Synthesis and selected transformations of 3-oxido-1H-imidazole-4-carboxamides

Abstract

An efficient synthesis of newN-alkyl- andN-aryl-3-oxido-1H-imidazole-4-carboxamides based on exploration of inexpensive, commercially available ethyl acetoacetate, paraformaldehyde and primary amines is described. Representative compounds were tested in selected transformations, such as ‘sulfur-transfer reaction’ leading to imidazole-2-thiones and isomerization to corresponding imidazol-2-ones. Strong intramolecular hydrogen bonding via theN-oxide function results in the reduced reactivity of 3-oxido-1H-imidazole-4-carboxamides in both reactions. Moreover, the palladium catalyzed C(2)-arylation of imidazole ring as well as azide-alkyne [3+2] cycloaddition using theN-propargyl substituted 4-carboxamide derived from an imidazole 3-oxide as a dipolarophile, were also studied.