Synthesis of Imidazolidinone, Imidazolone, and Benzimidazolone Derivatives through Oxidation Using Copper and Air

A new synthetic method of urea derivatives using copper and air was developed. These mild conditions provided moderate to very good yields for 15 examples (53-93%), while low yields were obtained with sterically hindered substrates (3 examples). The reaction was found to go through an in situ generated copper- N-heterocyclic carbene, which was then oxidized into cyclic urea derivatives possessing alkyl, benzyl, aryl, hydroxy, Boc-protected, and tertiary amine groups.