One-Pot C–H Formylation Enabled by Relay Catalysis of Manganese(I) and Iron(III)

A practical one-pot C–H formylation approach enabled by the relay catalysis of manganese(I) and iron(III) has been developed. The effect of the directing group exhibited that 2-pyrimidinyl was a suitable directing group to promote the C–H hydroxymethylation and was also compatible in the subsequent aerobic oxidation. This formylation reaction, in which water is the only byproduct, showed high selectivity and efficiency across a broad substrate scope. The use of non-noble transition metals to promote relay catalysis provides a practical and scalable approach to C–H formylation. The loading of the manganese(I) catalyst could be decreased to as low as 0.5 mol % on a 5 g scale reaction.