Cobalt-salen complexes/organic photoredox-cocatalyzed selective oxidative formylation of enaminones

A selective oxidation of enaminones to achieve formylation <i>via</i> cobalt-salen/photoredox-cocatalyzed synergy was developed, providing the corresponding formylation products in good yields under mild conditions. This photochemical synthetic strategy does not need to use peroxide as an oxidant, and hence is compatible with a wider range of oxidation-sensitive-group-containing substrates. Investigations indicated that the selective oxidation of the <i>N</i>-methyl group in enaminones by the [Co^III]-containing complex plays a vital role.