Synthesis of Thiophenes from Pyridines Using Elemental Sulfur

Abstract

Abstract We describe a skeletal editing of pyridines to afford thiophenes through a formal [4 + 1] reaction using elemental sulfur. 2‐Arylpyridines are converted to ring‐opened aza‐triene Zincke ketone structures, followed by simple treatment with sulfur to give 2‐aroylthiophene products directly. The amphiphilic character of octasulfur enables smooth reaction with the Zincke dienamine, affording the cyclized products under mild and neutral conditions. We illustrate this new disconnection with a synthesis of the anti‐inflammatory drug suprofen from a pyridine starting material.