The Ullmann coupling reaction catalyzed by a highly reactive rhodium-aryl complex derived from Grignard reagent and its application

A novel Rh-catalyzed one-pot Ullmann homo-coupling reaction of Grignard reagents was achieved. The reaction with bromobenzenes having an electron-donating group or halogen group gave the corresponding homo-coupling products in good yields, although heterocyclic or aliphatic bromides did not give the products. A highly reactive Rh(III)-bis(aryl) complex would play an important role in giving the homo-coupling products in this reaction. The reaction was applied to the integrin inhibitor that was being developed in parallel. As the result, we synthesized a novel inhibitor for integrins which is critical for several diseases.