- Efficient Enzymatic Preparation of Flavor Esters in Water
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A straightforward biocatalytic method for the enzymatic preparation of different flavor esters starting from primary alcohols (e.g., isoamyl, n-hexyl, geranyl, cinnamyl, 2-phenethyl, and benzyl alcohols) and naturally available ethyl esters (e.g., formate, acetate, propionate, and butyrate) was developed. The biotransformations are catalyzed by an acyltransferase from Mycobacterium smegmatis (MsAcT) and proceeded with excellent yields (80-97%) and short reaction times (30-120 min), even when high substrate concentrations (up to 0.5 M) were used. This enzymatic strategy represents an efficient alternative to the application of lipases in organic solvents and a significant improvement compared with already known methods in terms of reduced use of organic solvents, paving the way to sustainable and efficient preparation of natural flavoring agents.
- Perdomo, Igor Chiarelli,Gianolio, Stefania,Pinto, Andrea,Romano, Diego,Contente, Martina Letizia,Paradisi, Francesca,Molinari, Francesco
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p. 6517 - 6522
(2019/06/20)
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- Zirconocene-catalyzed direct (trans)esterification of acyl acids (esters) and alcohols in a strict 1:1 ratio under solvent-free conditions
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A highly efficient way for the direct (trans)esterification of acyl acids (esters) and alcohols in a strict 1:1 ratio using a zirconocene complex (1, 1 mol%), a strong Lewis acid of good water tolerance, as a catalyst under solvent-free conditions has been developed. A wide range of acid and alcohol (esters) substrates undergo (trans)esterification to produce carboxylic ester motifs in moderate to good or excellent yields with good functional tolerance, such as that towards C-Br as well as CC and CC bonds. And complex 1 can be recycled six times without showing a significant decline in catalytic efficiency. It was demonstrated that cyclandelate, which is used to treat high blood pressure as well as heart and blood-vessel diseases, can be directly synthesized on a gram scale with 81% yield (6.70 g) using complex 1.
- Tang, Zhi,Jiang, Qiutao,Peng, Lifen,Xu, Xinhua,Li, Jie,Qiu, Renhua,Au, Chak-Tong
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supporting information
p. 5396 - 5402
(2017/11/22)
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- Transfer Hydro-dehalogenation of Organic Halides Catalyzed by Ruthenium(II) Complex
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A simple and efficient Ru(II)-catalyzed transfer hydro-dehalogenation of organic halides using 2-propanol solvent as the hydride source was reported. This methodology is applicable for hydro-dehalogenation of a variety of aromatic halides and α-haloesters and amides without additional ligand, and quantitative yields were achieved in many cases. The potential synthetic application of this method was demonstrated by efficient gram-scale transformation with catalyst loading as low as 0.5 mol %.
- You, Tingjie,Wang, Zhenrong,Chen, Jiajia,Xia, Yuanzhi
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p. 1340 - 1346
(2017/02/10)
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- Reductive dehalogenation method of organic halide
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The invention discloses a reductive dehalogenation method of an organic halide. In the inert gas atmosphere, the organic halide shown as the formula I or the formula II is subjected to reductive dehalogenation to generate an organic compound shown as the formula III or the formula IV (the formulas are shown as the description) in the presence of a catalyst, alkali and a solvent, wherein the reaction temperature is controlled to 90-100 DEG C. The reductive dehalogenation method has the advantages that the range of substrates is widened; the solvent in use does not need extra phosphorous ligands, the price is relatively cheap, and the consumption can be greatly reduced to 0.1 mol%; the solvent in use serves as a hydrogen source and reacts, the operation is simple, a lot reactions can reach quantitative yields, and when the reactions are scaled up to gram level reactions, almost quantitative yields can still be achieved.
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Paragraph 0087; 0088; 0089; 0090; 0091; 0092
(2017/08/28)
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- A microwave-assisted highly practical chemoselective esterification and amidation of carboxylic acids
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The ubiquitousness of esters and amide functionalities makes their coupling reaction one of the most sought-after organic transformations. Herein, we have described an efficient microwave-assisted synthesis of esters and amides. Soluble triphenylphosphine, in conjugation with molecular iodine, gave the desired products without the requirement for a base/catalyst. In addition, a solid-phase synthetic route is incorporated for the said conversion, which has added advantages over solution-phase pathways, such as low moisture sensitivity, easy handling, isolation of the product by simple filtration, and reusability. In short, our method is simple, mild, green, and highly chemoselective in nature.
