAZOLIUM SALTS - REACTION OF 1-AZO-2-AZONIA-ALLENE SALTS WITH NITRILES

Alkyl ketone hydrazones 1 are oxidized with tert-butylhypochlorite to give geminal chloro azo compounds 2. These react with SbCl5, to give 1-aza-2-azonia-allene salts 3 as reactive intermediates which are intercepted with nitriles to yield 3H-1,2,4-triazolium salts 5. In most cases these salts rearrange spontaneously to form 1H-triazolium salts 6. Hydrolysis of 6e-g by NaOH provide bases 7a-c, which react with picric acid to give 1H-pyrazolium picrates 8.