Urea derivatives from carbon dioxide and amines by guanidine catalysis: Easy access to imidazolidin-2-ones under solvent-free conditions

A novel methodology to easily access imidazolidin-2-ones from propargylamines, primary amine and CO2 with TBD (1,5,7-triazabicyclo[4.4.0] dec-5-ene) or MTBD (7-methyl-1,5,7-triazabicyclo[4.4.0] dec-5-ene) as catalysts under solvent-free conditions is here reported. Bicyclic guanidines, able to catalyze the formation of oxazolidinones from secondary propargylamines and CO2, are now presented for the first time as effective organocatalysts for the chemical fixation of CO2 into linear and cyclic ureas. Plausible reaction pathways are proposed on the basis of experimental findings.