Showing papers on "Carboxylic acid published in 2019"
TL;DR: An asymmetric C(sp3 )-H amidation of thioamides using an achiral CoIII /chiral carboxylic acid hybrid catalytic system, which provides easy and straightforward access to chiral β-amino thiocarbonyl and β- amino carbonyl building blocks with a quaternary carbon stereocenter is described.
Abstract: Recent advances in Cpx MIII catalysis (M=Co, Rh, Ir) have enabled a variety of enantioselective C(sp2 )-H functionalization reactions, but enantioselective C(sp3 )-H functionalization is still largely unexplored. We describe an asymmetric C(sp3 )-H amidation of thioamides using an achiral CoIII /chiral carboxylic acid hybrid catalytic system, which provides easy and straightforward access to chiral β-amino thiocarbonyl and β-amino carbonyl building blocks with a quaternary carbon stereocenter.
180 citations
TL;DR: A visible-light-mediated carboxylation of benzylic C–H bonds with CO2 into 2-arylpropionic acids under metal-free conditions is reported.
Abstract: The carboxylation of sp3-hybridized C-H bonds with CO2 is a challenging transformation. Herein, we report a visible-light-mediated carboxylation of benzylic C-H bonds with CO2 into 2-arylpropionic acids under metal-free conditions. Photo-oxidized triisopropylsilanethiol was used as the hydrogen atom transfer catalyst to afford a benzylic radical that accepts an electron from the reduced form of 2,3,4,6-tetra(9H-carbazol-9-yl)-5-(1-phenylethyl)benzonitrile generated in situ. The resulting benzylic carbanion reacts with CO2 to generate the corresponding carboxylic acid after protonation. The reaction proceeded without the addition of any sacrificial electron donor, electron acceptor or stoichiometric additives. Moderate to good yields of the desired products were obtained in a broad substrate scope. Several drugs were successfully synthesized using the novel strategy.
166 citations
TL;DR: The thermal and long-term stability of carboxylic acid-choline chloride (ChCl) solvents has been investigated in this paper, showing that the mixture of choline chloride and carboxyl acid is stable.
Abstract: Mixtures of carboxylic acids and choline chloride are one of the most commonly used families of deep-eutectic solvents. The thermal and long-term stability of carboxylic acid–choline chloride (ChCl...
143 citations
TL;DR: In this paper, the influence of functional group types on acid and their molar ratios with hydrogen bond acceptor on lignin extraction were evaluated, and the result showed presence of hydroxyl group and short alkyl chain enhanced biomass fractionation.
141 citations
TL;DR: In this article, an innocuous weak acid (citric acid) was applied to prepare cellulose nanocrystals (CNCs) and cellulose nibrils (CNFs) from bleached bagasse pulp accompanied by simultaneous modifications of the functional groups on their molecular interface.
114 citations
TL;DR: In this paper, solvent developments for liquid-liquid extraction (LLX) of carboxylic acids are reviewed, and regeneration strategies are discussed, aiming to provide direction towards regenerations that do not further dilute streams that are already diluted before the LLX process.
107 citations
TL;DR: Benefiting from the uncoordinated carboxylate sites in the framework, JLU-MOF71 not only can sensitively detect trace amounts of individual Fe3+ and 2,4,6-trinitrophenol (TNP) through luminescence quenching but also exhibits high selectivity when other competing analytes exist.
Abstract: By using the mixed-linker strategy, a new pillar-layered luminescence Zn-LMOF (JLU-MOF71) ([Zn2Na2(TPHC)(4,4-Bipy)(DMF)]·8H2O) (TPHC = [1,1′:2′,1″-terphenyl]-3,3″,4,4′,4″,5′-hexacarboxylic acid, 4,...
99 citations
TL;DR: A ketone synthesis that couples two different carboxylic acid esters, N-hydroxyphthalimide esters and S-2-pyridyl thioesters, to form aryl-alkyl and dialkyl ketones in high yields is demonstrated.
Abstract: Synthesis of the C-C bonds of ketones relies upon one high-availability reagent (carboxylic acids) and one low-availability reagent (organometallic reagents or alkyl iodides) We demonstrate here a ketone synthesis that couples two different carboxylic acid esters, N-hydroxyphthalimide esters and S-2-pyridyl thioesters, to form aryl alkyl and dialkyl ketones in high yields The keys to this approach are the use of a nickel catalyst with an electron-poor bipyridine or terpyridine ligand, a THF/DMA mixed solvent system, and ZnCl2 to enhance the reactivity of the NHP ester The resulting reaction can be used to form ketones that have previously been difficult to access, such as hindered tertiary/tertiary ketones with strained rings and ketones with α-heteroatoms The conditions can be employed in the coupling of complex fragments, including a 20-mer peptide fragment analog of Exendin(9-39) on solid support
77 citations
TL;DR: Two complementary one-pot systems in which the reductive aminase (RedAm) from Aspergillus oryzae is combined with either a 1° alcohol/alcohol oxidase (AO) or carboxylic acid/carboxy Lic acid reductase (CAR) to affect N-alkylation reactions are reported.
