Heterogeneous synthesis of benzo[f]indole-4,9-diones derivatives using sulfonic resin and photocatalytic study

This research introduces a heterogeneous approach utilizing a resin-bound sulfonic acid catalyst (Dowex®-H) to synthesize benzo[f]indole-4,9-dione derivatives using β-enaminones systems and 2-bromonaphtoquinone. This method facilitates synthesizing a diverse range of compounds with varying substitution patterns, achieving yields of 88 %. The catalyst can be reused for up to five cycles without requiring reactivation. These compounds absorption spectra also show absorption (λ_max) around 250–260 nm with a significant transition around 400 nm. Their photocatalytic potential was assessed by the model reaction of benzylamine photooxidation, achieving a yield of over 99 % within 36 h.