1, 8a-dihydro [l, 2, 4] triazolo [4, 3-a] pyridines 3, 1, 3-diaryl-3, 3a-dihy-dro [l, 2, 4] triazolo [4, 3-~] quinolines 4, and 1, 3-diaryl-l, lOb-dihy-dro [l, 2, 4] triazolo [3, 4-a] isoquinolines 5 has been developed. In a similar way, cycloadditions are carried out with C-ethoxycarbonyl-and C-acetyl-N-phenylnitrilimines. The ring cleavage of 3 in acidic medium yields the corresponding [(arylhydrazono) methyl] pyridinium chlorides 7. The conversion of the ...