Research Article

Organic semiconductor photocatalyst can bifunctionalize arenes and heteroarenes

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Science  26 Jul 2019:
Vol. 365, Issue 6451, pp. 360-366
DOI: 10.1126/science.aaw3254

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Two-for-one approach to photoredox

In photoredox catalysis, an excited chromophore typically activates a single reactant either by oxidizing or reducing it. Ghosh et al. used a semiconductor catalyst to activate two reactants at once by quenching both an excited electron and the residual positive hole (see the Perspective by Swift). As such, two different reactive carbon or halide fragments could be appended to separate sites on an aryl ring. The catalyst also tolerated strong nucleophiles such as cyanide and could be recovered easily and reused.

Science, this issue p. 360; see also p. 320


Photoexcited electron-hole pairs on a semiconductor surface can engage in redox reactions with two different substrates. Similar to conventional electrosynthesis, the primary redox intermediates afford only separate oxidized and reduced products or, more rarely, combine to one addition product. Here, we report that a stable organic semiconductor material, mesoporous graphitic carbon nitride (mpg-CN), can act as a visible-light photoredox catalyst to orchestrate oxidative and reductive interfacial electron transfers to two different substrates in a two- or three-component system for direct twofold carbon–hydrogen functionalization of arenes and heteroarenes. The mpg-CN catalyst tolerates reactive radicals and strong nucleophiles, is straightforwardly recoverable by simple centrifugation of reaction mixtures, and is reusable for at least four catalytic transformations with conserved activity.

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