Enantioselective synthesis of P -chiral tertiary phosphine oxides with an ethynyl group via Cu(i)-catalyzed azide-alkyne cycloaddition

We report the highly enantioselective synthesis of -chiral tertiary phosphine oxides featuring an ethynyl group Cu(i)-catalyzed azide-alkyne cycloaddition. Newly developed chiral pyridinebisoxazolines (PYBOX) bearing a bulky C4 shielding group play an important role in achieving excellent enantiosel...

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Bibliographic Details
Published in:Chemical science (Cambridge) 2020-01, Vol.11 (1), p.97-106
Main Authors: Zhu, Ren-Yi, Chen, Long, Hu, Xiao-Si, Zhou, Feng, Zhou, Jian
Format: Article
Language:English
Subjects:
Alkynes
Covalent bonds
Crystallography
Cycloaddition
Enantiomers
Oxides
Phosphine oxide
Phosphines
Remote control
Shielding
Synthesis
Time dependence
Triazoles
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Summary:We report the highly enantioselective synthesis of -chiral tertiary phosphine oxides featuring an ethynyl group Cu(i)-catalyzed azide-alkyne cycloaddition. Newly developed chiral pyridinebisoxazolines (PYBOX) bearing a bulky C4 shielding group play an important role in achieving excellent enantioselectivity while suppressing side bis-triazoles formation in desymmetrizing prochiral diethynylphosphine oxides. Notably, by tuning the size of the C4 shielding group, it is possible to achieve excellent remote enantiofacial control in desymmetrizing phosphole oxide-diynes with the prochiral -center farther from the ethynyl group . Time-dependent enantioselectivity is observed for these desymmetric CuAAC reactions, suggesting a synergic combination of a desymmetrization and a kinetic resolution, and our ligands prove to be better than unmodified PYBOX in both steps. This finding contributes to a highly enantioselective kinetic resolution of racemic ethynylphosphine oxides. The resulting chiral ethynylphosphine oxides are versatile -chiral synthons, which can undergo a number of diversifying reactions to enrich structural diversity.
ISSN:2041-6520
2041-6539
DOI:10.1039/c9sc04938j