Visible-light induced synthesis of 8H-indolo[3,2,1-de]phenanthridin-8-ones and related heterocycles using benzothiadiazole as photocatalyst

A simple and mild approach to access polycyclic 8H-indolo[3,2,1-de]phenanthridin-8-ones through a visible-light induced free radical cyclization of (2-bromophenyl)(9H-carbazol-9-yl)methanones using benzothiadiazole-containing photocatalyst is reported. This transition metal free method can be utilized for the synthesis of 7H-thieno[2',3':4,5]pyrido[3,2,1-jk]carbazol-7-one, 14H-isoquinolino[4,3,2-kl]phenoxazin-14-one, 14H-isoquinolino[4,3,2-kl]phenothiazin-14-one, and 10,11,12,13-tetrahydro-8H-indolo [3,2,1-de]phenanthridin-8-one. Moreover, some products were found to emit strong blue or green fluorescence. (C) 2022 Elsevier Ltd. All rights reserved.