Acylating Reagents Research Articles

Dimensional stabilization of wood by chemical modification using isopropenyl acetate

Chemical modification of wood with isopropenyl acetate (IPA) using iodine (I2) as catalyst has been carried out. Rubber wood (Hevea brasiliensis) specimens were reacted with IPA using iodine (I2) catalyst at 95°C up to 10 h under solvent free conditions. The effect of catalyst concentration and reaction time was studied. The extent of acetylation was measured by determining weight percent gain and the modified wood was characterized by FTIR-ATR and 13C NMR spectroscopy. It was found that IPA in the presence of iodine is an excellent acylating reagent for wood. Modified wood exhibited high dimensional stability.

Time and energy-efficient homogeneous transesterification of cellulose under mild reaction conditions

In this research, cellulose aliphatic esters (CEs) were synthesized efficiently in an N, N-dimethylacetamide/lithium chloride system (DMAc/LiCl) with vinyl esters (VEs, number of carbon atoms ranging from 4 to 12) as acylation reagent and 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) as catalyst. The structures and properties of the products have been characterized by various analytical techniques. The key concept in this cellulose modification was the achievement the degree of substitution (DS) >2.75 at much milder temperature and shorter reaction time (under 30°C within 15min–30min), other than previous research. Generally, the DS of obtained CEs showed a reverse trend with the length of the aliphatic chain increasing. The priority of reactions in three positions of the CEs followed the same order of C6>C2>C3 for a homogeneous conversion. There was no decrease of molecule weight under this mild reaction. This research provides a novel homogeneous technology to synthesize various CEs efficiently.

Diacyl Disulfide: A Reagent for Chemoselective Acylation of Phenols Enabled by 4-(N,N-Dimethylamino)pyridine Catalysis.

A general and excellent acylation reagent, diacyl disulfide, was uncovered for efficient ester formation enabled by DMAP (4-(N,N-dimethylamino)pyridine) catalysis. This protocol offered a promising synthetic platform on site-selective acylation of phenolic and primary aliphatic hydroxyl groups, which greatly expanded the realm of protecting group chemistry. The importance of the reagent was also reflected by its excellent moisture tolerance, high efficiency, and potential in synthetic chemistry and biologically meaningful natural product modification.

Mild Acylation of C(sp3)–H and C(sp2)–H Bonds under Redox-Neutral Rh(III) Catalysis

Carbonyl groups are ubiquitous in functional molecules. Although C–H bond acylation has been well-studied via different mechanisms, transition-metal-catalyzed redox-neutral C(sp3)–H acylation under mild conditions is unprecedented. In this work, ketene is designed as a acylating reagent for both C(sp3)–H and C(sp2)–H bonds under Rh(III) catalysis, affording a diverse array of carbonyl compounds in high yields and high atom economy under mild conditions.

ChemInform Abstract: Sterically‐Controlled Intermolecular Friedel—Crafts Acylation with Twisted Amides via Selective N—C Cleavage under Mild Conditions.

Highly chemoselective Friedel–Crafts acylation with twisted amides under mild conditions is reported for the first time. The reaction shows high functional group tolerance, obviating the need for preformed sensitive organometallic reagents and expensive transition metal catalysts. The high reactivity of amides is switched on by ground-state steric distortion to disrupt the amide bond nN → πCO* resonance as a critical design feature. Conceptually, this new acid-promoted mechanism of twisted amides provides direct access to bench-stable acylating reagents under mild, metal-free conditions.

ChemInform Abstract: Chemoselective Ketone Synthesis by the Addition of Organometallics to N‐Acylazetidines.

A general and highly chemoselective method for the synthesis of ketones by the addition of organometallics to N-acylazetidines via stable tetrahedral intermediates is reported for the first time. The transformation is characterized by its wide substrate scope and exquisite selectivity for the ketone products even when a large excess of nucleophilic reagents is used. Even of broader interest is the use of N-acylazetidines as bench-stable, readily available amide acylating reagents, in which the reactivity is controlled by amide pyramidalization and strain of the four-membered ring to afford synthetically valuable building blocks.

ChemInform Abstract: Interaction of 3‐(2‐Aminophenyl)‐6‐R1‐1,2,4‐triazin‐5‐ones with Acylating Reagents: An Efficient Method for Preparation of 6‐Substituted 3‐R1‐2H‐[1,2,4]Triazino[2,3‐c]quinazolin‐2‐ones.

The series of 6-substituted 3-R1-2H-[1,2,4]triazino[2,3-c]quinazolin-2-one was prepared via condensation of 3-(2-aminophenyl)-6-R1-1,2,4-triazin-5-ones with acylating reagents. Particularities of 1H NMR spectra have been also discussed based on the comparison of experimental and theoretical results for 3-methyl-6-phenyl-2H-[1,2,4]triazino[2,3-c]quinazolin-2-one and its 4,3-isomer.

