Brønsted Acid‐Catalyzed Regioselective (4+2) Cyclization of 2,3‐Indolyldimethanols With 3‐Vinylindoles for Synthesis of Bisindole‐Fused Six‐Membered Rings

A regioselective (4+2) cyclization of 2,3‐indolyldimethanols with 3‐vinylindoles was established under the catalysis of Brønsted acids, leading to the efficient construction of structurally diverse bisindole‐fused six‐membered rings in overall good yields (71%–95%) and with excellent regioselectivity. Moreover, a preliminary investigation on the asymmetric version of this reaction using chiral Brønsted acids was also conducted, demonstrating its potential for enantioselective synthesis of chiral bisindole‐fused six‐membered rings. This work not only offers a practical approach for synthesizing bisindole‐fused rings, but also gives a valuable example of highly regioselective cyclization involving 2,3‐indolyldimethanols, thereby significantly enriching the chemistry of 2,3‐indolyldimethanols.