5-aminothiazolium salts as potential cyclic azomethine ylides: Base-induced cycloaddition reactions with aryl, alkyl, and benzoyl isothiocyanates

✍ Scribed by Adile Touimi Benjelloun; Georges Morel; Evelyne Marchand

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 220 KB
• Volume: 11
• Category: Article
• ISSN: 1042-7163
• DOI: 10.1002/(sici)1098-1071(2000)11:1<16::aid-hc4>3.0.co;2-f

✦ Synopsis

Reactions of the in situ generated thiazoles 2 with aryl and alkyl isothiocyanates appear to be totally regioselective and give the unexpected 5-(phenylthio)imidazolium-4-thiolates 3. Such rapid interconversion of mesoionic compounds is explained by a 1,3-dipolar addition to the C‫ס‬N bond of the heterocumulene followed by tBuNCS elimination. Similar interactions with benzoyl isothiocyanate exclusively proceed on the C‫ס‬S unsaturation of the heteroallene moiety and produce the 4-(phenylthio)thiazolium-5-amidines 12. Structural assignment of isolated imidazoles and thiazoles is based on 13 C NMR data and chemically confirmed by the NaBH 4 reduction of the alkylated derivatives 5 and 13. Efforts to isomerize the starting mesoionic thiazole 2a without the use of tBuNCS are unsuccessful.