Iron-Promoted Domino Annulation of α-Enolic Dithioesters with Ninhydrin under Solvent-Free Conditions: Chemoselective Direct Access to Indeno[1,2-<i>b</i>]thiophenes
An efficient, straightforward, and highly chemoselective strategy has been devised for the synthesis of a broad range of indeno[1,2-b]thiophenes through the annulation of α-enolic dithioesters with ninhydrin undersolvent-freeconditions. The advantages of this nucleophilic domino substitution/cyclization sequence are highlighted by the use of inexpensive and readily available FeCl3·6H2O as the catalyst