Pyrene-4,5-dione as a Visible-Light Organic Photocatalyst for Photooxidation, Photoredox, Energy Transfer, and HAT Reactions

Pyrene-4,5-dione (PQ) is demonstrated to be a metal-free, visible-light organic photocatalyst capable of meditating four major photochemical activation modes: photooxidation, energy transfer, photoredox, and hydrogen atom transfer (HAT). Under mild conditions using blue LEDs, PQ enables diverse synthetic transformations including singlet oxygen oxidations, [2+2] cycloadditions, C–H fluorination, reductive C–C bond formation, oxidative hydroxylation of boronic acids and HAT-driven alkylation. Its performance is comparable to benchmark systems, whilst offering the advantages of visible light absorption and a greener profile compared to typical metal complexes photocatalysts. PQ is readily recovered by chromatography and reused without loss of catalytic activity or structural integrity. This work highlights the potential of PQ as a practical and versatile photocatalyst for visible-light-driven organic synthesis.