Synthesis of 6-cyano and 6-unsubstituted 2-aryl-8-oxopurine from a common 2-oxoimidazole precursor

The benzyl urea of diaminomaleonitrile, prepared from commercially available starting materials, was reacted with aromatic aldehydes at room temperature. Intramolecular cyclization of the product, in basic solution, generated a substituted 2-oxoimidazole. This compound proved to be a common precursor for 2-aryl-6-cyano-8-oxopurines upon treatment with acid and for 2-aryl-6-unsubstituted-8-oxopurines, in the presence of base. A 1H NMR study of these simple and versatile reactions supports the mechanistic proposal.