4‐(2‐Hydroxyphenyl)imidazolium Salts as Organocatalysts for Cycloaddition of Isocyanates and Epoxides to Yield Oxazolidin‐2‐ones

Abstract

AbstractNovel salts based on 1,3‐dibutyl‐4‐(2‐hydroxyphenyl)‐1H‐imidazolium bromide or iodide have been developed as bifunctional organocatalysts for the cycloaddition reaction of epoxides and isocyanates to form 3,4‐ and 3,5‐disubstituted oxazolidin‐2‐ones. The molecular structure of these compounds was determined spectroscopically and confirmed by X‐ray diffraction analysis. Imidazolium compounds were screened as catalysts to produce a range of oxazolidinones. The influence of the substituents on the aromatic ring and the counterion of the catalysts on the catalytic activity have been studied, showing that 1,3‐dibutyl‐4‐(5‐fluro‐2‐hydroxyphenyl)‐1H‐imidazolium iodide (4 d) was the most active catalyst for this process in the absence of a cocatalyst.