- Chemoselective: O -formyl and O -acyl protection of alkanolamines, phenoxyethanols and alcohols catalyzed by nickel(ii) and copper(ii)-catalysts
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Achieving chemoselectivity is always crucial and challenging for bi-functional compounds, such as alkanolamines, that have both amines and alcohols as reactive functional groups. Achieving 100% selectivity for O-formyl and O-acyl protection of alkanolamines is one of the examples of such reactions. To avoid protection and deprotection steps and overcome this problem, a novel chemoselective, efficient, and simple protocol for functional group protection as O-formylation and O-acylation of alkanolamines and phenoxyethanols and competitive O-selectivity between alcohols and amines, catalyzed by Ni(ii) and Cu(ii) complexes with 8-hydroxyquinoline at a catalyst loading of only 5 mol% in a homogeneous medium has been presented here. Good to excellent yields are achieved in the absence of a solvent for O-formylation at room temperature with formic acid as the formyl source and O-acylation at 70 °C with acetic acid as the acyl source. In addition, minimal effluent and waste are generated during this reaction, as the corresponding sodium salts of acids could be recovered during the process and can be reused. This chemistry readily tolerates a variety of functional groups, as demonstrated by 20 examples with 100% chemoselectivity for O-formylation and O-acylation of alkanolamines and 30 examples of O-formylation and O-acylation of phenoxyethanols and alcohols in the presence of amines which have been synthesized successfully.
- Sonawane, Rahul B.,Sonawane, Swapnali R.,Rasal, Nishant K.,Jagtap, Sangeeta V.
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supporting information
p. 3186 - 3195
(2020/06/19)
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- KMnO4-catalyzed chemoselective deprotection of acetate and controllable deacetylation-oxidation in one pot
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A novel and efficient protocol for chemoselective deacetylation under ambient conditions was developed using catalytic KMnO4. The stoichiometric use of KMnO4 highlighted the dual role of a heterogeneous oxidant enabling direct access to aromatic aldehydes in one-pot sequential deacetylation-oxidation. The reaction employed an alternative solvent system and allowed the clean transformation of benzyl acetate to sensitive aldehyde in a single step while preventing over-oxidation to acids. Use of inexpensive and readily accessible KMnO4 as an environmentally benign reagent and the ease of the reaction operation were particularly attractive, and enabled the controlled oxidation and facile cleavage of acetate in a preceding step. This journal is
- Gurawa, Aakanksha,Kumar, Manoj,Rao, Dodla S.,Kashyap, Sudhir
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supporting information
p. 16702 - 16707
(2020/10/27)
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- Preparation of acetates catalyzed by boric acid and/or tungstophosphoric acid-modified zirconia obtained employing polyethylene glycols as pore-forming agents
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Zirconia modified with boric acid and/or tungstophosphoric acid calcined at 320 °C were prepared, characterized and used as catalysts in the production of acetates from diverse alcohols and phenols. Polyethylene glycol (PEG) of different molecular weight (400, 2000, 6000 Da) were added as low cost pore-forming agents during zirconia synthesis using zirconyl chloride as precursor and ammonium hydroxide as precipitating agent. The zirconias were impregnated with aqueous solutions of boric acid and/or tungstophosphoric acid (TPA). The borated zirconias, zirconias modified with TPA and zirconias doped with both boron and TPA were amorphous mesoporous materials with very strong acid sites, and specific surface areas SBET of around 200, 100, and 150 m2/g, respectively. The FT-IR spectra of borated zirconias exhibited the bands of boron species, while the zirconias modified with TPA presented the characteristic bands of tungstophosphate anion, and the zirconias doped with both boron and TPA showed a degradation of the TPA anion, confirmed by 31P MAS-NMR. The borated zirconias and the zirconias modified with TPA gave excellent selectivity and yield in the 2-phenylethanol esterification with acetic acid. The use of these materials allows obtaining higher or similar results than those reported in the literature. Zirconias doped with both boron and TPA gave lower values, due to the transformation of the [PW12O40]3? Keggin anion in to the [P2W21O71]6? and [PW11O39]7? species. The reactivity towards acetylation with acetic acid of different alcohols and phenols using the best catalyst was ordered according to: primary alcohols > secondary alcohols > phenols. The reactivity difference of the alcohols and phenols was correlated with the electronic density on the oxygen atom and steric effects.
