Catalytic multicomponent reaction involving a ketyl-type radical

The development of new strategies and concepts towards the synthetic utilization of carbonyl compounds is of pivotal relevance. Nevertheless, the generation of ketyl radicals requires relatively harsh conditions and a large excess of reductants, which represents a long-standing, unsolved problem that hampers the broad application of ketyl coupling processes. Several catalytic approaches have been developed to generate ketyl radicals and successfully applied in reductive cyclizations and two-component cross-coupling reactions. However, catalytic multicomponent reactions that involve a ketyl radical remain rare, but are in high demand owing to their ability to rapidly generate complexity in molecules. Here we report a multicomponent, redox-neutral photocatalytic manifold that combines readily available aldehydes, feedstock 1,3-butadiene and various nucleophiles to build architecturally complex and functionally diverse homoallylic alcohols in one pot. This operationally straightforward method exhibits a wide functional group tolerance, enables the synthesis of drug-like architectures that are not readily accessible by other methods and is applied towards key intermediates of several natural products, which makes the strategy of broad interest in areas such as synthetic and medicinal chemistry. Ketyl radicals can be used in a range of reactions, but their generation often requires harsh conditions and a large excess of reductants. Now, a multicomponent, palladium-photocatalysed reaction between aldehydes, 1,3-butadiene and N, S, O and C nucleophiles to build architecturally complex homoallylic alcohols is reported wherein ketyl-type radicals are generated under mild conditions.