A catalyst-free bis(triflyl)ethylation/benzannulation reaction: rapid access to carbazole-based superacidic carbon acids from alkynols.

Carbazoles possessing Tf2CHCH2 groups were obtained by the reaction of 1-(indol-2-yl)but-3-yn-1-ols with in situ-generated Tf2C＝CH2 through vicinal difunctionalisation of the alkyne moiety, where the vinyl-type carbocation intermediate was selectively attacked by the indole moiety and not by the carbanion moiety. [ABSTRACT FROM AUTHOR]