Synthesis of visible-light mediated tryptanthrin derivatives from isatin and isatoic anhydride under transition metal-free conditions

Abstract

Visible-light mediated synthesis of diverse tryptanthrin derivatives catalyzed by an organic dye has been achieved. An energy transfer reaction process leads to the self-condensation of isatin, as well as the cross-condensation of isatin and isatoic anhydride. The irradiation of the reaction mixture with a 23 W fluorescent bulb in the presence of Rose Bengal provides a transition metal-free, environmentally friendly and inexpensive alternative approach to synthesize this important heterocycle.