Abstract: The alkylation of amines with either alcohols or carboxylic acids represents a mild and safe alternative to the use of genotoxic alkyl halides and sulfonate esters. Here we report two complementary one-pot systems in which the reductive aminase (RedAm) from Aspergillus oryzae is combined with either (i) a 1° alcohol/alcohol oxidase (AO) or (ii) carboxylic acid/carboxylic acid reductase (CAR) to affect N-alkylation reactions. The application of both approaches has been exemplified with respect to substrate scope and also preparative scale synthesis. These new biocatalytic methods address issues facing alternative traditional synthetic protocols such as harsh conditions, overalkylation and complicated workup procedures.
75 citations
TL;DR: The catalytic enantioselective directed methylene C(sp 3 )-H amidation reactions of 8-alkylquinolines using a Cp*Rh III /chiral carboxylic acid (CCA) hybrid catalytic system is described.
Abstract: Catalytic enantioselective directed methylene C(sp3 )-H amidation reactions of 8-alkylquinolines using a Cp*RhIII /chiral carboxylic acid (CCA) hybrid catalytic system are described. A binaphthyl-based chiral carboxylic acid efficiently differentiates between the enantiotopic methylene C-H bonds, which leads to the formation of C-N bonds with good enantioselectivity.
73 citations
TL;DR: A base-free, nickel-catalyzed decarbonylative coupling of carboxylic acid fluorides with diboron reagents to selectively afford aryl boronate ester products is developed.
Abstract: This Article describes the development of a base-free, nickel-catalyzed decarbonylative coupling of carboxylic acid fluorides with diboron reagents to selectively afford aryl boronate ester product...
TL;DR: These copper(II) derivatives efficiently catalyze the oxidation of cycloalkanes with hydrogen peroxide under mild conditions and opening up their use as multicarboxylate ligands toward the design of copper-organic architectures.
Abstract: A three-component aqueous reaction system comprising copper(II) acetate (metal node), poly(carboxylic acid) with a phenylpyridine or biphenyl core (main building block), and 1,10-phenanthroline (crystallization mediator) was investigated under hydrothermal conditions. As a result, four new coordination compounds were self-assembled, namely, {[Cu(μ3-cpna)(phen)]·H2O}n (1), {[Cu(μ-Hbtc)(phen)]·H2O}n (2), {[Cu(μ3-Hcpic)(phen)]·2H2O}n (3), and [Cu6(μ-Hcptc)6(phen)6]·6H2O (4), where H2cpna = 5-(2′-carboxylphenyl)nicotinic acid, H3btc = biphenyl-2,4,4′-tricarboxylic acid, H3cpic = 4-(5-carboxypyridin-2-yl)isophthalic acid, H3cptc = 2-(4-carboxypyridin-3-yl)terephthalic acid, and phen = 1,10-phenanthroline. Crystal structures of compounds 1–3 reveal that they are 1D coordination polymers with a ladder, linear, or double-chain structure, while product 4 is a 0D hexanuclear complex. All of the structures are extended further [1D → 2D (1 and 2), 1D → 3D (3), and 0D → 3D (4)] into hydrogen-bonded networks. The type ...
TL;DR: Acid fluorides, which can be derived from carboxylic acids, show good stability and high reactivity in a wide range of possible functionalizations with nucleophiles, and their use provides an interesting alternative to that of the parent car boxylic acid derivatives.
Abstract: Several recent reports outlined the singular reactivity of acid fluorides as excellent electrophiles in transition-metal catalysis. These species undergo oxidative addition of the metal into the C-F bond; then, retention or release of the CO moiety can occur and be controlled by tuning the catalytic system and the reaction parameters. Acid fluorides, which can be derived from carboxylic acids, show good stability and high reactivity in a wide range of possible functionalizations with nucleophiles. Their use provides an interesting alternative to that of the parent carboxylic acid derivatives (acid chlorides, esters, amides, acids, or aldehydes).
TL;DR: The NH2@COF-SPE method is an efficient pretreatment procedure and can be utilized for the selective extraction of carboxylic acid pesticides from environmental water samples.
TL;DR: A mechanistically guided strategy to improve reductive carboxylations through the use of a homogeneous organic reductant is described, which may be broadly translatable to a wide range of cross-electrophile coupling reactions.
