Aminothiazolium Hydroxide Inner Salts

Photolysis of 4-aminothiazolium salts in aqueous solution may cause ring opening, probably via a thiirane. to give a-cyano-jS-aminovinyl-disulfide or a-acylacetamidine derivatives (22). 

4-Mercapto- or 4-alkylidenethia2oIium hydroxide inner salts (1) (X = S or CRR ) have not been described. 

The reasonable stable products are characterized by an ir-absorption near 1615 cm . The 4-protons resonate near 6.2 ppm in the H NMR spectrum (23). NMR spectra exhibit a carbonyl atom signal near 173 ppm, whereas C-4 resonates near 8 108 these positions are characteristic of other mesoionic ring carbon atoms (24). In the mass spectra, decomposition with loss of CO, rupture of the 1,5 and 2.3 bonds with elimination of R NC2R 0 and cleavage of the 1,2 and 3,4 bonds with elimination of C2R 0S is observed (11) 

Acylisocyanates or isothiocyanates undergo cycloaddition with 5-hydroxy-THISs under so mild conditions that isolation of the initial adducts becomes possible (23). In cycloaddition reactions the 5-hydroxy-THISs can be replaced by their precursors (23). 

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Aminothiazolium hydroxide inner salts (2) (X = NR) are only known as N-phenyl (29) or acyl derivatives. (6. 34) or as hydrochlorides (35). 

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