Isolation and Reaction of New Aromatic Dications. 4-Thioniapyridinium Dications: 2-Aryl-(or 2-Alkyl-)4-methyl-3-oxo-2H-1,4-thiazin-2-ylium Tetrafluoroborates

Article abstract of DOI:10.1021/jo00245a016

2-Hydroxy-4-methyl-2-aryl(or -2-tert-butyl)-2H-1,4-thiazin-3-ones (5) generate carbocations 6 in trifluoroacetic acid solution at room temperature.These ions are sufficiently stable to be observed spectroscopically in this solution.Reaction of 6 with some nucleophiles are described.Stable crystalline tetrafluoroborates of 6 were isolated.From 1H NMR, 13C NMR, and UV-vis spectral data it was concluded that these cations are aromatic in nature and should be depicted as 9 and called 4-thioniapyridinium dications.