Unsymmetric α,ω-Diol Oxidation into Aliphatic Hydroxyaldehydes: Active Organic Intermediates with Exceptionally High Value

Hydroxyaldehydes are terminally differentiated building blocks and key intermediates for organic synthesis. Unsymmetric oxidation of α,ω-diols to aliphatic hydroxyaldehydes is rarely developed due to the tremendous difficulties and challenges to avoid overoxidation. Here, we disclose a heterogeneous photocatalytic approach with Pt-loaded TiO₂ as a photocatalyst to realize the semioxidation of α,ω-diols to aliphatic hydroxyaldehydes. 6-Hydroxyhexanal is produced via photocatalytic dehydrogenation of 1,6-hexanediol at a rate of ca. 21.7 g/m²/h with selectivity higher than 96% and simultaneous generation of stoichiometric amounts of H₂. The absence of aggressive oxygen-based radical species, appropriately controlled oxidation capacity of photogenerated holes, low affinity of hydroxyaldehyde for photocatalysts in the suitable acetonitrile solvent matrix, and fine-tuned reaction temperature ensure that the oxidation of 1,6-hexanediol terminates at 6-hydroxyhexanal. This work reports on a conceptual breakthrough in photocatalytic interface design for high-value-added molecular synthesis via controlled surface redox reactions.