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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.


Feng’s enantioselective addition of pyrazoles to α-substituted vinyl ketones.
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C26: Feng’s enantioselective addition of pyrazoles to α-substituted vinyl ketones.

Mentions: The Feng group has reported the conjugate addition of pyrazoles to α-substituted aromatic vinyl ketones followed by enantioselective protonation of the enolate intermediate using an N,N’-dioxide–Sc(III) catalyst system (Scheme 26) [51]. During optimization, the authors found that incorporation of bulky amides into ligand 113 was crucial for achieving high enantioselectivity. A wide variety of α-aryl vinyl ketones 112 were effective substrates, and only when R1 was methyl did the enantioselectivity drop below 92:8 er to 80:20 er (Scheme 26). The authors also investigated a number of pyrazole nucleophiles 111, which all reacted with high enantioselectivity, including pyrazoline 111e (Scheme 26).


Conjugate addition – enantioselective protonation reactions
Feng’s enantioselective addition of pyrazoles to α-substituted vinyl ketones.
© Copyright Policy - Beilstein
Related In: Results  -  Collection

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

C26: Feng’s enantioselective addition of pyrazoles to α-substituted vinyl ketones.
Mentions: The Feng group has reported the conjugate addition of pyrazoles to α-substituted aromatic vinyl ketones followed by enantioselective protonation of the enolate intermediate using an N,N’-dioxide–Sc(III) catalyst system (Scheme 26) [51]. During optimization, the authors found that incorporation of bulky amides into ligand 113 was crucial for achieving high enantioselectivity. A wide variety of α-aryl vinyl ketones 112 were effective substrates, and only when R1 was methyl did the enantioselectivity drop below 92:8 er to 80:20 er (Scheme 26). The authors also investigated a number of pyrazole nucleophiles 111, which all reacted with high enantioselectivity, including pyrazoline 111e (Scheme 26).

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.