Abstract: The nickel-catalyzed carboxylation of organic halides or pseudohalides using carbon dioxide is an emerging method to prepare synthetically valuable carboxylic acids. Here, we report a detailed mechanistic investigation of these reactions using the carboxylation of aryl halides with (PPh3)2NiIICl2 as a model reaction. Our studies allow us to understand several general features of nickel-catalyzed carboxylation reactions. For example, we demonstrate that both a Lewis acid and halide source are beneficial for catalysis. To this end, we establish that heterogeneous Mn(0) and Zn(0) reductants are multifaceted reagents that generate noninnocent Mn(II) or Zn(II) Lewis acids upon oxidation. In a key result, a rare example of a well-defined nickel(I) aryl complex is isolated, and it is demonstrated that its reaction with carbon dioxide results in the formation of a carboxylic acid in high yield (after workup). The carbon dioxide insertion product undergoes rapid decomposition, which ca These three oxidation states correspond to the onbe circumvented by a ligand metathesis reaction with a halide source. Our studies have led to both a revised mechanism and the development of a broadly applicable strategy to improve reductive carboxylation reactions. A critical component of this strategy is that we have replaced the heterogeneous Mn(0) reductant typically used in catalysis with a well-defined homogeneous organic reductant. Through its use, we have increased the range of ancillary ligands, additives, and substrates that are compatible with the reaction. This has enabled us to perform reductive carboxylations at low catalyst loadings. Additionally, we demonstrate that reductive carboxylations of organic (pseudo)halides can be achieved in high yields in more practically useful, non-amide solvents. Our results describe a mechanistically guided strategy to improve reductive carboxylations through the use of a homogeneous organic reductant, which may be broadly translatable to a wide range of cross-electrophile coupling reactions.
TL;DR: This review detail developments in the enzyme-catalyzed preparation of secondary and tertiary amides for the synthesis of pharmaceutical-type molecules and review the applications of hydrolases, such as lipases and penicillin acylases, to these reactions.
Abstract: The synthesis of the amide bond between an amine and a carboxylic acid is one of the most significant reactions in industrial pharmaceutical synthesis. Despite the apparent simplicity of synthetic methods for amide bond formation, many of these are disadvantaged by their requirement for toxic or hazardous reagents for the activation of the acid component, or poor atom economy resulting from the need for stoichiometric amounts of coupling reagents. In this context, biocatalysis has emerged as an alternative catalytic method for amide bond formation, presenting the advantages of both environmentally benign reagents and conditions and also atom economy. In this review we detail developments in the enzyme-catalyzed preparation of secondary and tertiary amides for the synthesis of pharmaceutical-type molecules and review the applications of hydrolases, such as lipases and penicillin acylases, to these reactions. We also summarise the activity of ATP-dependent enzymes for amide bond formation and assess their potential for the preparative synthesis of amides from carboxylic acids and amines in aqueous media. Keywords: Biocatalysis, Amides, Lipase, Penicillin Acylase, NRPS, Amide Bond Synthetase
TL;DR: The proton conductivity of barium-based MOFs MFM-510 to M FM-512 are analysed in relation to the absence and presence of free –COOH groups in the pores.
Abstract: Three multi-carboxylic acid functionalised ligands have been designed, synthesised and utilised to prepare the new barium-based MOFs, MFM-510, -511, and -512, which show excellent stability to water-vapour. MFM-510 and MFM-511 show moderate proton conductivities (2.1 × 10−5 and 5.1 × 10−5 S cm−1, respectively) at 99% RH and 298 K, attributed to the lack of free protons or hindered proton diffusion within the framework structures. In contrast, MFM-512, which incorporates a pendant carboxylic acid group directed into the pore of the framework, shows a two orders of magnitude enhancement in proton conductivity (2.9 × 10−3 S cm−1). Quasi-elastic neutron scattering (QENS) suggests that the proton dynamics of MFM-512 are mediated by “free diffusion inside a sphere” confirming that incorporation of free carboxylic acid groups within the pores of MOFs is an efficient albeit synthetically challenging strategy to improve proton conductivity.
TL;DR: In this paper, the molar ratio of hydrogen bond acceptor (HBA) to hydrogen bond donor (HBD) was taken in the range from 1:1 to 1:4.
TL;DR: The polybasic carboxylic acid (HCPVC) consisting of vanillin and hexachlorocyclotriphosphazene was synthesized successfully by the nucleophilic substitution reaction and the Pinnick oxidation as discussed by the authors.
