Transesterification/Acylation of Secondary Alcohols Mediated by<i> N</i>-Heterocyclic Carbene Catalysts

Singh, Rohit; Kissling, Rebecca M.; Letellier, Marie; Nolan, Steven P.

doi:10.1021/jo035431p

Cited by 178 publications

(67 citation statements)

References 18 publications

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“…397,398 The carbene was combined with stoichiometric amounts of the required reagents in the presence of molecular sieves. [399][400][401] In the first case, catalysis with imidazol-2-ylidenes in the presence of primary alcohols, resulted values for TON and TOF of 17-19 and 1 h ) but proceeds irreversibly due to the release of acetaldehyde.…”

Section: Catalysis By Carbenesmentioning

confidence: 99%

Synthesis and properties of heteroaromatic carbenes of the imidazole and triazole series and their fused analogues

Коротких¹,

Cowley²,

Clyburne³

et al. 2017

Arkivoc

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Section: Catalysis By Carbenesmentioning

confidence: 99%

Synthesis and properties of heteroaromatic carbenes of the imidazole and triazole series and their fused analogues

Коротких¹,

Cowley²,

Clyburne³

et al. 2017

Arkivoc

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“…For these reactions, the usual catalysts are Brønsted mineral acids (H 3 PO 4 , H 2 SO 4 , HCl) [24][25][26], and organic acids such as MeSO 3 H and p-toluenesulfonic acid (TsOH) [27], alkoxides such as NaOR, KOR, ROMgBr [28][29][30][31][32], Lewis bases such as 4-dimethylaminopyridine (DMAP) [33,34], 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) [35], Lewis acids such as BX 3 [36], or AlCl 3 [37], amphoteric Catalysts 2016, 6, 128 5 of 65 compounds (compounds able to react either as acids or bases) such as Bu 3 SnOR [38][39][40][41], perfluorotin oxides [42], Al(OR) 3 [43,44], titanium oxides chlorides [45][46][47][48] or palladium oxides [49,50]. More recently, diaminocarbenes have been introduced as catalysts as well [51][52][53][54]. Mechanisms of the gas-phase acyl group transfers involve tetrahedral adducts as intermediates or transition states, as suggested by quantum calculations [55].…”

Section: Acyl Group Transfersmentioning

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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“…Since stable carbenes are highly basic compounds (pKa 21-28) they have also been suggested as catalysts for the transesterification reaction. [2][3][4][5][6][7][8] The latter reaction is typically carried out at room temperature in the presence of 0.5-5.0 mol% of carbenes and molecular sieves. The efficiencies of the catalysts can be estimated on the basis of the values of TON and TOF.…”

Section: Introductionmentioning

confidence: 99%

Highly efficient carbene and polycarbene catalysis of the transesterification reaction

Marichev¹,

Коротких²,

Cowley³

et al. 2017

Arkivoc

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Highly efficient carbene and polycarbene catalysis of the transesterification reaction of ethyl benzoate in methanol has been observed and results in values of TON as high as 4000-6150 at a molar ratio of ester to methanol of 1:18 at room temperature. The most effective catalysts were found to be the individual carbenes or in situ generated carbenes, namely adamantyl and aromatic substituted cyclic compounds and polymeric carbenes. None of the reactions requires the use of molecular sieves. The polymeric imidazol-2-ylidene catalyst was used for the efficient production of biodiesel fuel from sunflower oil.

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Transesterification/Acylation of Secondary Alcohols Mediated by N-Heterocyclic Carbene Catalysts

Abstract: N-Heterocyclic carbenes (NHC) are efficient catalysts for transesterification/acylation reactions involving secondary alcohols. The catalytic transformations are carried out employing low catalyst loadings in convenient reaction times at room temperature.

Cited by 178 publications

References 18 publications

Synthesis and properties of heteroaromatic carbenes of the imidazole and triazole series and their fused analogues

Synthesis and properties of heteroaromatic carbenes of the imidazole and triazole series and their fused analogues

Organocatalysis: Fundamentals and Comparisons to Metal and Enzyme Catalysis

Highly efficient carbene and polycarbene catalysis of the transesterification reaction

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