One‐Pot Reactions of Ynones with Isothiocyanates for Accessing 2‐Aminothiophenone and Indole‐Fused/Indole‐Substituted Thiophenone Derivatives

Abstract A copper or silver‐catalyzed cascade addition/5‐ exo‐dig cyclization/isomerization reaction of isothiocyanate with ynone has been developed. This strategy enables the synthesis of a variety of ( Z )‐2‐ylidene‐5‐aminothiophen‐3‐one derivatives with diverse substitutions in a single vessel. The method is featured with pot‐economy as well as regio‐ and Z ‐selectivity. Several biologically active molecules could be modified using this strategy. Moreover, the relevant indole‐fused and indole‐substituted thiophenone derivatives were also assembled in one pot by merging this strategy with other bond formation methods. Based on the experiments and the related reports, a cascade pathway triggered by the addition of ynone‐derived radical towards the C( sp )‐atom of isothiocyanate was proposed to elucidate the probable process of the transformation.