Cross-benzoin Reaction Research Articles

Asymmetric synthesis of functionalized cyclopentanones via a multicatalytic secondary amine/N-heterocyclic carbene catalyzed cascade sequence.

A one-pot, asymmetric multicatalytic formal [3+2] reaction between 1,3-dicarbonyls and alpha,beta-unsaturated aldehydes is described. The multicatalytic process involves a secondary amine catalyzed Michael addition followed by a N-heterocyclic carbene catalyzed intramolecular crossed benzoin reaction to afford densely functionalized cyclopentanones with high enantioselectivities. The reaction proceeds with a variety of alkyl and aryl enals as well as a range of 1,3-dicarbonyls (diketones and beta-ketoesters). The functionalized products are obtained from cheap, readily available starting materials in a rapid and efficient manner in a one-pot, one-step operation.

Enantioselective, Cyclopentene-Forming Annulations via NHC-Catalyzed Benzoin−Oxy-Cope Reactions

Chiral N-heterocyclic carbene catalysts generated from triazolium salts promote the cyclopentene-forming annulation of α,β-unsaturated aldehydes and 4-oxoenoates with excellent levels of enantioinduction and preference for the cis-1,3,4-trisubstituted cyclopentene diastereomer. Although the observed products could arise by conjugate additions of catalytically generated homoenolates, our mechanistic and stereochemical investigations strongly support a novel reaction manifold featuring an intermolecular crossed-benzoin reaction and an NHC-catalyzed oxy-Cope rearrangement.

Asymmetric Synthesis of Chromanones via N‐Heterocyclic Carbene Catalyzed Intramolecular Crossed‐Benzoin Reactions.

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Asymmetric Synthesis of Chromanones via N-Heterocyclic Carbene Catalyzed Intramolecular Crossed-Benzoin Reactions

The enantioselective synthesis of 3-hydroxy-4-chromanones bearing a quaternary stereocenter via an N-heterocyclic ­carbene catalyzed intramolecular crossed-benzoin reaction is described.

Intramolecular Crossed-Benzoin Reactions Catalyzed by Chiral Triazolium Salts

Intramolecular Crossed-Benzoin Reactions Catalyzed by Chiral Triazolium Salts

Asymmetric Intramolecular Crossed-Benzoin Reactions by N-Heterocyclic Carbene Catalysis

Geglückte Kreuzung: Mit chiralen N-heterocyclischen Carbenen als Katalysatoren ließen sich bei der Erzeugung eines quartären Stereozentrums in α-hydroxysubstituierten Tetralonen (siehe Bild) mithilfe einer enantioselektiven intramolekularen gekreuzten Benzoinreaktion ausgezeichnete asymmetrische Induktionen und sehr gute Ausbeuten erzielen. Die Synthese der entsprechenden α-Hydroxyindanone mit guten ee-Werten ist auf diesem Weg ebenfalls möglich.

Generation of Acyl Anion Equivalents from Acylphosphonates via Phosphonate−Phosphate Rearrangement: A Highly Practical Method for Cross-Benzoin Reaction

[reactions: see text] Acylphosphonates are potent acyl anion precursors that generate acyl anion equivalents under the promotion of cyanide anion via phosphonate-phosphate rearrangement. These anions readily react with aldehydes to provide cross-benzoin products. In this way it is possible to synthesize a variety of aromatic-aromatic, aromatic-aliphatic, and aliphatic-aromatic benzoins. Moreover the reaction of benzoylphosphonate with potent electrophile 2,2,2-trifluoroacetophenone provided the corresponding aldehyde-ketone coupling product in high yield.

Metallophosphite‐Induced Nucleophilic Acylation of α,β‐Unsaturated Amides: Facilitated Catalysis by a Diastereoselective Retro [1,4] Brook Rearrangement

Metallophosphite‐Induced Nucleophilic Acylation of α,β‐Unsaturated Amides: Facilitated Catalysis by a Diastereoselective Retro [1,4] Brook Rearrangement