The reaction of N-methyl-pdimethylaminothiobeneamide (3) with B number of a-halo ketones and one a-haloaldehyde gave stable Phydroxythiaaolinium salts (4) which could be subsequently dehydrated to the thiaaolium salts (5). When the intermediates were also substituted in the 5 position, both possible diastereoisomeric forms were detected by nmr spectroscopy. The effects of acidification and temperature variation on the nmr spectra ...