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.