Pd/C-Catalyzed Reductive Formylation of Indoles and Quinolines Using Formic Acid

A two-step, one-pot domino reaction methodology was developed to synthesize a variety of N-formylindolines and N-formyltetrahydroquinolines from the corresponding indoles and quinolines. In the first step, the heterocyclic compounds are reduced to the corresponding dihydro or tetrahydro products by a Pd/C-catalyzed transfer hydrogenation using formic acid as a hydrogen donor. In the second step, nitrogen is formylated by formic acid to afford the final products in very good isolated yields.