Synthesis of Cyclopenta[b]indoles via Rhodium-Catalyzed Cascade Migration-Annulation of 1-Sulfonyl-1,2,3-triazoles and Indoles.

A rhodium-catalyzed cascade 1,3-sulfinate migration, intermolecular [3+2] annulation of 1-sulfonyl-1,2,3-triazoles and indoles was achieved. The one-pot protocol provided a method to construct cyclopenta[b]indoles bearing four stereocenters in 45% to 99% yields with 1.6:1 to >20:1 diastereoselectivities. In addition, cyclopenta[b]indoles could be transformed into a variety of functionalized compounds, demonstrating the synthetic value of this migration-annulation strategy in ring system synthesis. [ABSTRACT FROM AUTHOR]