Abstract: The novel polybasic carboxylic acid (HCPVC) consisting of vanillin and hexachlorocyclotriphosphazene was synthesized successfully by the nucleophilic substitution reaction and the Pinnick oxidation...
TL;DR: Modeling the adsorption of formic acid on top of (101) anatase surfaces, it is shown that the anatase surface acts like a protecting group for the carboxylic acid functionality.
Abstract: Carboxylic-acid adsorption on anatase TiO2 is a relevant process in many technological applications. Yet, despite several decades of investigations, the acid-proton localization-either on the molecule or on the surface-is still an open issue. By modeling the adsorption of formic acid on top of anatase(101) surfaces, we highlight the formation of a short strong hydrogen bond. In the 0 K limit, the acid-proton behavior is ruled by quantum delocalization effects in a single potential well, while at ambient conditions, the proton undergoes a rapid classical shuttling in a shallow two-well free-energy profile. This picture, supported by agreement with available experiments, shows that the anatase surface acts like a protecting group for the carboxylic acid functionality. Such a new conceptual insight might help rationalize chemical processes involving carboxylic acids on oxide surfaces.
TL;DR: ODDA-PTX shows differentiated pharmacokinetics, higher maximum tolerated doses and increased efficacy in vivo in multiple subcutaneous murine xenograft models of human cancer, as compared to two FDA-approved clinical formulations.
Abstract: We describe the design, synthesis, and antitumor activity of an 18 carbon α,ω-dicarboxylic acid monoconjugated via an ester linkage to paclitaxel (PTX). This 1,18-octadecanedioic acid-PTX (ODDA-PTX) prodrug readily forms a noncovalent complex with human serum albumin (HSA). Preservation of the terminal carboxylic acid moiety on ODDA-PTX enables binding to HSA in the same manner as native long-chain fatty acids (LCFAs), within hydrophobic pockets, maintaining favorable electrostatic contacts between the ω-carboxylate of ODDA-PTX and positively charged amino acid residues of the protein. This carrier strategy for small molecule drugs is based on naturally evolved interactions between LCFAs and HSA, demonstrated here for PTX. ODDA-PTX shows differentiated pharmacokinetics, higher maximum tolerated doses and increased efficacy in vivo in multiple subcutaneous murine xenograft models of human cancer, as compared to two FDA-approved clinical formulations, Cremophor EL-formulated paclitaxel (crPTX) and Abraxane (nanoparticle albumin-bound (nab)-paclitaxel).
TL;DR: Directed ortho metalation or nucleophilic acyl substitution can be efficiently programmed on the same aromatic carboxylic acid amide, in a choline chloride-based eutectic mixture, by simply switching the nature of the organolithium reagent.
TL;DR: In this paper, the physicochemical properties of eight prepared deep eutectic solvents (NADES) were measured as functions of temperature and water content, and the ORAC values indicated that the tested NADES displayed antioxidative activity.
Abstract: Natural deep eutectic solvents (NADES) may be considered ‘designer solvents’ due to their numerous structural variations and the possibility of tailoring their physicochemical properties. Prior to their industrial application, characterization of NADES is essential, including determination of their physicochemical properties, cytotoxicity, and antioxidative activity. The most important physicochemical properties of eight prepared NADES (choline chloride:malic acid, proline:malic acid, choline chloride:proline:malic acid, betaine:malic acid, malic acid:glucose, malic acid:glucose:glycerol, choline chloride:citric acid, and betaine:citric acid) were measured as functions of temperature and water content. In general, the structure of prepared NADES greatly influences their physical properties, which could be successfully modified and adjusted by addition of water. All tested NADES were absolutely benign and noncorrosive for investigated steel X6CrNiTi18-10. Furthermore, cytotoxicity of prepared solvents was assessed toward three human cell lines (HEK-293T, HeLa, and MCF-7 cells), and antioxidative activity was measured by the Oxygen Radical Absorbance Capacity (ORAC) method. With regard to cell viability, all tested NADES containing carboxylic acid could be classified as practically harmless and considered environmentally safe. The ORAC values indicated that the tested NADES displayed antioxidative activity.
TL;DR: In this article, a family of hierarchical macroporous-mesoporous SBA-15 sulfonic acids were prepared with tunable macropore diameters for carboxylic acid esterification.
