Metal-free photoredox-catalysed formal C-H/C-H coupling of arenes enabled by interrupted Pummerer activation

Aryl-aryl cross-coupling constitutes one of the most widely used procedures for the synthesis of high-value materials that range from pharmaceuticals to organic electronics and conducting polymers. The assembly of (hetero)biaryl scaffolds generally requires multiple steps; coupling partners must be functionalized before the key bond-forming event is considered. The development of selective C-H arylation processes in arenes-which sidestep the need for prefunctionalized partners-is thus crucial for streamlining the construction of these key architectures. Here we report an expedient, one-pot assembly of (hetero)biaryl motifs using photocatalysis and two non-prefunctionalized arene partners. The approach is underpinned by the functionalization of a C-H bond in an arene coupling partner using the interrupted Pummerer reaction. A unique pairing of the organic photoredox catalyst and the intermediate dibenzothiophenium salts enables highly selective reduction in the presence of sensitive functionalities. The utility of the metal-free, one-pot strategy is exemplified by the synthesis of a bioactive natural product and the modification of complex molecules of societal importance.