Acetylating Reagent Research Articles

Green acetylation of solketal and glycerol formal by heterogeneous acid catalysts to form a biodiesel fuel additive.

A glut of glycerol has formed from the increased production of biodiesel, with the potential to integrate the supply chain by using glycerol additives to improve biodiesel properties. Acetylated acetals show interesting cold flow and viscosity effects. Herein, a solventless heterogeneously catalyzed process for the acetylation of both solketal and glycerol formal to new products is demonstrated. The process is optimized by studying the effect of acetylating reagent (acetic acid and acetic anhydride), reagent molar ratios, and a variety of commercial solid acid catalysts (Amberlyst-15, zeolite Beta, K-10 Montmorillonite, and niobium phosphate) on the conversion and selectivities. High conversions (72-95%) and selectivities (86-99%) to the desired products results from using acetic anhydride as the acetylation reagent and a 1:1 molar ratio with all catalysts. Overall, there is a complex interplay between the solid catalyst, reagent ratio, and acetylating agent on the conversion, selectivities, and byproducts formed. The variations are discussed and explained in terms of reactivity, thermodynamics, and reaction mechanisms. An alternative and efficient approach to the formation of 100% triacetin involves the ring-opening, acid-catalyzed acetylation from solketal or glycerol formal with excesses of acetic anhydride.

ChemInform Abstract: In situ Generated Ph3P(OAc)2 as a Novel Reagent for the Efficient Acetylation of Alcohols and Thiols at Room Temperature.

AbstractThe title reagent is generated in situ in the presence of NBS or Br2.

Rapid high‐yield N‐acylation of aminothiols: N‐acetylglutathione and N‐acetylhomocysteine and their thiol pKa values

Methodology for the rapid N-acylation of aminothiols in aqueous solution using procedures commonly employed in biochemical studies is described here. Glutathione disulfide (GSSG) and homocystine were diN-acetylated in ~100% yield in 0.1 M aqueous NaHCO3 (pH 8.5) at room temperature by 2.5 equiv of the activated ester, N-hydroxysulfosuccinimidyl acetate, an efficient water-soluble acetylating reagent. Following acetone precipitation, diN-acetylGSSG was further purified and desalted on a strong anion-exchange (SAX) cartridge. DiN-acetylhomocystine was simultaneously purified and desalted on a C18 cartridge. The N-acetylated aminothiols were generated using gel-immobilized tris(2-carboxyethyl)phosphine as a reductant, which obviated the need for further purification. Alternatively, disulfide exchange with dissolved dithiothreitol yielded N-acetylglutathione, which was purified on the SAX cartridge. pH titrations of N-acetylglutathione (8.99) and N-acetylhomocysteine (9.66) as well as those of commercially available N-acetylcysteine (9.53) and N-acetylpenicillamine (10.21) yielded pK(a) (SH) values of importance for biological studies.

In situ generated Ph3P(OAc)2 as a novel reagent for the efficient acetylation of alcohols and thiols at room temperature

Ph3P, Br2, and ammonium acetate are used for the in situ generation of Ph3P(OAc)2, which was characterized by different NMR techniques. The Ph3P(OAc)2 generated was used as a novel and efficient reagent for the acetylation of alcohols and thiols in acetonitrile at room temperature under homogeneous conditions. This reaction was also performed under heterogeneous conditions using 1,3,2,4-diazadiphosphetidine as an easily prepared, stable, and heterogeneous P(III) compound.

