Acetylating Reagent Research Articles

Preparation, characteristics and antioxidant activity of mung bean peel polysaccharides

The mung bean peel polysaccharide (MBP) extracted by hot water was chemically modified. By changing the dosage of phosphorylation reagent and acetylation reagent, three kinds of phosphorylated MBP ( P-MBP-1, P-MBP-2, P-MBP-3 ) and acetylated MBP ( AC 0.6-MBP, AC 1-MBP, AC 1.4-MBP ) with different degrees of substitution were prepared. By measuring the sugar content and substitution degree of the modified products, it was found that the amount of reagent had a certain effect on both of them. The modified products were determined by infrared spectrum and nuclear magnetic resonance. The results showed that the chemical modification was successful. The in vitro antioxidant capacity (·OH scavenging ability, O2−·clearing ability, reducing capacity, resistance to lipid peroxidation) of seven polysaccharide were measured, which manifested that chemical modification could enhance the antioxidant ability of MBP to varying degrees, and the DS also had a certain impact on their antioxidant activity. This promoted the development of mung bean peel polysaccharide functional products and the utilization of mung bean peel resources.

Site-specific acetyl modification of 2'-OH of RNA by an oligonucleotide acetylating reagent.

The method for a site-specific RNA acetylation using a novel oligonucleotide acetylating probe (Ac-probe) has been developed. It was confirmed that the acetyl group was site-specifically introduced to a 2'-OH of the sugar part of the target RNA via the formation of the RNA-probe duplex.

Photocatalytic sequential C-H functionalization expediting acetoxymalonylation of imidazo heterocycles.

The importance of functionalized imidazo heterocycles has often been featured in several impactful research both from academia and industry. Herein, we report a direct C-3 acetoxymalonylation of imidazo heterocycles using relay C-H functionalization enabled by organophotocatalysis starring zinc acetate in the triple role of an activator, ion scavenger as well as an acetylating reagent. The mechanistic investigation revealed a sequential sp2 and sp3 C-H activation, followed by functionalization driven by zinc acetate coupled with the photocatalyst PTH. A variety of imidazo[1,2-a]pyridines and related heterocycles were explored as substrates along with several active methylene reagents, all generating the products with excellent yields and regioselectivity, thus confirming excellent functional group tolerability.

Photoinduced Acetylation of Anilines under Aqueous and Catalyst-Free Conditions

A green and efficient visible-light induced functionalization of anilines under mild conditions has been reported. Utilizing nontoxic, cost-effective, and water-soluble diacetyl as photosensitizer and acetylating reagent, and water as the solvent, a variety of anilines were converted into the corresponding aryl ketones, iodides, and bromides. With advantages of environmentally friendly conditions, simple operation, broad substrate scope, and functional group tolerance, this reaction represents a valuable method in organic synthesis.

Vinylene carbonate: beyond the ethyne surrogate in rhodium-catalyzed annulation with amidines toward 4-methylquinazolines.

In this paper, we developed a rhodium-catalyzed annulation of vinylene carbonate with amidines, leading to 4-methylquinazolines with moderate to excellent yields. This procedure proceeded by sequential ortho-acylation and annulation, where vinylene carbonate served as the acetylation reagent rather than the ethyne surrogate.

Electron ionization induced fragmentation of fluorinated derivatives of bisphenols.

Fluorinated derivatization agents allow for the identification and quantification of emerging pollutants with high sensitivity, yet details of their potential applications using electron ionization are lacking. The fluorine atom itself does not effectively participate in electron ionization. Furthermore, limited information exists regarding the effect of fluorine during electron ionization-induced fragmentation. To fill this gap, this report presents the fragmentation pathways of the fluorinated derivatives of ten bisphenol analogues as exemplary emerging pollutants. The bisphenols were derivatized by the acetylation reagent trifluoroacetic anhydride and a new silylation reagent, namely dimethyl(3,3,3-trifluoropropyl)silyldiethylamine (DIMETRIS; previously applied for the analysis of selected pharmaceuticals in environmental samples), and analyzed using GC/MS (electron ionization, 70 eV). Deuterated bisphenol A was added to the group of analytes to confirm the proposed fragmentation pathways. The specific chemical structure of bisphenols gives the possibility of several resonance hybrids of C-centered radicals. This, in turn, results in several fragmentation pathways, unique for each resonance hybrid. Sequential losses of radicals and neutral fragments were observed in both types of derivative, with final stable carbenium ions. McLafferty-type rearrangements were observed between the native structure of the analytes and the introduced substituents. The gamma-shift of F onto Si in the Si(CH2 )2 CF3 substituent is proposed to explain the loss of the fragment with a mass of 78 u. Both types of derivatization reagent used were found to be applicable, although the use of DIMETRIS was limited for high-mass bisphenols. The introduction of fluorine by derivatization brings benefits for the qualitative and quantitative analysis of bisphenol-type compounds using GC/MS because of the presence of characteristic ions in the mass spectra.