- Osiglio, Lilian,Sathicq, Gabriel,Pizzio, Luis,Romanelli, Gustavo,Blanco, Mirta
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- Efficient and selective N-, S- and O-acetylation in TEAA ionic liquid as green solvent. Applications in synthetic carbohydrate chemistry
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Background: The ionic liquid triethylammonium acetate (TEAA) was found to be an efficient solvent in the acetylation of alcohols, amines, oximes and thiols to their corresponding acetyl compounds using only a 10% excess of acetic anhydride under mild conditions. Moreover TEAA is not only an inexpensive and recyclable solvent but also an anomeric selective catalyst in the per-O-acetylation of sugar moieties. Methods: Simple and effective organic synthesis protocols were provided for the selective acetylation of several substrates. The products were fully characterized by 1H and 13C NMR spectroscopy and the anomeric ratios were obtained from the 1H spectra. Results: Structurally diverse alcohols, phenols, thiols, amines, carbohydrates and oximes underwent acylation under mild conditions by this procedure to provide the corresponding acetates in excellent yields. TEAA ionic liquid is unique in its capability to act as both, solvent and high selective catalyst. As expected, the reaction proceeds with high b anomeric selectivity for sugars derivatives. Moreover, the ionic liquid was regenerated, recycled and reused for three times without apparent loss of reactivity and selectivity in all cases. Conclusions: The present procedure provides a powerful and versatile acylation method for alcohols, phenols, thiols, amines, oximes and carbohydrates. This protocol is endowed with several unique merits: selectivity, cost-efficiency, atom-economy and mild reaction conditions tolerable to acid sensitive functionalities. With these features, this method may be considered as a better alternative for the acetylation of a wide range of substrates.
- Lafuente, Leticia,Díaz, Gisela,Bravo, Rodolfo,Ponzinibbio, Agustín
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p. 195 - 200
(2016/02/26)
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- A method for esterification reaction rate prediction of aliphatic monocarboxylic acids with primary alcohols in 1,4-dioxane based on two parametrical taft equation
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Esterification reaction rates of aliphatic monocarboxylic acids with primary alcohols in 1,4-dioxane as inert solvent were investigated. Acids were esterified with 1-propanol and alcohols with acetic acid as model reactants at a constant temperature of 60°C, at a fixed ionic strength and pH in a batch reactor with a constant volume. For evaluation of reaction rates, an exact kinetic equation for the equilibrium reaction was applied. Under these conditions and for low reactants, concentrations reaction rate depends only on the structure of reactants and, therefore, can be predicted by a correlation equation with two Taft coefficients (inductive and steric effects). From these equations, it is possible to estimate the esterification reaction rate constant for other acid-alcohol pairs. This methodology may also be suitable for other kinetic systems measured under comparable experimental conditions.
- Vojtko, Jan,Tomcik, Peter
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p. 189 - 196
(2014/02/14)
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- Borated zirconia modified with ammonium metatungstate as catalyst in alcohol acetylation
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Samples of tungsten-modified borated zirconia were prepared to be used as catalyst in 2-phenoxyethanol acetylation. The borated zirconias were obtained by impregnation of two zirconias (S2 and S4) obtained by the micellar method using different zirconium precursor concentrations with boric acid solution containing 0.3 moles B/dm3. These solids and the parent zirconias were impregnated with two concentration levels of ammonium metatungstate solutions (0.11 and 0.22 moles W/dm3). The solids containing boron mainly have amorphous characteristics and strong acidity, while those that contain only tungsten showed stronger acidity and evidence of the presence of a crystalline phase. The specific surface area and the pore volume slightly decreased in the solids obtained by adding tungsten to borated zirconia, and more markedly in those that contain only tungsten, and the mean pore size increased with respect to the parent support. It was observed that in the 2-phenoxyethanol acetylation using acetic acid as acylating agent and tungsten-modified borated zirconia as catalyst, the yield to acetylated product was high and it is correlated with the acid strength of the catalysts. In turn, the solids that contain only tungsten have a correlation with the acidity, but lead to low yield values due to a poorer dispersion of the tungsten species. The best yield was obtained with the catalyst prepared with the borated S4 zirconia containing 15% g B2O3/100 g support and 12.5% g W/100 g support. Using this catalyst and the same reaction conditions, the acetylation of different alcohols and phenols was studied, the reactivity order being as follows: primary alcohols > secondary alcohols > phenols.