Regioselective ortho‐Acylation of N‐Aryl‐1,2,3‐triazoles with Alcohols in Water

A palladium‐catalyzed regioselective ortho‐acylation of N‐aryl‐1,2,3‐triazoles has been achieved under aqueous conditions without the assistance of surfactants or additives. The reaction takes place by using benzylic, heterocyclic, and aliphatic alcohols as the acylating reagents and tert‐butyl hydroperoxide (TBHP) as the oxidant and provides an alternative route for the synthesis of triazole‐substituted aryl, heteroaryl, and aliphatic ketones in moderate to excellent yields.

In situ sonochemical reduction and direct functionalization of graphene oxide: A robust approach with thermal and biomedical applications

The rapid, robust, scalable and non-hazardous sonochemical approach for in situ reduction and direct functionalization of graphene oxide has been developed for non-toxic biomedical applications. The graphene oxide (GrO) was directly functionalized with tryptamine (TA) without using any hazardous acylating and coupling reagents. The reaction was completed within 20min. An impact of ultrasound was inferred for a direct functionalization with other conventional methods. The evolved electronic states were confirmed with near edge X-ray absorption fine structure (NEXAFS). The direct covalent functionalization and formation of f-(TA) GrO was proven with FTIR, 13C solid state NMR, XPS, XRD, Raman‚ HRTEM, AFM and TGA. The total percentage weight loss in TGA confirms an enhanced thermal stability of f-(TA) GrO. The f-(TA) GrO was further explored for an investigation of in vitro antimicrobial activity to ensure the health and environmental safety. An outstanding antibacterial activity of f-(TA) GrO was found against gram positive Staphylococcus aureus at MIC 128mgmL−1. It confirms a suitability of f-(TA) GrO for thermally stable antibacterial coating. The f-(TA) GrO showed 39.14–48.9% antioxidant activities, evaluated with 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical assay. The inherent cytotoxicity of f-(TA) GrO was evaluated with SRB assay to living cells, MCF-7 and Vero. The estimated cell viabilities were >80% upon addition of f-(TA) GrO over a wide concentration range of 10–80μgmL−1. The high cytocompatibility of f-(TA) GrO confirms the low toxicity and an excellent biocompatibility. The morphological effect on Vero cell line, evidently confirmed the biocompatibility of f-(TA) GrO. Therefore, f-(TA) GrO was emerged as an advanced functional biomaterial for thermal and biomedical applications.

Chemoselective Ketone Synthesis by the Addition of Organometallics to N-Acylazetidines.

A general and highly chemoselective method for the synthesis of ketones by the addition of organometallics to N-acylazetidines via stable tetrahedral intermediates is reported for the first time. The transformation is characterized by its wide substrate scope and exquisite selectivity for the ketone products even when a large excess of nucleophilic reagents is used. Even of broader interest is the use of N-acylazetidines as bench-stable, readily available amide acylating reagents, in which the reactivity is controlled by amide pyramidalization and strain of the four-membered ring to afford synthetically valuable building blocks.

Operationally Simple and Selective One-Pot Synthesis of Hydroxyphenones: A Facile Access to SNARF Dyes

High selectivity is observed during a Friedel–Crafts acylation/demethylation cascade. In contrast to this cascade, oxygen-containing acylating reagents do not undergo the demethylation step. By the methodology elaborated here, an access is provided to important intermediates for the total synthesis of seminaphthorhodafluor (SNARF) dyes.

Palladium-Catalyzed Sequential Acylation/Cyanation of Aryl Iodides: A Regiospecific Synthesis of 2-Cyanoaryl Ketones.

A palladium-catalyzed, norbornene-mediated acylation/cyanation reaction of iodobenzene was developed by the use of acyl chlorides as acylation reagents and cuprous cyanide. The reaction gave the 2-cyanoaryl ketones efficiently by using readily available starting materials.

Selective N-acetylation of aromatic amines using acetonitrile as acylating agent

A method for N-acetylation of amines has been developed using acetonitrile as an acylating agent and in situ generated trimethylsilyl iodide as the catalyst under microwave heating condition. The reaction is selective toward aromatic amines while aliphatic amines remain intact. The process eliminates the requirement of toxic acylating reagents like acetic anhydride and acetyl chloride.

Sterically-controlled intermolecular Friedel-Crafts acylation with twisted amides via selective N-C cleavage under mild conditions.

Highly chemoselective Friedel-Crafts acylation with twisted amides under mild conditions is reported for the first time. The reaction shows high functional group tolerance, obviating the need for preformed sensitive organometallic reagents and expensive transition metal catalysts. The high reactivity of amides is switched on by ground-state steric distortion to disrupt the amide bond nN→πCO* resonance as a critical design feature. Conceptually, this new acid-promoted mechanism of twisted amides provides direct access to bench-stable acylating reagents under mild, metal-free conditions.

N-Acyl-N-(4-chlorophenyl)-4-nitrobenzenesulfonamides: highly selective and efficient reagents for acylation of amines in water

Abstract A variety of N-acyl-N-(4-chlorophenyl)-4-nitrobenzenesulfonamides (1a–e) were synthesized in one pot from 4-chloroaniline under solvent-free conditions and have been developed as chemoselective N-acylation reagents. Selective protection of primary amines in the presence of secondary amines, acylation of aliphatic amines in the presence of aryl amines, and monofunctionalization of primary-secondary diamines as well as selective N-acylation of amino alcohols using these reagents are described. All of the acylation reactions were carried out in water as a green solvent. High stability and easy preparation of these acylating reagents are other advantages of this method.

