Synthesis of Dibenzo[<i>a</i>,<i>c</i>]phenazines through Brønsted Acid-Catalyzed Skeletal Editing of 2-Arylindoles with 1,2-Diaminoarenes

Herein, Brønsted acid-catalyzed skeletal editing of 2-arylindoles with 1,2-diaminoarenes in the presence of tert -butyl nitrite (TBN) has been developed to prepare various dibenzo[ a, c ]phenazines in moderate to good yields. Mechanistic studies revealed that this skeletal editing of indoles involved a sequence of nitrosation, condensation, cyclization, diazotization, and intramolecular electrophilic substitution over five steps in one pot. More importantly, the dibenzo[ a, c ]phenazine could be easily obtained on a gram scale and novel π-extended polyaromatic dibenzo[ a, c ]phenazine derivatives were obtained by further transformations that show the fluorescence emission wavelength in near-infrared region I (NIR-I). This example represents the first skeletal editing of indoles through a ring-opening and denitrogenation strategy.