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.