DBU-Mediated [3+3] Annulation of Indolin-3/2-ones and Ethenesulfonyl Fluorides: An Approach to Indole-Fused δ-Sultones

A general and efficient approach to the synthesis of various indole-fused δ-sultones has been developed via DBU-mediated [3+3] cyclizations of indolin-3/2-ones and β-(hetero)arylethenesulfonyl fluorides. Notably, the reaction shows a broad substrate scope, and over 70 examples were exhibited in up to 99% isolated yield. In addition, some of the synthesized compounds showed significant antitumor activity against HepG2 and Caco-2 cells in vitro, which might provide promising insights for the future discovery and rational design of novel antitumor agents.