Brønsted Acid-Promoted Cyclodimerization of Indolyl Ketones: Construction of Indole Fused-Oxabicyclo[3.3.1]nonane and -Cyclooctatetraene Ring Systems.

A Brønsted acid-promoted cyclodimerization of C(3)-, C(2)-, or N(1)-substituted indole ketone derivatives is described. A wide range of structurally diverse bisindole fused-9-oxabicyclo[3.3.1]nonane and bisindole fused-cyclooctatetraene (COT) derivatives can be prepared in good to high yields with high efficiency.