The syntheses and characterization of 4-substituted 4H-[1,2,4]triazol-1-ium phenylmethylides 8c−e and the new 5-aryl-1-phenacyl-1H-[1,2,4]triazolo[5,1-a]isoindole core 13 are reported for the first time. Treatment of triazolium salts 6c−e with triethylamine in the presence of picryl chloride resulted in a regioselective mixture of disubstituted ylides 7c−e and 8c−e. Intramolecular annulation of the latter in DMSO resulted in the formation of 1H-[1,2,4]triazolo[3,4-a]isoindole and 1H-[1,2,4]triazolo[5,1-a]isoindole derivatives, respectively . In order to explain this unusual chemical behavior, a theoretical approach, using AM1 and PM3 procedure methods, is also presented.