Copper-Catalyzed Synthesis of 3-Aryl-9H-imidazo[1,5-a]indol-9-ones Using Oxygen as the Sole Oxidant

A three-component strategy was developed for 3-phenyl-9H-imidazo-[1,5-a]-indol-9-one preparationfrom indole-2-carboxaldehydes, aromatic aldehydes, and ammonium acetateunder copper catalysis conditions. In this process, a new five-memberedring was formed and the C3 position in the indole substrate was selectivelyoxidized into a ketone skeleton using oxygen as the sole oxidant andammonium acetate as the nitrogen source. Furthermore, same productsalso could be achieved from indole-2-carboxaldehydes and benzyl aminesunder similar reaction conditions.

Automated summary

A three-component strategy using indole-2-carboxaldehydes, aromatic aldehydes, and ammonium acetate as starting materials was developed for the preparation of 3-phenyl-9H-imidazo-[1,5-a]-indol-9-one under copper catalysis conditions. This strategy involved the selective oxidation of the C3 position in the indole substrate into a ketone skeleton using oxygen as the sole oxidant and ammonium acetate as the nitrogen source, resulting in the formation of a new five-membered ring. Similar reaction conditions also allowed the synthesis of the same products from indole-2-carboxaldehydes and benzyl amines.