Synthesis of task-specific imidazolium ionic liquid as an efficient catalyst in acetylation of alcohols, phenols, and amines

Herein, we report the synthesis of task-specific amino-functionalized imidazolium ionic liquid, acetate1-(2-tert-butoxycarbonylamino-ethyl)-3-methyl-3H-imidazol-1-ium; (Boc-NH-EMIM.OAc), as an efficient catalyst for the acetylation of alcohols, phenols, and amines in the presence of acetic anhydride (acetylating reagent). Remarkably, acetic anhydride in the presence of 10 mol% of catalyst (Boc-NH-EMIM.OAc) under solvent-free conditions showed excellent acetylation activity in shorter duration of time. On the basis of this, a general procedure for acetylation of alcohols, phenols, and amines has been developed. The ionic liquid (Boc-NH-EMIM.OAc) can be readily recovered and reused successfully up to four consecutive cycles without any significant loss of its catalytic activity. We have been able to show that this acetylating method has many advantages. It gives high yields, takes shorter time, and develops the possibility of benign environmental-friendly process.

Phenolic Resin Foam Composites Reinforced by Acetylated Poplar Fiber with High Mechanical Properties, Low Pulverization Ratio, and Good Thermal Insulation and Flame Retardant Performance.

Phenolic foam composites (PFs) are of substantial interest due to their uniform closed-cell structure, low thermal conductivity, and good thermal insulation performance. However, their disadvantages of a high pulverization rate and poor mechanical properties restrict their application in building exterior insulation. Therefore, the toughening of these composites is necessary. In this paper, poplar fiber was treated with an acetylation reagent, and the acetylated fiber was used to prepare modified phenolic foams (FTPFs); this successfully solved the phenomenon of the destruction of the foam structure due to the agglomeration of poplar fiber in the resin substrate. The foam composites were comprehensively evaluated via the characterization of their chemical structures, surface morphologies, mechanical properties, thermal conductivities, and flame retardant properties. It was found that the compressive strength and compressive modulus of FTPF-5% respectively increased by 28.5% and 37.9% as compared with those of PF. The pulverization ratio was reduced by 32.3%, and the thermal insulation performance and flame retardant performance (LOI) were improved. Compared with other toughening methods for phenolic foam composites, the phenolic foam composites modified with surface-compatibilized poplar fiber offer a novel strategy for the value-added utilization of woody fiber, and improve the toughness and industrial viability of phenolic foam.

Copper-Catalyzed Acetylation of Electron-Rich Phenols and Anilines

An approach has been developed for the copper-catalyzed acetylation of phenols and anilines with potassium thioacetate as an acetylating reagent. Although only electron-rich phenols and anilines are compatible with this protocol, the reaction can provide moderate to high yields under mild conditions. Compared with other acetylating reagents, the current reagent has certain advantages, such as its low cost, easy availability, stability, insensitivity to water or air, and ease of storage.

Rh(III)‐Catalyzed Regioselective Acetylation of sp2 C−H Bond Starting from Paraformaldehyde

AbstractRh(III)‐catalyzed acetylation of sp2 C−H bonds has been realized using paraformaldehyde as an acetylating reagent. This procedure features simultaneous formation of two C−C bonds, external oxidants free, and water as the sole byproducts, thus offering an environmentally benign acetylation of arenes. A range of functional groups tolerance were observed.

A magnetically recoverable copper–salen complex as a nano-catalytic system for amine protection via acetylation using thioacetic acid

A novel copper(II)–salen complex was immobilized on the surface of magnetite nanoparticles using chitosan as a linker. This system exhibits superior catalytic activity in acetyl protection of various amines with thioacetic acid as the acetylating reagent. The method has advantages over others in high selectivity, simple work-up, green reaction medium and the application of an easily recoverable heterogeneous catalyst.

Cellulose triacetate synthesis via one-pot organocatalytic transesterification and delignification of pretreated bagasse.

