Iron-Ligand Coordination in Tandem Radical Cyclizations: Synthesis of Benzo[b]thiophenes by a One-pot Reaction of Iron 1,3-Diketone Complexes with 2-Thiosalicylic Acids

Iron—the mediator: 1,3‐Diketone ligands coordinated to iron undergo unprecedented tandem reactions with 2‐thiosalicylic acids to give 2‐substituted 3‐hydroxylbenzo[b]thiophenes in up to 98 % yield. A similar reaction with 2‐mercaptonicotinic acid gave a thieno[2,3‐b]pyridine derivative in 72 % yield (see scheme). A mechanism involving redox transformation and tandem radical cyclization of the coordinated ligands is proposed.