Synthesis of Imidazolin-5-ones by Thermolysis of α-Azido Esters

Significance

Reported is the thermolysis of α-azido-α-aromatic esters to give 5-oxo-2,4-diphenyl-2,5-dihydro-1H-imidazol-2-carboxylates. The starting azides are obtained from the relevant bromides and can be isolated by forming them at lower temperatures or thermolyzed in situ to form the cyclized products. Only α-aromatic esters were successful in this reaction, probably due to the right balance of α-proton acidity, and intermediate imine nucleophilicity. Whilst it is a little surprising that this reaction has not been previously studied, this deficiency could be partially ­explained by the fact that it only takes place in ­polar aprotic solvents, such as DMF or DMSO.