N-Heterocyclic carbene (NHC) catalyzed chemoselective acylation of alcohols in the presence of amines with various acylating reagents

This edge article reports the synthesis and full characterization including X-ray analysis of three different acylazolium ions. The reactivity of these acylazolium ions as acylating reagents of amines and alcohols is discussed. Whereas benzylamine slowly reacts with the acylazolium ions, benzyl alcohol acylation does not occur. However, upon activation of the alcohol with an N-heterocyclic carbene (NHC) as catalyst, efficient esterification is achieved. Importantly, benzylester formation is obtained in the presence of benzylamine upon selective alcohol activation by the NHC. High level DFT calculations reveal that alcohol activation occurs by strong H-bond formation between the NHC and the alcohol thereby increasing the nucleophilicity of the alcohol. For oxidatively generated acylazolium ions under NHC catalysis, the carbene has a dual role (cooperative catalysis): (a) the NHC is used for generation of the acylazolium ion and (b) the NHC is used for activation of the alcohol in the subsequent acylation step. NHC-catalyzed selective acylation of benzyl alcohol in the presence of benzylamine can also be achieved with trifluoroethyl and hexafluoroisopropylesters as acylation reagents. Moreover, an enol acetate also shows high O-selectivity as a chemoselective acetylation reagent. Kinetic and mechanistic studies are provided and some examples of the chemoselective acylation of amino alcohols are presented.

Calcyon Forms a Novel Ternary Complex with Dopamine D1 Receptor through PSD-95 Protein and Plays a Role in Dopamine Receptor Internalization

Calcyon, once known for interacting directly with the dopamine D(1) receptor (D(1)DR), is implicated in various neuropsychiatric disorders including schizophrenia, bipolar disorder, and attention deficit hyperactivity disorder. Although its direct interaction with D(1)DR has been shown to be misinterpreted, it still plays important roles in D(1)DR signaling. Here, we found that calcyon interacts with the PSD-95 and subsequently forms a ternary complex with D(1)DR through PSD-95. Calcyon is phosphorylated on Ser-169 by the PKC activator phorbol 12-myristate 13-acetate or by the D(1)DR agonist SKF-81297, and its phosphorylation increases its association with PSD-95 and recruitment to the cell surface. Interestingly, the internalization of D(1)DR at the cell surface was enhanced by phorbol 12-myristate 13-acetate and SKF-81297 in the presence of calcyon, but not in the presence of its S169A phospho-deficient mutant, suggesting that the phosphorylation of calcyon and the internalization of the surface D(1)DR are tightly correlated. Our results suggest that calcyon regulates D(1)DR trafficking by forming a ternary complex with D(1)DR through PSD-95 and thus possibly linking glutamatergic and dopamine receptor signalings. This also raises the possibility that a novel ternary complex could represent a potential therapeutic target for the modulation of related neuropsychiatric disorders.

New mixed ligand coated platinum nanoparticles for heterogeneous catalytic applications

A series of platinum nanoparticles was prepared for the first time in presence of one hydrophobic ligand and one hydrophilic ligand containing terminal sulfonic acid headgroup. This mixed ligand combination causes stripe-like domains circumscribing the nanoparticles, thereby enhancing the catalytic efficiency compared to single ligand coated Pt nanocatalysts. This could be achieved by strategically replacing the hydrophilic ligand (3-mercaptopropane-1-sulfonic acid or MPSA) with hydrophobic ligands (linear alkanethiols like 1-octanethiol or OT) on the surface of the nanoparticles. Apart from the ligand composition, the metallic core of the nanocomposite also influences the catalytic efficiency of the ligand shell through a synergistic effect. Herein we report the effects of ligand shell composition and structure on the efficiency of the nanocomposites on catalytic acylation reactions. Quite high conversion of benzyl alcohol to benzyl acetate (with >99% selectivity) was observed when acetic acid was used as the acetylating reagent and MPSA–OT–Pt as nanocatalyst at 80°C. The turnover frequency of reaction using MPSA–OT–Pt nanocatalyst was found to be an order of magnitude higher than that using well known solid acid catalyst zeolite USY under identical reaction conditions. Further, the selectivity toward benzyl acetate using USY was ≤80%, the remaining 20% being dibenzylether. It was also found that the MPSA–OT–Pt nanocatalyst system shows higher activity than gold nanoparticles coated with same set of ligands (such as MPSA–OT–Au nanocatalyst). Additionally, the effects of changing the substrate (such as 1-butanol) and the acylating agent (such as propionic acid) were also studied.

