Abstract The Au(III)-mediated oxidative cyclization of a series of 2-hydrazinylquinolines is reported. This intramolecular reaction represents a reliable way towards obtaining various 3H-1,2,4-triazolo[4,3-a]quinolin-10-ium cations. The molecular structures of three of the starting compounds (2-(1-methyl-2-(pyridin-2-ylmethylene)hydrazinyl)quinoline, 2-(1-methyl-2-(thiophen-2-ylmethylene)hydrazinyl)quinoline, 2-((2-methyl-2-(quinolin-2-yl)hydrazono)methyl)aniline) as well as of one cyclized system (3-methyl-1-(pyridin-2-yl)-3H-1,2,4-triazolo[4,3-a]quinolin-10-ium dichloridoaurate(I)) were determined by means of single-crystal X-ray diffraction.