- Pathak, Gunindra,Das, Diparjun,Rokhum, Lalthazuala
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p. 93729 - 93740
(2016/10/21)
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- N-Heterocyclic carbene-mediated redox condensation of alcohols
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N-Heterocyclic carbenes (NHCs) with a variety of oxidants promote the Mitsunobu-type coupling reactions of alcohols with phenols, carboxylic acids, and phthalimide. Experiments using a chiral alcohol indicate that these reactions proceed via SN1 or SN2 pathways depending on the polarity of the used solvents. The NHCs are consumed as reducing reagents to form their oxides as readily separable byproducts.
- Kato, Terumasa,Matsuoka, Shin-Ichi,Suzuki, Masato
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supporting information
p. 8569 - 8572
(2016/07/13)
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- Efficient O-Acylation of Alcohols and Phenol Using Cp2TiCl as a Reaction Promoter
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A method has been developed for the conversion of primary, secondary, and tertiary alcohols, and phenol, into the corresponding esters at room temperature. The method uses a titanium(III) species generated from a substoichiometric amount of titanocene dichloride together with manganese(0) as a reductant, as well as methylene diiodide. It involves a transesterification from an ethyl ester, or a reaction with an acyl chloride. A radical mechanism is proposed for these transformations.
- Durán-Pe?a, María Jesús,Botubol-Ares, José Manuel,Hanson, James R.,Hernández-Galán, Rosario,Collado, Isidro G.
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supporting information
p. 3584 - 3591
(2016/07/28)
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- Recyclable hypervalent iodine(III) reagent iodosodilactone as an efficient coupling reagent for direct esterification, amidation, and peptide coupling
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A hypervalent iodine(III) reagent plays a novel role as an efficient coupling reagent to promote the direct condensation between carboxylic acids and alcohols or amines to provide esters, macrocyclic lactones, amides, as well as peptides without racemization. The regeneration of iodosodilactone (1) can also be readily achieved. The intermediate acyloxyphosphonium ion C from the activation of a carboxylic acid is thought to be involved in the present esterification reaction.
- Tian, Jun,Gao, Wen-Chao,Zhou, Dong-Mei,Zhang, Chi
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supporting information; experimental part
p. 3020 - 3023
(2012/08/07)
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- Synthesis of aromatic alcohols and their alkanoic acid esters
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The reaction of benzene with ethylene and propylene oxides in a helium atmosphere with aluminum chloride as a catalyst and the esterification of the resulting alcohols with saturated monocarboxylic acids in the presence of the heterogeneous catalyst KU-2-8 were studied. Pleiades Publishing, Inc., 2006.
- Mamedov
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p. 408 - 410
(2008/02/03)
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- Scope and mechanistic insights into the use of tetradecyl(trihexyl) phosphonium bistriflimide: A remarkably selective ionic liquid solvent for substitution reactions
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A survey of substitution reactions conducted in a phosphonium bistriflimide ionic liquid is presented. The results demonstrate high selectivity favoring substitution over typically competitive elimination and solvolytic processes even when challenging secondary and tertiary electrophiles are employed. The first reports of Kornblum substitution reactions in an ionic liquid are described that proceed with very high chemoselectivity in favor of nitro over nitroso products and elimi nation side products. The structure-reactivity study indicates that these reactions proceed through a narrow spectrum of pathways ranging from straight SN2 to a preassociation pathway along a saddle point that approaches the SN1 limit. The barrier to the formation of dissociated carbocations is attributed to the structural features of this ionic liquid that favor intervention of the associated nucleophile over dissociation, also preventing cross over to E1 processes. The lack of any basic entity in the phosphonium bistriflimide ionic liquid appears to prevent any potential base-mediated elimination reactions, which makes this a highly selective medium for use in general substitution reactions.
