Organocatalytic, rapid and facile cyclotrimerization of isocyanates using tetrabutylammonium phthalimide-N-oxyl and tetraethylammonium 2-(carbamoyl)benzoate under solvent-free conditions

Tetrabutylammonium phthalimide-N-oxyl and tetraethylammonium 2-(carbamoyl)benzoate were found to be effective and easily accessible organocatalysts for selective cylotrimerization of aryl and alkyl isocyanates under mild reaction conditions. The reaction proceeds smoothly using very low catalyst loadings of these metal-free organocatalysts (0.025 and 0.25 mol%, respectively) under solvent-free conditions at room temperature within a very short reaction time.

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► Cyclotrimerization of isocyanates is a very important reaction in manufacturing of coating materials such as polyurethanes.
► Organocatalytic protocols demonstrate considerable advantages over traditional catalytic systems.
► Cylotrimerization of isocyanates is catalyzed by tetrabutylammonium phthalimide-N-oxyl (1) and tetraethylammonium 2-(carbamoyl)benzoate (2) as efficient organocatalysts.
► High to quantitative yields of the products were obtained under mild reaction conditions.