Carbazole synthesis via an in situ trapping strategy with indolyl enol ethers

Abstract Indolyl enol ethers, generated from the alkoxy(indolyl)carbenium tetrafluoroborates 1 by treatment with sodium hydride, can be trapped with dimethyl acetylenedicarboxylate or N‐phenylmaleimide to furnish the selectively functionalized carbazoles 3,4,5,9,10 , and 13. In addition, the biaryl derivatives 6 and 11 are produced by a ring‐opening reaction of the primarily formed Diels‐Alder adduct. In the case of the biaryl derivative 6 , an X‐ray crystal structure analysis yields valuable information on constitutions and configurations in the biaryl series. The phenomenon of atropisomerism is discussed for this compound.