Synthesis of Imidazo[4,5-c]pyrazoles via Copper-Catalyzed Amidine Cyclization

A new synthetic approach to 4-substituted imidazo­[4,5-c]­pyrazoles is proposed on the basis of the <i>N</i>′-(4-halopyrazol-5-yl)­amidine cyclization under the conditions of copper-catalyzed cross-coupling reactions. Using 5-aminopyrazoles and copper catalysts as starting materials, the method is inexpensive and convenient and allows a wide range of substituents at all positions of the imidazo­[4,5-c]­pyrazole nucleus.