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Conjugate addition – enantioselective protonation reactions

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ABSTRACT

The addition of nucleophiles to electron-deficient alkenes represents one of the more general and commonly used strategies for the convergent assembly of more complex structures from simple precursors. In this review the addition of diverse protic and organometallic nucleophiles to electron-deficient alkenes followed by enantioselective protonation is summarized. Reactions are first categorized by the type of electron-deficient alkene and then are further classified according to whether catalysis is achieved with chiral Lewis acids, organocatalysts, or transition metals.

No MeSH data available.


Hayashi’s enantioselective hydroarylation of diphenylphosphinylallenes.
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C39: Hayashi’s enantioselective hydroarylation of diphenylphosphinylallenes.

Mentions: In 2006, Hayashi and co-workers reported the first conjugate addition–enantioselective protonation of allenes 165 bearing a phosphine oxide (Scheme 39) [68]. Incorporation of the phosphine oxide allowed for selective protonation forming the less stabilized terminal chiral alkene 166 over the internal achiral isomer 167, an inherent challenge in the hydroarylation of terminal allenes. Electron-rich, neutral, and electron-poor arylboronic acids 47 added to alkyl (R = Me, Et, n-Bu) diphenylphosphinylallenes 165 in high yield and excellent enantioselectivity (85–94% yield, 98:2 to 99:1 er). With sterically bulky α-substituents (R = Ph, t-Bu), competitive formation of the achiral internal alkene was preferred.


Conjugate addition – enantioselective protonation reactions
Hayashi’s enantioselective hydroarylation of diphenylphosphinylallenes.
© Copyright Policy - Beilstein
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4979737&req=5

C39: Hayashi’s enantioselective hydroarylation of diphenylphosphinylallenes.
Mentions: In 2006, Hayashi and co-workers reported the first conjugate addition–enantioselective protonation of allenes 165 bearing a phosphine oxide (Scheme 39) [68]. Incorporation of the phosphine oxide allowed for selective protonation forming the less stabilized terminal chiral alkene 166 over the internal achiral isomer 167, an inherent challenge in the hydroarylation of terminal allenes. Electron-rich, neutral, and electron-poor arylboronic acids 47 added to alkyl (R = Me, Et, n-Bu) diphenylphosphinylallenes 165 in high yield and excellent enantioselectivity (85–94% yield, 98:2 to 99:1 er). With sterically bulky α-substituents (R = Ph, t-Bu), competitive formation of the achiral internal alkene was preferred.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

The addition of nucleophiles to electron-deficient alkenes represents one of the more general and commonly used strategies for the convergent assembly of more complex structures from simple precursors. In this review the addition of diverse protic and organometallic nucleophiles to electron-deficient alkenes followed by enantioselective protonation is summarized. Reactions are first categorized by the type of electron-deficient alkene and then are further classified according to whether catalysis is achieved with chiral Lewis acids, organocatalysts, or transition metals.

No MeSH data available.