Thermal rearrangement of 3‐ and 2‐(propargylthio)thiophene: Formation of the thiopyrans 5<i>H</i>‐thieno[3,2‐b]thiin and 6<i>H</i>‐thieno[2,3‐b]thiin

Abstract

Abstract 5 H ‐Thieno[3,2‐b]thiin (III) and 6 H ‐thieno[2,3‐b]thiin (VI) are formed in excellent yields by heating solutions of 3‐ and 2‐(propargylthio)thiophene (I) and (IV), respectively, in hexamethylphosphoric triamide at 170–180°.