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Catalytic asymmetric cycloadditions of ambident Pd-containing dipolar species with nucleophilic dipolarophiles, namely, inverse electron-demand cycloadditions, are challenging and under-developed. Possibly, the inherent linear selectivity of Pd-catalyzed intermolecular allylations and the lack of efficient chiral ligands are responsible for this limitation. Herein, two cycloadditions of such intermediates with deconjugated butenolides and azlactones were firstly accomplished by using a novel chiral hybrid P,S-ligand and H-bonding direction. By doing so, highly functionalized, optically active dihydroquinol-2-ones were produced with generally high reaction efficiency and selectivity (35 examples, 54->99% yields with up to 95% ee and >95:5 dr). DFT calculations were performed to explain the high selectivities.
PMID: 31144410 [PubMed - as supplied by publisher]