title: New facile tandem route to oxo- and thioxo[1,2,4]triazolo[1,5-a]pyridinium salts.
abstract: 2-Arylsulfanyl- and benzylsulfanylpyridinium N-arylimides (2), easily available from tetrazolo[1,5-b]pyridinium salts (1), participate in 1,3-dipolar cycloaddition with aryl isothiocyanates and aryl isocyanates to result in formation of fused thioxo- and oxo[1,2,4]triazolium salts (5 and 12), respectively. This transformation is interpreted as a regular 1,3-cycloaddition followed by spontaneous elimination of the aryl- or benzylsulfanyl group. Formation of these triazolium salts can be followed--under appropriate reaction conditions--by ring-opening reactions to afford some new triazolyldienes (6). Recognition of the intermediate participation of the thiolate anion along the pathway 1 --> 5 allowed elaboration of a simple procedure to 5 implying a tandem reaction sequence.
authors.affiliation: Chemical Research Center, Hungarian Academy of Sciences, H-1025 Budapest, Pusztaszeri út 59, Hungary.
authors.forename: Roberta
authors.initials: R
authors.lastname: Palkó
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Riedl
authors.forename: Orsolya
authors.initials: O
authors.lastname: Egyed
authors.forename: László
authors.initials: L
authors.lastname: Fábián
authors.forename: György
authors.initials: G
authors.lastname: Hajós