Light-Mediated Photoredox/Cobalt Dual Catalysis for Multisubstituted Enal Synthesis from Alkyne Feedstock

α,β-Unsaturated aldehydes are important structural motifs in organic synthesis and have wide applications in the synthesis of olfactory compounds, agrochemicals, and drugs. While the traditional synthesis of α,β-unsaturated aldehydes requires harsh reaction conditions involving multistep processes, we have developed a unique one-step synthesis utilizing an ene–yne coupling reaction, an efficient process to build the linear carbon chain in an atom-economic way. The traditional reductive ene–yne coupling reaction requires (super)stoichiometric metal, Grignard reagent, borane, or silane as a reductant. The present method describes an alternative route using Hantzsch ester as an organic reductant under Co–Ir dual catalysis. Importantly, the specific choice of the alkene, i.e., vinylene carbonate, was key to obtaining the α,β-unsaturated aldehydes following a reaction sequence of reductive ene–yne coupling, β-oxygen elimination, decarboxylation, and enol–enal tautomerization. The developed reaction conditions tolerate a wide range of functional groups and display broad substrate scope.