- McNulty, James,Nair, Jerald J.,Cheekoori, Sreedhar,Larichev, Vladimir,Capretta, Alfredo,Robertson
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p. 9314 - 9322
(2007/10/03)
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- Lanthanide(III) tosylates as new acylation catalysts
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Lanthanide(III) complexes of p-toluenesulfonic acid (Ln(TOS)3) were prepared, characterized, and examined as catalysts for the acetylation of various alcohols in acetic acid solution. Examination of a series of Ln(TOS)3 catalysts in the acetylation of 2-phenylethanol revealed a clear correlation between the ionic radius of the lanthanide(III) ion and the yield of the reaction, with the heavier lanthanides being more effective. In the presence of 5 mol-% of Yb(TOS)3, a quantitative conversion of phenethyl alcohol to phenethyl acetate was achieved within 18 hours at 50°C. Faster reaction was obtained under reflux conditions, in which case acetylation was complete within 30 minutes and in the presence of only 2 mol-% of the Yb(TOS)3 catalyst. The Yb(TOS)3 catalyst was effective for acetylation of a range of primary, secondary, and tertiary alcohols. The Yb(TOS)3 catalyst was also effective for acylation of phenethyl alcohol with propionic acid and cyclohexanecarboxylic acid. The catalysts could be easily recovered and reused for further acetylation, with no apparent change in selectivity or efficiency. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
- Parac-Vogt, Tatjana N.,Deleersnyder, Karen,Binnemans, Koen
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p. 1810 - 1815
(2007/10/03)
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- A mild esterification process in phosphonium salt ionic liquid
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A general, high yielding procedure is described for the esterification of carboxylic acids through carboxylate alkylation in phosphonium salt ionic liquid.
- McNulty, James,Cheekoori, Sreedhar,Nair, Jerald J.,Larichev, Vladimir,Capretta, Alfredo,Robertson, Al J.
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p. 3641 - 3644
(2007/10/03)
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- Zn(ClO4)2·6H2O as a Powerful Catalyst for a Practical Acylation of Alcohols with Acid Anhydrides
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A new protocol for the acylation of alcohols with anhydrides in the presence of Zn(ClO4)2·6H2O as the catalyst is reported. The activity of Zn(ClO4)2· 6H2O has been proven to be superior to that exerted by dry Mg(ClO4)2 and by metal triflates. Its efficiency allows reactions between poorly reactive substrates, such as sterically hindered tertiary alcohols and aromatic anhydrides, All of the reactions were carried out at a 1:1.05 alcohol/anhydride ratio. These conditions are extremely convenient from a practical and economic point of view, since they avoid wasting reagents and allow a simple workup procedure. The catalytic action of Zn(ClO4)2·6H2O is so specific for the activation of the anhydrides, that acid-sensitive functionalities and the stereochemical configuration of the starting materials remain unaltered in the esterification process. In all cases, the acylated products are quantitatively obtained in pure form. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Bartoli, Giuseppe,Bosco, Marcella,Dalpozzo, Renato,Marcantoni, Enrico,Massaccesi, Massimo,Sambri, Letizia
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p. 4611 - 4617
(2007/10/03)
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- Microwave oven synthesis of esters promoted by imidazole
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Using imidazole as promotion agent, primary, secondary and phenolic alcohol compounds were esterified with aliphatic and aromatic carboxylic acid anhydrides. Heating a ternary mixture of alcohol, anhydride and imidazole in an unmodified microwave oven produced esters in low to high yields, depending on the steric bulk of the alcohol.
- Hirose, Takuji,Kopek, Benjamin G.,Wang, Zhao-Hui,Yusa, Ritsuko,Baldwin, Bruce W.
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p. 1831 - 1833
(2007/10/03)
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- Efficient liquid phase acylation of alcohols over basic ETS-10 molecular sieves
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Acylation of alcohols with acetic acid can be carried out efficiently in the liquid phase over microporous titanosilicate ETS-10-type catalysts. The reaction was studied over ETS-10 exchanged with, Li, Na, K, Rb, Cs, Ba and H ions. Activity for acylation of primary alcohols depends on the exchanged alkali ion and increases in the order LiNaKBa~H~Rb~Cs-ETS-10. These molecular sieves are also suitable for the acylation of secondary alcohols and esterification with long chain carboxylic acids.
- Waghmode, Suresh B.,Thakur, Vinay V.,Sudalai, Arumugam,Sivasanker, Subramanian
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p. 3145 - 3147
(2007/10/03)
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- Organic Reducing Agents. Reduction of Electron Deficient Bromides by 1,2,2,6,6-Pentamethylpiperidine (PMP)/Mercaptoethanol
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1,2,2,6,6-pentamethylpiperidine (PMP) is shown to be an effective reducing agent for the radical chain conversion of primary bromoesters in these reactions to the corresponding esters.The problem of inefficient reduction of tertiary bromoesters in these reactions has been overcome by the addition of an alkyl thiol which mediates the hydrogen atom transfer between the two hindered alkyl centers.
- Amoli, Maryam,Workentin, Mark S.,Wayner, Danial D. M.
