Palladium/norbornene-catalyzed C–H/N–H cycloaddition of carbazoles with 2-halobenzoic acid derivatives

An example of palladium/norbornene-catalyzed C-H/N-H cycloaddition of carbazoles with 2-bromobenzoic acids is presented, in which a collection of important carbazoles is expeditiously obtained. Derivatives, including acyl halides, α-oxocarboxylic acids, anhydrides, and even amides, are all allowed. Preliminary mechanistic studies reveal that a rare six-membered spiropalladacycle is involved.