Cyanide‐Catalyzed Additions of Acyl Phosphonates to Aldehydes: A New Acyl Donor for Benzoin‐Type Reactions

Bausch, Cory C.; Johnson, Jeffrey S.

doi:10.1002/adsc.200505097

Cited by 63 publications

(7 citation statements)

References 13 publications

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“…Heterocyclic aldehydes provided the expected products 3e and 3g , albeit contaminated with isomeric benzoins 3f and 3h (Table , entries 5−8). This concurrent regioisomerization process was also pointed out by Johnson and co-workers . Whereas lowering the temperature (0 °C) provided the expected products without isomer contamination, increasing the catalyst load (30%) quickly furnished the isomeric products.…”

supporting

confidence: 66%

“…We envisioned that the typical nucleophilic catalysis of benzoin and Stetter reactions might promote acylphosphonates to generate an appropriate concentration of the corresponding acyl anion equivalents that are sufficiently nucleophilic in order to participate in the reactions with electrophiles. It is very important to note that Johnson and co-workers very recently reported the viability of this approach in the synthesis of a variety of aromatic−aromatic cross-benzoin products 3 from aromatic acylphosphonates, with [18-crown-6/KCN] complex as catalyst in diethyl ether providing the optimal conditions (Scheme ) . Morover Kurihara reported stoichiometric strong base deprotonation of α-cyanophosphates generating cyano-phosphate anions 1b that react with a variety of electrophiles including aldehydes to provide 3 …”

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confidence: 99%

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

Reis

et al. 2005

J. Org. Chem.

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[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.

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confidence: 66%

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confidence: 99%

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

Reis

et al. 2005

J. Org. Chem.

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“…The proposed mechanism (Scheme 49) implies a cyanide-promoted [1,2]-Brook rearrangement 88 → 89 [337,338]. Acyl phosphonates also undergo cyanide-catalyzed additions to aldehydes [339]. A strategy utilizing N-heterocyclic carbenes (NHCs) derived from thiazolium salts has been developed for the generation of carbonyl anions from acylsilanes [340].…”

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confidence: 99%

Organocatalysis: Fundamentals and Comparisons to Metal and Enzyme Catalysis

et al. 2016

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Catalysis fulfills the promise that high-yielding chemical transformations will require little energy and produce no toxic waste. This message is carried by the study of the evolution of molecular catalysis of some of the most important reactions in organic chemistry. After reviewing the conceptual underpinnings of catalysis, we discuss the applications of different catalysts according to the mechanism of the reactions that they catalyze, including acyl group transfers, nucleophilic additions and substitutions, and C-C bond forming reactions that employ umpolung by nucleophilic additions to C=O and C=C double bonds. We highlight the utility of a broad range of organocatalysts other than compounds based on proline, the cinchona alkaloids and binaphthyls, which have been abundantly reviewed elsewhere. The focus is on organocatalysts, although a few examples employing metal complexes and enzymes are also included due to their significance. Classical Brønsted acids have evolved into electrophilic hands, the fingers of which are hydrogen donors (like enzymes) or other electrophilic moieties. Classical Lewis base catalysts have evolved into tridimensional, chiral nucleophiles that are N-(e.g., tertiary amines), P-(e.g., tertiary phosphines) and C-nucleophiles (e.g., N-heterocyclic carbenes). Many efficient organocatalysts bear electrophilic and nucleophilic moieties that interact simultaneously or not with both the electrophilic and nucleophilic reactants. A detailed understanding of the reaction mechanisms permits the design of better catalysts. Their construction represents a molecular science in itself, suggesting that sooner or later chemists will not only imitate Nature but be able to catalyze a much wider range of reactions with high chemo-, regio-, stereo-and enantioselectivity. Man-made organocatalysts are much smaller, cheaper and more stable than enzymes.

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“…Recently, we and others have shown that acyl phosphonates are potent acyl anion precursors and undergo nucleophile-promoted phosphonate−phosphate rearrangement to provide the corresponding acyl anion equivalents as reactive intermediates. Acyl phosphonates 1 , which are easily synthesized from acyl chloride and trialkyl phosphite in high yields, as the acyl anion precursors, and aldehydes as the electrophiles in the presence of a cyanide catalyst provide cross-benzoin products.…”

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confidence: 99%

Addition of Trifluoromethyltrimethylsilane to Acyl Phosphonates: Synthesis of TMS-Protected 1-Alkyl-1-trifluoromethyl-1-hydroxyphosphonates and 1-Aryldifluoroethenyl Phosphates

Demir

Eymür

2007

J. Org. Chem.

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Addition reactions of nucleophilic CF3TMS to acyl phosphonates were investigated. Various acyl phosphonates reacted readily with CF3TMS in the presence of K2CO3 in DMF at rt to give 1-alkyl-2,2,2-trifluoro-1-trimethylsilyloxyethylphosphonate in 70-90% yields. When benzoyl phosphonates were used as starting material, after addition of CF3, the formed alcoholate undergoes phosphonate-phosphate rearrangement to form the acyl anion, followed by elimination of F- to give 1-aryldifluoroethenyl phosphates in 87-97% yields. As a representative example, vinylphosphate 6a was converted into 2,2-difluoro-1-phenylethanone 7 with 6 N HCl/EtOH/reflux or CAN/NaOH/MeOH/0 degrees C in 82-90% yields.

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Cyanide‐Catalyzed Additions of Acyl Phosphonates to Aldehydes: A New Acyl Donor for Benzoin‐Type Reactions

Cited by 63 publications

References 13 publications

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

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

Organocatalysis: Fundamentals and Comparisons to Metal and Enzyme Catalysis

Addition of Trifluoromethyltrimethylsilane to Acyl Phosphonates: Synthesis of TMS-Protected 1-Alkyl-1-trifluoromethyl-1-hydroxyphosphonates and 1-Aryldifluoroethenyl Phosphates

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