Addition of isocyanides to α-(methylthio)-benzylidenamidinium iodides: A surprising access to 2-(dialkylamino)imidazoles and 3,5-diamino-2H-pyrrolium salts

✍ Scribed by Georges Morel; Evelyne Marchand; Yvelise Malvaut

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 186 KB
• Volume: 11
• Category: Article
• ISSN: 1042-7163
• DOI: 10.1002/1098-1071(2000)11:5<370::aid-hc8>3.0.co;2-j

✦ Synopsis

A number of 2-(dialkylamino)-5-(methylthio)imidazoles 2 are obtained by treating the formamidinium iodides 1a,b with isocyanides R 3 NC under mild conditions. Reduction of these species can occur in the reaction medium to furnish the corresponding imidazoles 3. In some cases, double cycloaddition across the imine bond of starting salts 1 also provides the (azetidin-1-yl-methylene)ammonium iodides 4. Reactions with tert-butyl and isopropyl isocyanides in refluxing acetonitrile convert the acetamidinium iodide 1c into the 3,5-diamino-2Hpyrrolium salts 7. Mechanisms are suggested to account for these ring-closure processes.