- Osiglio, Lilian,Sathicq, ángel G.,Romanelli, Gustavo P.,Blanco, Mirta N.
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experimental part
p. 97 - 103
(2012/07/14)
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- Investigation of steapsin lipase for kinetic resolution of secondary alcohols and synthesis of valuable acetates in non-aqueous reaction medium
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In present study, the application of steapsin lipase (as a biocatalyst) was investigated for kinetic resolution of secondary alcohols (1-phenyl ethanol and their derivatives) using vinyl acetate as an activated acyl donor. The enzymatic protocol was optimized for various reaction parameters such as effect of the molar ratio, solvent, temperature, time and biocatalyst loading to obtain best reaction conditions. On optimization, developed enzymatic methodology provided considerable enantiomeric excess of the product (up to 92% ee) at 55 °C in n-hexane as a solvent. Furthermore using the developed protocol, synthesis of several industrially important acetates was successfully achieved with excellent yield (up to 99%). During acetate synthesis, the biocatalyst was remarkably reused for eight consecutive recycles without any significant loss in its catalytic activity. This revealed the good potential of steapsin lipase for application in organic solvents.
- Dhake, Kishor P.,Deshmukh, Krishna M.,Wagh, Yogesh S.,Singhal, Rekha S.,Bhanage, Bhalchandra M.
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experimental part
p. 15 - 23
(2012/06/29)
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- PHOTOCHROMIC MATERIALS THAT INCLUDE 6-AMINO SUBSTITUTED INDENO-FUSED NAPHTHOPYRANS
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The present invention relates to photochromic materials that include certain indeno-fused naphthopyrans. The indeno-fused naphthopyrans have an amino group (e.g., a piperidino or morpholino group) bonded to the 6-position and an optional halo group (e.g.,
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Page/Page column 18
(2012/03/12)
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- Significant heterogeneous carbonate salt catalyzed acetylation of alcohols via a transesterification process with carbonate salt-activated alcohol 1H NMR evidence
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Heterogeneous carbonate salt catalyzed acetylation of alcohols via a transesterification process has been developed. Various esters are furnished up to 97% yield. Established procedure is simple and air-tolerant with readily available reagents. Ethyl acetate and isobutyl acetate are used as not only acetylating agents, but also reaction solvents in transesterification. Aliphatic linear alcohols, allylic alcohols and benzyl alcohols show high reactivities in the presence of 1 or 5 mol% Cs2CO3 at 125°C. Cesium carbonate can be recycled by pumping liquid phase out of reactor after reaction. During four cycle runs for reaction of 2-phenylethanol and ethyl acetate, high yields of phenethyl acetate are provided (>60% yield). Based on experiments and 1H NMR investigation, bifunctional catalysis is proposed, alcohol activated by carbonate ion is confirmed, and higher activity of catalytic amount than stoichiometric cesium carbonate is interpreted. Copyright
- Xiong, Yan,Zhang, Xueqiang
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experimental part
p. 1143 - 1148
(2012/03/26)
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- Alcohol acetylation with acetic acid using borated zirconia as catalyst
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The use of zirconium oxide doped with boron (borated zirconia) as catalyst in the acetylation of alcohols and phenol was studied. The catalysts were obtained by employing different preparation conditions, in order to observe the effect of the concentration of the precursor in the solution used to obtain the oxide, the concentration of the boron precursor, and the calcination temperature. All the solids showed amorphous characteristics and strong acidity. Boron addition increased the temperature range of the hydrated oxide stability, which depends on the boron concentration in the sample. Besides, the characterization by infrared spectroscopy showed an effect on the boron species present in the solid depending on the added concentration. The three preparation conditions under study affected the textural properties of the catalysts, as well as their acid strength. It was observed that in the acylation of alcohols using acetic acid as acylating agent and toluene as reaction solvent, at reflux temperature, the yield of acetylated product correlated with the acid strength of the catalysts, which depended on the preparation conditions. The best yield was achieved with a catalyst obtained using a high solution concentration of the oxide precursor (0.56 mmoles Zr/cm3), an intermediate boron concentration (15 g B2O3/100 g support) and a relatively low calcination temperature (320 °C).
