Small organic molecules work as catalysts in chemical reactions. Recent synthesis strategies have employed the synergistic activity of different catalysts to activate reaction components and facilitate the formation of new bonds. In many cases, this enables a transformation that would otherwise be impossible in the presence of a single catalyst. Ideally, chemists would like to functionalise bonds between carbon and hydrogen to build up molecular complexity from simple and otherwise inert building blocks. Based on this concept, the EU-funded SYNCAT (Development of a synergistic catalysis protocol for the enantioselective functionalisation of aldehydes) project set out to investigate the development of a broadly applicable synthetic methodology enabling access to privileged structural motifs. In this context, scientists combined photoredox catalysis and organocatalysis to develop a method for the direct arylation of allylic carbon-hydrogen bonds. The transformation tolerated the addition of a wide range of functional groups and could be applied to complex substrates. To expand the applications of the carbon-hydrogen functionalisation reaction, they combined it with a transition metal catalyst. The palladium-mediated catalysis generated a variety of substrates that would normally be considered benign under traditional reaction conditions. Overall, the use of photoredox catalysis to enable previously challenging transformations has exciting implications for the synthesis of a range of pharmaceutically relevant molecules. Furthermore, this new method should provide a broad base for developing novel transformations in the field of synthetic chemistry.
Catalyst, chemical reaction, SYNCAT, carbon-hydrogen bond