Utilizing Nitroarenes and HCHO to Directly Construct Functional N‐Heterocycles by Supported Cobalt/Amino Acid Relay Catalysis

Due to the generation of multiple intermediates during the nitroarene reduction, precise interception of single one to develop tandem reactions involving both C−C and C−N bond formations still remains a significant challenge. Herein, the relay catalysis of a supported bifunctional cobalt catalyst with l‐proline has been successfully applied to establish a bran‐new reductive annulation reaction of nitroarenes and formaldehyde, which enables direct and diverse construction of both symmetrical and unsymmetrical 1,3‐diaryl imidazolines. It proceeds with operational simplicity, good substrate and functionality compatibility, and excellent step and atom‐efficiency. Mechanistic studies reveal that the Co‐catalyst exhibits a synergistic effect on the formation of key N‐hydroxy imine, and the l‐proline subsequently facilitates the key C−C bond formation. The current work opens a door to develop useful transformations with nitroarenes by reduction‐interrupted strategy. By relay catalysis of a supported bifunctional cobalt catalyst and L‐proline, a reductive annulation reaction of nitroarenes and formaldehyde involving both C−C and C−N bond formations is presented, which enables direct and diverse access to 1,3‐diaryl imidazolines.