Crown-cation complex effects. 8. Reactions of crown ether activated tert-butoxide ion

DiBiase, Stephen A.; Gokel, George W.

doi:10.1021/jo00397a015

Cited by 43 publications

(15 citation statements)

References 11 publications

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“…Apart from the Heck-type synthesis reported by Nilsson et al 17 the other existing methodologies to construct such interesting framework, 10,11,34 which involve (i) TiCl 4 / Sm-promoted reductive coupling of benzophenones and nitriles, 35 (ii) oxidative nucleophilic addition of diphenyl methyl anion to benzaldehyde, 36 (iii) pinacolinic rearrangement 37 and (iv) nucleophilic substitution with benzotriazole derived carbanions, 38 generally present serious limitations concerning tolerability of functional groups and restricted substitution patterns at the precursors.…”

Section: A-monoarylation Of Deoxybenzoins Under Heterogeneous Conditionsmentioning

confidence: 99%

Towards a facile synthesis of triarylethanones: palladium-catalyzed arylation of ketone enolates under homogeneous and heterogeneous conditions

et al. 2004

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Section: A-monoarylation Of Deoxybenzoins Under Heterogeneous Conditionsmentioning

confidence: 99%

Towards a facile synthesis of triarylethanones: palladium-catalyzed arylation of ketone enolates under homogeneous and heterogeneous conditions

et al. 2004

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“…One of the most economically viable methods for their preparation is nucleophilic fluorination of alkyl halides or sulfonate esters using alkaline fluorides. Because the Crown ethers and cryptands make stable complexes with metal ions M + , and thus increase the dissociation of MY into ions pairs and provide highly reactive, unsolvated ("naked") anions Y: − [271][272][273][274]. The nature of the crown ether or cryptand can be chosen to fit M + the best and for an optimal catalytic effect.…”

Section: Scheme 39 Example Of Phase-transfer Catalysis (Ptc)mentioning

confidence: 99%

“…Crown ethers derived from monosaccharides also allow asymmetric phase transfer reactions [279][280][281][282]. Crown ethers and cryptands make stable complexes with metal ions M + , and thus increase the dissociation of MY into ions pairs and provide highly reactive, unsolvated ("naked") anions Y: − [271][272][273][274]. The nature of the crown ether or cryptand can be chosen to fit M + the best and for an optimal catalytic effect.…”

Section: Scheme 39 Example Of Phase-transfer Catalysis (Ptc)mentioning

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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“…This conclusion can be compared to Gokel's work which had shown that the presence of 18-crown-6 rendered potassium tert-butoxide relatively nucleophilic in THF. 8 In the synthesis of the phenoltriallyl dendron A (Scheme 2), a complex 8-step reaction, it is not necessary to add a salt. The first reason is that KBr is generated in situ.…”

Section: Salt Effect: Comparison Of Various Saltsmentioning

confidence: 99%

“…For instance, its nucleophilic character can sometimes be expressed, as for instance in the presence of 18-crown-6 ether that segregates the potassium cation, providing an enhanced reactivity of the anion. 8 Nevertheless, potassium tert-butoxide is little known as a nucleophile despite these seminal studies.…”

Section: Introductionmentioning

confidence: 99%

Can t-BuOK be a good nucleophile? An ion-pairing answer. Cleavage of aryl ethers in their cationic iron complexes

Astruc¹,

Djankovitch²,

Aranzaes³

2006

Arkivoc

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Crown-cation complex effects. 8. Reactions of crown ether activated tert-butoxide ion

Cited by 43 publications

References 11 publications

Towards a facile synthesis of triarylethanones: palladium-catalyzed arylation of ketone enolates under homogeneous and heterogeneous conditions

Towards a facile synthesis of triarylethanones: palladium-catalyzed arylation of ketone enolates under homogeneous and heterogeneous conditions

Organocatalysis: Fundamentals and Comparisons to Metal and Enzyme Catalysis

Can t-BuOK be a good nucleophile? An ion-pairing answer. Cleavage of aryl ethers in their cationic iron complexes

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