Organic Letters· 2026Q1
Overcoming Reversibility: Borrowing Hydrogen Enables Enantioselective Intermolecular Oxa-Michael Addition to α,β-Unsaturated Aldehydes
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- 2026year
Short summary
A multicatalytic borrowing hydrogen strategy combines iridium catalysis and organocatalysis to achieve enantioselective intermolecular oxa-Michael addition of oximes and alcohols to α,β-unsaturated aldehydes, overcoming reversibility issues.
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Key points
- A borrowing hydrogen (BH) strategy was developed for enantioselective intermolecular oxa-Michael addition to α,β-unsaturated aldehydes.
- The strategy combines iridium-catalyzed reversible dehydrogenation/hydrogenation with organocatalyzed iminium-type activation.
- The method enables the addition of oximes and alcohols to allylic alcohols under mild conditions (25°C).
- Mechanistic studies show the BH pathway shifts equilibrium and limits racemization by suppressing retro-oxa-Michael addition.
AI-generated from the title and abstract; the full text is not read.
Abstract
Abstract Chiral 1,3-dioxygenated motifs are key scaffolds in bioactive natural products, yet their synthesis via intermolecular oxa-Michael addition to α,β-unsaturated aldehydes remains challenging notably due to the high reversibility of the oxygenated nucleophile addition. This study presents a multicatalytic borrowing hydrogen (BH) strategy combining iridium-catalyzed reversible dehydrogenation/hydrogenation and enantioselective organocatalyzed iminium-type activation to overcome these limitations. Under mild conditions (25°C), the approach enables the enantioselective oxa-Michael addition of oxygenated nucleophiles (oximes and alcohols) to allylic alcohols, directly delivering key enantioenriched alcohols. Mechanistic studies confirm that the BH pathway displaces the equilibrium toward the alcohol product, limiting racemization at the aldehyde level occurring through rapid retro-oxa-Michael addition. This work demonstrates that BH catalysis can unlock otherwise inaccessible transformations starting directly from aldehydes, offering a sustainable and efficient route to complex chiral molecules.
The authors' abstract, as published at the source. Organic Letters, 2026 · DOI ↗
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Field: Inorganic Chemistry
Inorganic ChemistryChemistry