Chemoselective N1 or C3 Cyclization Reaction of Indoles with Tetrasubstituted Olefins: Diastereoselective Synthesis of Pyrroloindoles or Cyclopenta[b]indoles Tethered with Seven-Membered Rings

An efficient chemoselective N1 or C3 cyclization reaction of indoles with tetrasubstituted olefins for the diastereoselective synthesis of pyrroloindoles or cyclopenta[b]indoles tethered with seven-membered rings is described. The N1 cyclization reaction was realized in the presence of t-BuOK to give pyrroloindoles in median to excellent yields, whereas the C3 cyclization products were obtained in median to high yields with I₂ and Al (OTf)₃.