Photochemistry frees arene functionalisation from metals

A new metal-free strategy offers a site-selective and general way to functionalise arenes. This photochemical method works on starting materials that feature many other functional groups, meaning it can be used for the late-stage modification of complex compounds like pharmaceuticals and agrochemicals.

Researchers from the University of Manchester, UK, developed a donor–acceptor complex that generates aryl radicals, enabling new substituents to subsequently be installed on the aromatic ring. Aryl radicals are highly unstable and so making them and controlling their reactivity has previously presented a huge challenge. Until now, synthetic chemists were limited to making radicals from aromatic compounds with electron withdrawing substituents.