Cellulose triacetate was synthesised by the transesterification reaction of mild acid-pretreated lignocellulosic biomass with a stable acetylating reagent (isopropenyl acetate, IPA) in an ionic liquid (1-ethyl-3-methylimidazolium acetate, EmimOAc) which enabled the dissolution of lignocellulose as well as the organocatalytic reaction. The homogeneous acetylation of pretreated sugar-cane bagasse was carried out under mild conditions (80 °C, 30 min), and the subsequent reprecipitation processes led to enriched cellulose triacetate with a high degree of substitution (DS; 2.98) and glucose purity (∼90%) along with production of lignin acetate.

Acetylation of Microcrystalline Cellulose by Transesterification in AmimCl/DMSO Cosolvent System.

Recently, IL/cosolvent systems have generated a lot of interest as cellulose-dissolving solvents and reaction media for various kinds of cellulose modification. In the present study, both 1-allyl-3-methylimidazolium chloride (AmimCl)/dimethyl sulfoxide (DMSO) and AmimCl/N,N-dimethylformamide (DMF) systems were employed to synthesize cellulose acetate by transesterification. Microcrystalline cellulose, 1,8-diazabicyclo[5.4.0]undec-7-ene and isopropenyl acetate were chosen as the raw material, catalyst and acetylation reagent, respectively. The results revealed that DMSO was a suitable cosolvent for the transesterification in the homogeneous solution. Moreover, DMSO had a positive effect on the reaction as the cosolvent under the given conditions and the degree of the substitution of cellulose acetate could be significantly enhanced through increasing the molar ratio of DMSO. The synthesized products were characterized by Fourier transform infrared (FT-IR) spectroscopy, 1H and 13C nuclear magnetic resonance spectroscopy (1H-NMR and 13C-NMR), correlation spectroscopy (COSY), heteronuclear single quantum correlation (HSQC) spectroscopy, and X-ray diffraction (XRD) to confirm the chemical and physical structure of the cellulose acetate generated. The thermal properties were also evaluated using thermogravimetric analysis (TGA)/derivative thermogravimetry (DTG).

Characterization of Type-II Acetylated Cellulose Nanocrystals with Various Degree of Substitution and Its Compatibility in PLA Films.

In order to decrease the self-agglomeration and improve the hydrophobic properties of type-II acetylated cellulose nanocrystals (ACNC II), various degree of substitution (DS) values of ACNCs were successfully prepared by a single-step method from microcrystalline cellulose with anhydrous phosphoric acid as the solvent, and acetic anhydride as the acetylation reagent, under different reaction temperatures (20–40 °C). To thoroughly investigate the DS values of ACNC II, analyses were performed using Fourier transform infrared spectroscopy (FT-IR), 13C cross polarization-magic angle spinning (CP-MAS) nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS). At a reaction temperature of 40°C, the highest DS value was successfully obtained. XRD proved that the crystal structure of ACNC II with various DS values was maintained after acetylation. TEM showed the threadlike shape for ACNC II with various DS values. The ACNC II with various DS values was introduced into a polylactic acid (PLA) matrix to produce PLA/ACNC composite films, which showed improved rheological and thermal properties. This improvement was primarily attributed to good dispersion of the ACNC II, and the interfacial compatibility between ACNC II and the PLA matrix. This study aims to analyze the compatibility of ACNC II with various DS values in the PLA matrix by microstructure, crystallization, and rheological and thermal tests.

Esterification of Cochineal Carmine Used for Dyeing Cationic Modified Cotton with High Color Fastness

In order to reduce the electronic cloud density for higher color fastness, ester groups were introduced into cochineal carmine matrix structure. The optimum esterification conditions were selected by varying the level of acid-binding agent, the reaction temperature, the reaction time, and the amount of acetylation reagent. The structure and properties of esterified cochineal carmine was characterized by UV-vis spectroscopy, FT-IR spectrometry and metallographic microscopy. The build-up property, dyeability, light fastness, perspiration and rubbing fastness of cochineal carmine before and after esterification on cationic modified cotton were investigated. The results show that the optimum esterification condition is treating 1.0 g cochineal carmine with 50 mL acetic anhydride and 4.0 g anhydrous sodium acetate at 80°C for 2.0 hours. The acid perspiration fastness and wet rubbing fastness of the resulting dyed samples were increased by one grade. The perspiration fastness to alkalis and the light fastness were improved by one-half grade.

