Synthesis of the Carbazole Scaffold Directly from 2-Aminobiphenyl by Means of Tandem C-H Activation and C-N Bond Formation

An efficient method for the synthesis of the carbazole scaffold was designed and investigated. The method was developed to produce substituted carbazoles by an intramolecular combination of a free amine group and an arene. The steps of the method involved tandem Pd-catalyzed C–H activation and intramolecular C–N bond formation. The method showed good functional group tolerance, and substituent(s) could be on either of the two rings or on both of the two rings of the 2-aminobiphenyl substrate. After ring closure, the reduced Pd catalyst was oxidized to PdII by hydrogen peroxide. The novel method was also demonstrated to operate excellently with the corresponding 2-N-acetylaminobiphenyls.