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p. 3997 - 4000
(2007/10/02)
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- Organic Reducing Agents: Some Radical Chain Reactions of Ketyl and 1,3-Dioxolanyl Radicals with Activated Bromides
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The radical chain reduction of primary and secondary α-bromo esters by 2-propanol and 2-methyldioxolane has been shown to be a kinetically viable process with average chain lengths of >10 at temperatures between 30 and 60 deg C.For electron-deficient bromides, these simple organic reagents may effectively replace the more commonly used (and more expensive) organosilicon or tin hydrides.Some mechanistic insights have been obtained from a combination of kinetic and thermodynamic measurements.The rate constants for the reaction of the 2-hydroxy-2-propyl and the 2-methyl-1,3-dioxolan-2-yl radicals with a primary bromo ester have been estimated to be 8E3 M-1s-1 and 6E3 M-1s-1, respectively, at 30 deg C in acetonitrile.The electrochemical oxidation potentials of a number of electron-rich radicals derived from hydrogen atom abstraction from alcohols and dioxolanes, determined using photomodulation voltammetry, provide an assessment of the thermochemistry of the putative outer sphere electron-transfer reaction between the radical and the α-bromo ester (the value for 1,3-dioxolane has been redetermined and corrects an erroneous value previously published).From these data, it is shown that the order of reactivity of the organic reducing agents follows the same trend as the oxidation potentials of the corresponding radicals.Rate constants for the outer sphere electron-transfer reduction of the bromo esters by electrochemically generated radical anions were used to establish a Marcus-type relationship between the rate constants and the standard potential of the reducing agent.Comparison of these rate constants with those for the reactions of the electron-rich radicals suggest that the reactions of the methanol- and ethanol-derived radicals do not proceed via outer sphere electron transfer as had been previously suggested but have significant bonding (i.e., atom transfer) character at the transition state.Electron transfer in the reactions of the 2-propanol-, and 2-methyl-1,3-dioxolane-derived radicals cannot be rulled out.Nevertheless, the order of reactivity of the organic reducing agents follows the same trend as the oxidation potentials of the corresponding radicals suggesting that these potentials can be used as a predictive tool for the design of new reagents.
- Fontana, Francesca,Kolt, Ralph J.,Huang, Youqin,Wayner, Danial D. M.
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p. 4671 - 4676
(2007/10/02)
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- A NEW GENERAL METHOD FOR THE PREPARATION OF CARBOXYLIC ACID ESTERS
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Esters can be generated directly in good yields under mild conditions from the corresponding carboxylic acid and alcohol in the presence of equivalent amounts of pyridine, triphenylphosphine and N-halosuccinimide.Key words: Carboxylic acids, esterification, triphenylphosphine, N-halo succinimides.
- Froeyen, Paul
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p. 145 - 152
(2007/10/02)
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- Generation of esters from carboxylic acids using Appel's salt (4,5-dichloro-1,2,3-dithiazolium chloride)
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Esters can be generated directly in good yields under mild conditions from the corresponding carboxylic acid and alcohol using Appel's salt (4,5-dichloro-1,2,3-dithiazolium chloride) and 2,6-lutidine.
- Folmer,Weinreb
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p. 2737 - 2740
(2007/10/02)
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- NEW OXIDATIVE ESTERIFICATION OF ALCOHOLS WITH ALDEHYDES BY THE Br2-HMPT-NaHCO3.
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A new aldehyde-mediated oxidative esterification using a bromine/HMPT complex in the presence of sodium hydrogen carbonate is described.
- Al Neirabeyeh, Mamdouh,Pujol, M. Dolors
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p. 2273 - 2276
(2007/10/02)
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- INTERMOLECULAR DEHYDRATION BETWEEN CARBOXYLIC ACIDS AND ALCOHOLS BY THE USE OF DIETHYL AZODICARBOXYLATE AND 3-METHYLBENZOTHIAZOLE-2-SELONE
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The reaction of carboxylic acids with alcohols in the presence of diethyl azodicarboxylate and 3-methylbenzothiazole-2-selone gave the corresponding esters with retention of configuration at the alcoholic carbon atom.
- Mitsunobu, Oyo,Takemasa, Akira,Endo, Ryosuke
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p. 855 - 858
(2007/10/02)
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- DIALKYL ACYLPHOSPHONATES: A NEW ACYLATING AGENT OF ALCOHOLS
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Diethyl benzoylphosphonate (1) underwent facile benzoylation of alcohols in the presence of DBU.Reactions of diols containing primary and secondary hydroxyl groups with 1 gave predominantly monobenzoates in which primary hydroxyl groups were highly selectively benzoylated.Related acylations were also described.
- Sekine, Mitsuo,Kume, Akiko,Hata, Tsujiaki
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p. 3617 - 3620
(2007/10/02)
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