Photochemical Synthesis of Carbazoles Using an [Fe(phen)3](NTf2)2/O2 Catalyst System: Catalysis toward Sustainability.

An increasingly sustainable photochemical synthesis of carbazoles was developed using a catalytic system of Fe(phen)3(NTf2)2/O2 under continuous flow conditions and was demonstrated on gram-scale using a numbering-up strategy. Photocyclization of triaryl and diarylamines into the corresponding carbazoles occurs in general in higher yields than with previously developed photocatalysts.