- Osiglio, Lilian,Romanelli, Gustavo,Blanco, Mirta
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experimental part
p. 52 - 58
(2010/05/01)
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- Keratinocyte growth inhibitors and hydroxamic acid derivatives
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This invention relates to a keratinocyte-proliferation inhibitor comprising as active ingredient a compound having an activity of inhibiting the solubilization of heparin-binding EGF-like growth factor bound to cell membranes and a compound of the formula (I); or pharmaceutically acceptable salt thereof, wherein R1, R2, R3 are hydrogen atom or alkyl and X is substituted benzene or the like.
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- Ionic liquids as reaction media for esterification of carboxylate sodium salts with alkyl halides
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Ionic liquids based on 1,3-dialkylimidazolinium methanesulfonate have been used as effective reusable reaction media in the esterification of several carboxylate sodium salts with different alkyl halides. Products are easily isolated by extraction with ether, and the protocol is mild and green, compared to the existing methods based on toxic solvents. Proper 'design' of the ionic liquid allows us to obtain esters always in quantitative yields.
- Brinchi,Germani,Savelli
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p. 2027 - 2029
(2007/10/03)
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- One-step conversion of silyl/THP ethers into the corresponding acetates
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A variety of silyl and THP ethers were directly converted into the corresponding acetates using acetic anhydride in the presence of a catalytic amount of Cu(OTf)2 in CH2Cl2. It was observed that MEM ethers could also be cl
- Chandra, Kusum L,Saravanan, P,Singh, Vinod K
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p. 5309 - 5311
(2007/10/03)
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- Synthesis of indole, benzofuran and benzothiophene by pyrolysis of 2-anilinoethanol, 2-phenoxyethanol and 2-(phenylthio)ethanol acetates
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The synthesis of indole is possible by pyrolysis of compounds of the general formula : ΦNHCH2CH2X. The pyrolysis of the acetates (X = OCOCH3) of 2-anilinoethanol 3a, 2-phenoxyethanol 3b and 2-(phenylthio)ethanol 3c was studied by surface response methodology. A possible mechanism involving a radical pathway is discussed in terms of bond dissociation energies, thermal stability of the pyrolysis products and configuration of the radical intermediates. Elsevier,.
- Afxantidis, Jean,Aune, Jean-Pierre
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p. 395 - 403
(2007/10/03)
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- Reaction of Hemiacetal Esters, Acetals, and Acylals with Alcohols or Acetic Acid
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Hemiacetal esters undergo rapid exchange with alcohols at room temperature to give mixtures of hemiacetal ester and acetal.The equilibration requires acid catalysis, and equilibrium lies far in favor of the acetal (>95percent).Acetals undergo exchange with carboxylic acids to give the same equilibrium mixtures as that achieved by using the corresponding hemiacetal ester and alcohol.The use of a large excess of carboxylic acid can convert acetals to hemiacetal esters.Under more vigorous conditions, both acetals and hemiacetal esters react with acetic acid to form acetates.The reaction of hemiacetal esters or acetals with anhydrous hydrogen chloride yields α-chloro ethers.The thermolysis of hemiacetal esters is also examined.Acylals do not undergo substitution as observed for acetals and hemiacetal esters.The reaction of acylals with alcohols results in ester formation with no exchange.Under acid conditions, hemiacetal esters are more reactive than either acetals or acylals.
- Gallucci, R. R.,Going, R. C.
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p. 3517 - 3521
(2007/10/02)
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