Acetylation of alkali-treated peat

The effects of time, temperature, and the amount of an acetylating reagent in the esterification of peat with acetic anhydride in the presence of sodium hydroxide after mechanochemical activation on the concentration of bound acetyl groups and the solubility of the resulting products in acetone were studied.

Isopropenyl acetate, a remarkable, cheap and acylating agent of amines under solvent- and catalyst-free conditions: a systematic investigation

Isopropenyl acetate was proved to be an efficient reagent for acetylation of amine in the absence of solvent and catalyst. The corresponding acetamides were obtained in very high yields without any purification.

Synthesis of glucose esters from cellulose in ionic liquids

Abstract The transformation of cellulose into glucose ester α-d-glucose pentaacetate (GPAc) was carried out in ionic liquid 1-butyl-3-methylimidazolium chloride under mild reaction conditions. The reaction comprises two steps: the first involves a hydrolysis reaction, yielding α-d-glucose and glucose oligomers; and then only after some time, the acetylating reagent acetic anhydride is added. Under optimized conditions and with the acidic resin Amberlyst 15DRY as a hydrolysis catalyst, a 70% yield of GPAc was obtained. This product could be quantitatively isolated by simple liquid-liquid extraction, which allowed easy recycling of the ionic liquid and catalyst.

Lipase catalyzed resolution of trans-11,12-bis(hydroxymethyl)-9,10-dihydro-9,10-ethanoanthracene: facile access to both enantiomers and the synthesis of their amino derivatives

The lipase mediated resolution of roof shaped trans-11,12-bis(hydroxymethyl)-9,10-dihydro-9,10-ethanoanthracene using vinyl acetate as an acetylating reagent is achieved. This method gives easy access to both enantiomers of the molecule in very high enantiomeric purity. The chiral diol is converted to diamino and aminoalcohol derivatives by simple chemical transformations.

Mapping Surface Accessibility of the C1r/C1s Tetramer by Chemical Modification and Mass Spectrometry Provides New Insights into Assembly of the Human C1 Complex

C1, the complex that triggers the classic pathway of complement, is a 790-kDa assembly resulting from association of a recognition protein C1q with a Ca(2+)-dependent tetramer comprising two copies of the proteases C1r and C1s. Early structural investigations have shown that the extended C1s-C1r-C1r-C1s tetramer folds into a compact conformation in C1. Recent site-directed mutagenesis studies have identified the C1q-binding sites in C1r and C1s and led to a three-dimensional model of the C1 complex (Bally, I., Rossi, V., Lunardi, T., Thielens, N. M., Gaboriaud, C., and Arlaud, G. J. (2009) J. Biol. Chem. 284, 19340-19348). In this study, we have used a mass spectrometry-based strategy involving a label-free semi-quantitative analysis of protein samples to gain new structural insights into C1 assembly. Using a stable chemical modification, we have compared the accessibility of the lysine residues in the isolated tetramer and in C1. The labeling data account for 51 of the 73 lysine residues of C1r and C1s. They strongly support the hypothesis that both C1s CUB(1)-EGF-CUB(2) interaction domains, which are distant in the free tetramer, associate with each other in the C1 complex. This analysis also provides the first experimental evidence that, in the proenzyme form of C1, the C1s serine protease domain is partly positioned inside the C1q cone and yields precise information about its orientation in the complex. These results provide further structural insights into the architecture of the C1 complex, allowing significant improvement of our current C1 model.

