A highly enantio- and diastereoselective [4 + 1]-annulation reaction between α,β-unsaturated imines and allylic carbonates has been realized under the catalysis of a novel hybrid P-chiral phosphine oxide-phosphine, providing enantioenriched polysubstituted 2-pyrrolines in good to excellent yields and up to 99% ee. Based on Han's methods, the catalyst featuring a sole P(O)-chirality in the molecule is readily accessible and represents a class of new chiral phosphine organocatalysts. In the plausible catalytic mechanism, an intramolecular Coulombic interaction between the in situ generated phosphonium cation and polar chiral P═O moiety may play a positive role.
In this work, a type of enantiopure chiral phosphines bearing a polar S=O sulfinyl group as the chiral unit in the molecule has been developed, which can be prepared in either enantiomeric form from commercially available materials by a three‐step route. The enantiopure chiral phosphines can catalyse enantiodivergent asymmetric [4+1] annulation reactions of α,β‐unsaturated imines and allylic carbonates, delivering polysubstituted pyrrolines in either enantiomeric form in up to 99% yield and up to 99% ee, and thus empower a method for dual stereo‐controlled synthesis of chiral pyrrolines. This work accordingly unveils a practical and predictable strategy to realize enantiodivergent synthesis.magnified image
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