Selective Acetylation of 2-Naphthol to 2-Naphthyl Acetate with Ni Homogeneous Catalysts: An Environmentally Friendly Protocol

An efficient, selective and simple route for the synthesis of 2-Naphthyl acetate has been developed. In reflux conditions the acetylation of 2-naphthol acetylation with a catalytic amount of Nickel nitrate catalysts afforded 2-Naphthyl acetate in moderate to excellent yields. Nickel nitrate showed the best catalytic performance compared to other Nickel salts. Different weights of nickel salts have been evaluated for the title reaction with 30mg NiNO3 afforded the Best conversions. Different acylating reagents were evaluated acetic acid, acetyl chloride and acetic anhydride, and it was observed that acetic acid was the best acetylating reagent. The protocol has advantages including short reaction times, high chemoselectivity towards acylated product simple work-up. Additionally, nickel nitrate, other additives are not required to enhance the reactions.

Preparation of an Efficient Oil-Spill Adsorbent Based on Wheat Straw

Acetylation of cellulose fiber extracted by methylbenzene/ethanol (2/1), sodium chlorite solution, and sodium hydroxide from raw wheat straw (RWS) was studied to examine its potential as an oil-spill adsorbent. Wheat straw cellulosic sorbent was produced by using acetic anhydride as an acetylating reagent and N-bromosuccinimide (NBS) as a catalyst. Effects of the volume ratio of acetic anhydride (from 6.25% to 57.5%), catalyst concentration (from 10 to 60 mM NBS), reaction temperature (from 50 to 120 °C), and reaction time (from 0.5 to 3 h) on oil-sorption properties were evaluated. The best oil absorbencies for diesel fuel, diesel oil slick, corn oil, and corn oil slick treatments were 24.21 ± 0.76, 22.39 ± 0.77, 25.61 ± 2.13, and 24.73 ± 1.19 g/g, respectively. Chemical composition and morphologic structure of RWS before and after acetylation were investigated and compared. Oil-absorption capacity, oil-retention ability, recyclability, and selectivity of RWS, pretreated wheat straw, and acetylated wheat straw were also discussed. The acetylated wheat straw demonstrated good potential for the utilization of agricultural residues as natural sorbents in oil cleanup.

Acetic anhydride at 100 K: the first crystal structure determination.

Acetic anhydride (ethanoic anhydride), (CH3CO)2O, is a widely used acetylation reagent in organic synthesis. The crystal and molecular structure, as determined by single-crystal X-ray analysis at 100 K, is reported for the first time. A crystal of the title compound (m.p. 200 K) suitable for X-ray diffraction was grown from the melt at low temperature. The title compound crystallizes in the orthorhombic space group Pbcn, with Z = 4. In the crystal, the molecule adopts an exact C2-symmetric conformation about a crystallographic twofold axis. The molecules are densely packed. Two of the methyl H atoms form short intermolecular contacts to a neighbouring carbonyl O atom, which can be viewed as weak hydrogen bonds.

SiO2@FeSO4 NANO COMPOSITE AS NANOCATALYST FOR THE GREEN SYNTHESIS 1,1-DIACETATES FROM ALDEHYDES UNDER SOLVENT-FREE CONDITIONS

Aldehydes compounds selective converted to 1,1-diacetates as protective reagent with SiO 2 @FeSO 4 nano composite as effective nano catalyst at room temperature under solvent-free condition and acetic anhydride (Ac 2 O) as acetylation reagent. This method provides several advantages, such as low cost of the nano catalyst, high yields, short reaction time, chemoselective protection of aldehydes and operational simplicity. Aromatic and aliphatic, simple and conjugated aldehydes were protected with excellent yields. In addition, chemoselective reductive acetylation of aldehydes over ketones was achieved perfectly with the reagent at room temperature. Scheme 1. Synthesis of 1,1-diacetates from aldehydes.

Synthesis and characterization of Cp2Zr(C9H9O)2: a new zirconocene derivative catalyzed acetylation of 2-naphtol and benzyl alcohol

The new zirconocene compound, Cp2Zr(C9H9O)2, was successfully prepared from the reaction of zirconocene dichloride with 1-indanol in 1:2 molar ratio in dry chloroform at the presence of triethylamine (Et3N) and in an inert atmosphere. This compound was characterized by (1H and 13C) NMR, elemental analysis, FT-IR, UV–Vis, TGA and mass spectrum data. The catalytic activity of the synthesized compound for the acetylation of 2-naphtol and benzyl alcohol with acetic anhydride as an acetylating reagent in the solvent free conditions was also investigated. The Cp2Zr(C9H9O)2 as a catalyst affords an efficient and simple method for the acetylation of 2-naphtol and benzyl alcohol.