Enzyme-inspired single-molecule photocatalyst enables singlet-oxygen-driven asymmetric epoxidation and sulfoximination

Le résumé fourni par la source

The development of catalytic systems for the enantioselective epoxidation of sterically hindered trisubstituted alkenes using molecular oxygen (O₂) as the terminal oxidant remains a formidable challenge. Here, we report a biomimetic bifunctional photocatalyst that integrates a chiral manganese center and a covalently tethered anthraquinone photosensitizer within a single molecular scaffold. This unified design emulates the enzymatic principle of spatially coupled oxygen activation and chiral induction. Under visible light and ambient O₂, the catalyst enables the asymmetric epoxidation of challenging trisubstituted alkenes, including cyclic sulfones and linear α,β-unsaturated carbonyls, in up to 99% enantiomeric excess (ee), and also facilitates the efficient conversion of sulfilimines to (chiral) sulfoximines. Mechanistic studies reveal a cascade involving singlet-oxygen-mediated oxidation, oxidative decarboxylation, and acid-assisted O–O bond heterolysis to generate a high-valent Mn⁴⁺=O species as the key active intermediate. By unifying light harvesting, O₂ activation, and asymmetric catalysis in a precious-metal-free platform, this work establishes a versatile, sustainable strategy for the selective oxidation of traditionally recalcitrant substrates. The development of catalytic systems for the enantioselective epoxidation of sterically hindered trisubstituted alkenes and the oxidation of sulfilimines to sulfoximines using molecular oxygen (O₂) as the terminal oxidant remains a formidable challenge. Here, the authors report a biomimetic bifunctional photocatalyst that integrates a chiral manganese center and a covalently tethered anthraquinone photosensitizer within a single molecular scaffold.

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