Quantification of free and total bisphenol A and bisphenol B in human urine by dispersive liquid–liquid microextraction (DLLME) and heart-cutting multidimensional gas chromatography–mass spectrometry (MD–GC/MS)

A novel method combining dispersive liquid–liquid microextraction (DLLME) and heart-cutting multidimensional gas chromatography coupled to mass spectrometry was developed for the determination of free and total bisphenol A (BPA) and bisphenol B (BPB) in human urine samples. The DLLME procedure combines extraction, derivatization and concentration of the analytes into one step. Several important variables influencing the extraction efficiency and selectivity such as nature and volume of extractive and dispersive solvents as well as the amount of acetylating reagent were investigated. The temperature and time to hydrolyze BPA and BPB conjugates with a β-glucuronidase and sulfatase enzyme preparation were also studied. Under the optimized conditions good efficiency extraction (71–93%) and acceptable total DLLME yields (56–77%) were obtained for both analytes. Matrix-matched calibration curves were linear with correlation coefficients higher than 0.996 in the range level 0.1–5 μg/l, and the relative standard deviations (%RSD) were lower than 20% ( n = 6). The limits of detection were 0.03 and 0.05 μg/l for BPA and BPB, respectively. The applicability of the proposed method for determining urinary free and total BPA and BPB was assessed by analyzing the human urine of a group of 20 volunteers. Free BPA was detected in 45% of the sample whereas total BPA was detected in 85% of the samples at concentrations ranging between 0.39 and 4.99 μg/l. BPB was detected in conjugated form in two samples.

Acetylation reaction of polytetramethylene glycol with acetic anhydride in pyridine

AbstractThe acetylation reaction of polytetramethylene glycol (PTMG) with acetic anhydride in pyridine was studied. The extent of acetylation was measured by 1H‐NMR, and the acetylation product was characterized with FTIR, 1H‐NMR, and 13C‐NMR. The effects of the experimental conditions, i.e., reaction time and temperature, acetylation reagent concentration (anhydride and hydroxyl molar ratio), were investigated. The increase in reaction temperature and reaction time favored the acetylation yields. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1138–1142, 2007

Pasting properties and (chemical) fine structure of acetylated yellow pea starch is affected by acetylation reagent type and granule size

Yellow pea starch was fractionated into small and large size granule fractions and then modified with acetic anhydride and vinyl acetate (acetylation after sieving) or first acetylated in the same way and then fractionated into small and large size fractions (acetylation before sieving). Acetylation with different procedures (acetylation before or after sieving) resulted in different degrees of substitution for small size granule fractions when acetic anhydride was used as reagent. Modification with vinyl acetate gave products with much higher peak viscosities than modification with acetic anhydride for the same granule size and same degree of substitution (DS). The location and distribution of acetyl groups was investigated by analyzing the α-amylase hydrolysates of isolated amylose and amylopectin with chromatography and mass spectrometry. Mass spectra showed that the substituent distribution mainly depended on the type of reagent and was not affected by the granule size. Both amylose and amylopectin were modified in an heterogeneous way and the reactions took place in different regions of the granule. It is postulated that acetylation occurs more homogeneously throughout the granule when vinyl acetate is used as reagent, while the reaction with acetic anhydride to a large extent takes place in the outer lamellae of granule.

Bis(cyclopentadienyl) zirconium dichloride catalyzed acetylation of phenols, alcohols and amines

Cp 2ZrCl 2 catalyst is used for the acetylation of structurally diverse phenols, alcohols and amines with acetic anhydride as an acetylating reagent under solvent free conditions.

Silphos [PCl3‐n(SiO2)n]: A Heterogeneous Phosphine Reagent for Formylation and Acetylation of Alcohols and Amines with Ethyl Formate and Acetate.

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N,N-Dibromo-4-methylbenzenesulphonimide as economical reagent for facile and selective catalyzed acetylation of alcohols under mild conditions

N,N-Dibromo-4-methylbenzenesulphonimide efficiently catalyzes acylation of structurally diverse alcohols by the action of acetic anhydride in chloroform at room temperature.

Silphos [PCl 3− n(SiO 2) n]: a heterogeneous phosphine reagent for formylation and acetylation of alcohols and amines with ethyl formate and acetate

Alcohols and amines are formylated and acetylated in the presence of Silphos [PCl 3− n (SiO 2) n ] in ethyl formate and ethyl acetate in high to excellent yields. This procedure provides a method to separate the product by a simple filtration.

Evaluation of TCS/ZnCl2 with Acetic Anhydride as an Acetylating Reagent for Methylene Ketones.

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