Synthesis and reactions of 1-azo-2-azonia-allene salts derived from pyridine derivatives

The 1-aza-2-azonia-allene salts prepared from 3-acetyl- or 3-benzoyl-pyridine via the corresponding hydrazone and alpha-chloroaryl-azo derivatives react with propionitrile to afford the corresponding 3-(3-pyridyl)-1,2,4-triazolium salts. The intramolecular cyclization products could be only isolated as the main products if the intermediate alpha-chlorophenyl-azo derivatives prepared from 4-benzoyl pyridine were treated with SbCl5 in presence or absence of propionitrile. Also, only 3-methyl-1,2,3-triazolo{[}1,5-a]pyridinium salts were obtained by reaction of the cumulene prepared from 2-acetyl-pyridine with or without propionitrile in good yields. Treatment of 3-pyridylindazolium hexachloroantimonates and 3-methyl-1,2,3-triazolo{[}1,5-a]pyridinium salts with Na2CO3 gave 3-pyridylindazoles and 3-methyl-1,2,3-triazolo{[}1,5-a]pyridine.