Reaction of 2-chloro-3-(1,3-dioxolan-2-yl)quinolines 1 with 1,2,4-triazole-5-thiol 2 leads to the formation of a mixture of 11-(2-hydroxyethyl)oxy-11H-[1,2,4]triazolo[5',1':2,3][1,3]thiazino[6,5-b]quinolines 3 and 11-(2-hydroxyethyl)oxy-11/-/-[1,2,4]triazolo[3',4':2,3][1,3]thiazino[6,5-£>]quinolines 4. The structures of the separated regioisomers were determined by homonuclear NOE difference spectroscopy and the results were further confirmed by desulfurisation.