A toolbox approach to revealing a series of naphthocarbazoles to showcase photocatalytic reductive syntheses

Abstract

The development of highly reducing photocatalysts to functionalize arenes via the generation of reactive aryl radicals under mild and environmentally benign reaction conditions has emerged as a noteworthy approach in the realm of organic synthesis. Herein, we report a readily synthesized series of novel naphthocarbazole derivatives (NCs) as organo-photocatalysts, which, upon irradiation under 390 nm light, acquire high reducing power to catalyze several reductive transformations. The promising properties revealed by in depth photophysical and electrochemical studies ( = −1.9 V to −2.07 V vs. SCE, τ = 5.59 to 7.12 ns) demonstrate NCs to be versatile catalysts, and notably, rational variation of the substituents (NC1–NC6) modulates their success as efficient photoreductants. Detailed DFT calculations of the frontier MO diagrams and energy levels revealed them to be non-donor–acceptor type molecular scaffolds. The applicability of the NCs as catalysts was demonstrated in reductive dehalogenative borylation, phosphorylation, and dehydrohalide intramolecular C–C coupling reactions, as well as the dimerization of carbonyls and imines. Visible-light-irradiated selective reductive desulfonylation from heteroaromatics and peptides further enhances their synthetic utility.