Synthesis of <i>N</i> -Formyl Tetrahydroquinolines via Reductive <i>N</i> -Formylation of Quinolines with Formic Acid over Cobalt–Nitrogen Codoped Carbon Catalyst

N-Formyl tetrahydroquinolines are valuable N-containing chemicals with wide applications, and the reductive N-formylation of available quinolines with formic acid is a green route for their synthesis. However, this green synthesis route suffers from using noble metal catalysts. Herein, a non-noble cobalt- and nitrogen-codoped carbon (CoNC) catalyst was developed for the reductive N-formylation of quinolines with formic acid, and a series of N-formyl quinolines with different substituents were obtained in good to excellent yields. The CoNC catalyst can be reused 10 times without deactivation.