Phosphonium alkyl PEG sulfate ionic liquids as coating materials for activation of Burkholderia cepacia lipase.

Lipases are among the most widely used enzymes applicable for various substrates; however, the slow reactions or poor enantioselective reactions are sometimes obtained. To develop ionic liquid type activating agents for lipase, four types of phosphonium cetyl(PEG)10 sulfate ionic liquids have been synthesized and used as coating materials of Burkholderia cepacia lipase (Lipase PS) through the lyophilization process. Tributyl ([2-methoxy]ethoxymethyl)phosphonium cetyl(PEG)10 sulfate ([P444MEM ][C16 (PEG)10 SO4 ]) (PL1) worked best among them, and PL1-coated lipase PS displayed high reactivity in transesterification of broad types of secondary alcohols using vinyl acetate as an acylating reagent with perfect enantioselectivity (E > 200). The substrate preference of PL1-PS differs from that of commercial lipase PS or [bdmim] [C16 (PEG)10 SO4 ]-coated lipase (IL1-PS); PL1-PS displayed excellent enantioselectivity in the reaction of 2-chloro-1-phenylethanol with E > 200, though insufficient E values were recorded for lipase PS (E = 12) and IL1-PS (E = 123) for this alcohol. PL1-PS also showed perfect enantioselectivity (E > 200) for the reaction of 1-(pyridin-2-yl)ethanol, while IL1-PS showed E = 130 for this compound. We further succeeded in demonstrating the recyclable use of PL1-PS five times in tributyl(3-methoxypropyl)phosphonium bis(trifluoromethylsulfonyl)amide ([P444PM ][Tf2 N]) as a solvent. Since PL1-PS is easily applicable to 10-20 gram-scaled reactions, it is expected that the IL-coated enzyme might be useful for practical preparation of a wide variety of chiral secondary alcohols.

N-acylation of amino-9,10-anthraquinones by the system of strong carboxylic acid – ammonium thiocyanate

The significance of the acylation reaction of amines is presented in the literary reference information. The products of the reaction of the corresponding amides are important intermediates in obtaining practically useful compounds. It has been shown that the most common methods of acylfunctionalization of amines are acetylation, trifluoroacetylation and formylation, usually acid anhydrides or chlorides are used as acylating reagents in these reactions in the presence of highly toxic and expensive catalysts. The authors have developed an approach to the synthesis of a number of N-acylated amino-9,10-anthraquinones, which is based on the use of a new acylation system consisting of a strong organic acid and ammonium thiocyanate. It has been determined that 1-amino-9,10-anthraquinone and its derivatives in the presence of the two-fold excess of ammonium thiocyanate can be acetylated only by formic and trifluoroacetic acids. 2-Amino-9,10-anthraquinone additionally can be acetylated by mercaptoacetic and acetic acids. The scheme of the reaction discovered has been proposed, it involves in situ generation of ammonium acetate from carboxylic acid and ammonium thiocyanate, which serves as the acylating reagent.

Palladium‐Catalyzed Catellani ortho‐Acylation Reaction: An Efficient and Regiospecific Synthesis of Diaryl Ketones

AbstractA palladium‐catalyzed, norbornene‐mediated Catellani ortho‐acylation reaction was developed by the use of either acyl chlorides or acid anhydrides as acylation reagents. The addition of more than a stoichiometric amount of H2O is crucial for this transformation when acid chlorides are used, and kinetic studies indicate that the active acylation reagent is possibly an acid anhydride.

Palladium-Catalyzed Catellani ortho-Acylation Reaction: An Efficient and Regiospecific Synthesis of Diaryl Ketones.

A palladium-catalyzed, norbornene-mediated Catellani ortho-acylation reaction was developed by the use of either acyl chlorides or acid anhydrides as acylation reagents. The addition of more than a stoichiometric amount of H2 O is crucial for this transformation when acid chlorides are used, and kinetic studies indicate that the active acylation reagent is possibly an acid anhydride.

Nature’s Treatment for Irritable Bowel Syndrome: Studies on the Isolation of (−)-Menthol from Peppermint Oil and Its Conversion to (−)-Menthyl Acetate

A simple, robust, and reproducible method was developed for the isolation of (−)-menthol from peppermint oil and to study the effect of different types of leaving groups, catalysts, solvents, and tertiary base on the extent of esterification of (−)-menthol to (−)-menthyl acetate. In this experiment, students compare leaving group properties of acetate and chloride ions from the acylating reagents acetic anhydride and acetyl chloride, respectively. The extent of conversion is compared when pyridine and 4-(dimethylamino)pyridine are used as catalysts, when N,N-diisopropylethylamine is used as tertiary base, and when the solvent is changed from dichloromethane to diethyl ether to N,N-dimethylformamide. Students are assessed on the chromatographic/spectroscopic purity and yield of (−)-menthol isolated and on their understanding of the factors that affect its extent of conversion to (−)-menthyl acetate. Full spectral characterization of both compounds is also conducted. They also complete a series of answers t...