Synthesis of Polysubstituted Cyclopentene and Cyclopenta[<i>b</i>]carbazole Analogues from Unsymmetrical 4‑Arylidene-3,6-diarylhex-2-en-5-ynal and Indole Derivatives via an Iodine Mediated Electrocyclization Reaction

An efficient method for the synthesis of polysubstituted cyclopentene and cyclopenta­[b]­carbazole derivatives through the iodine-promoted electrocyclization of substituted indoles and 4-arylidene-3,6-diarylhex-2-en-5-ynal derivatives is reported. Polysubstituted cyclopentene derivatives were produced through 4π electrocyclization reactions with indole, 7-methylindole, and 5-bromoindole as coupling partners, whereas cyclopenta­[b]­carbazole derivatives were produced via 6π electrocyclization in the case of methoxy (−OMe)-substituted indoles. The methods reported herein diastereo- and regioselectively proceed under straightforward and mild conditions.