Abstract: Bio-derived platform chemicals and fuels are important for the development of sustainable manufacturing. However, their efficient production from biomass necessitates new catalysts and processes optimised for the selective transformation of large molecules. Mesoporous and hierarchically porous functional materials are promising catalyst candidates for biomass valorisation, but quantitative relationships between pore dimensions/connectivity, mass transport, and corresponding catalytic performance are poorly defined. A family of hierarchical macroporous–mesoporous SBA-15 sulfonic acids were prepared with tunable macropore diameters for carboxylic acid esterification. Turnover frequencies for long-chain (palmitic and erucic) acids were proportional to macropore diameter (≤370 nm), whereas propanoic acid esterification was independent of macropore size. Pulsed field gradient NMR diffusion experiments reveal that larger macropores enhance esterification of bulky carboxylic acids by conferring superior pore interconnectivity and associated mass transport.
TL;DR: This work will open a new avenue for proton conductive MOF-based impedance sensors and promote the potential application of these MOFs in indirect monitoring the concentrations of formic acid vapors.
Abstract: Metal-organic frameworks (MOFs) have been extensively explored as advanced chemical sensors in recent years. However, there are few studies on MOFs as acidic gas sensors, especially proton conductive MOFs. In this work, two new proton-conducting 3D MOFs, {[Co3 (p-CPhHIDC)2 (4,4'-bipy)(H2 O)]⋅2 H2 O}n (1) (p-CPhH4 IDC=2-(4-carboxylphenyl)-1 H-imidazole-4,5-dicarboxylic acid; 4,4'-bipy=4,4'-bipyridine) and {[Co3 (p-CPhHIDC)2 (bpe)(H2 O)]⋅3 H2 O}n (2) (bpe=trans-1,2-bis(4-pyridyl)ethylene) have been solvothermally prepared and investigated their formic acid sensing properties. Both MOFs 1 and 2 show temperature- and humidity-dependent proton conductive properties and exhibit optimized proton conductivities of 1.04×10-3 and 7.02×10-4 S cm at 98 % relative humidity (RH) and 100 °C, respectively. The large number of uncoordinated carboxylic acid sites, free and coordination water molecules, and hydrogen-bonding networks inside the frameworks are favorable to the proton transfer. By measuring the impedance values after exposure to formic acid vapor at 98 % or 68 % RH and 25 °C, both MOFs indicate reproducibly high sensitivity to the analyte. The detection limit of formic acid vapor is as low as 35 ppm for 1 and 70 ppm for 2. Meanwhile, both MOFs also show commendable selectivity towards formic acid among interfering solutions. The proton conducting and formic acid sensing mechanisms have been suggested according to the structural analysis, Ea calculations, N2 and water vapor absorptions, PXRD and SEM measurements. This work will open a new avenue for proton-conductive MOF-based impedance sensors and promote the potential application of these MOFs for indirectly monitoring the concentrations of formic acid vapors.
TL;DR: Developed a simple esterification route to obtain lignin derivatives with tunable Tg's and low E-factor reactions.
TL;DR: N, O-Bidentate directing-enabled, traceless heterocycle synthesis is described via Cp*-free cobalt-catalyzed C-H activation/annulation and shows a broad substrate scope with the products obtained in good to excellent yields.
TL;DR: In this paper, the authors synthesize palladium aerogels assembled by nanosheets in four various carboxylic acid (RCOOH) solvents with different alkyl groups (R= H− (formic acid, FA), CH3− (acetic acid, AA), CH 3− (propionic acid, PA), and CH3CH2CH2− (butyric acid, BA)).
Abstract: Three-dimensional noble metal aerogels are unique solid materials with ultralow densities, large open pores, and high surface areas. Despite several research works on noble metal aerogels assembled by nanochains, the investigation of noble metal aerogels assembled by nanosheets has not been reported to date. In this work, palladium aerogels assembled by nanosheets have been synthesized in four various carboxylic acid (RCOOH) solvents with different alkyl groups (R= H– (formic acid, FA), CH3– (acetic acid, AA), CH3CH2– (propionic acid, PA), and CH3CH2CH2– (butyric acid, BA)). It has been found that the R groups play a crucial role in the morphology of palladium aerogels so that the Pd aerogels synthesized in acetic acid and propionic acid solvents show better morphology than that of palladium aerogels synthesized in formic acid and butyric acid solvents. The electrocatalytic activity and durability of all aerogels are evaluated using cyclic voltammetry (CV) and chronoamperometry (CA) experiments toward ethanol oxidation. Based on CV and CA data, Pd aerogels synthesized in AA and PA show high catalytic activity and durability due to their unique structures.
TL;DR: The surface chemistry of colloidal cesium lead bromide (CsPbBr3) nanocrystals is decisive in determining the stability and final morphology of this class of materials, characterized by ionic structure and a high defect tolerance factor as discussed by the authors.
Abstract: The surface chemistry of colloidal cesium lead bromide (CsPbBr3) nanocrystals is decisive in determining the stability and the final morphology of this class of materials, characterized by ionic structure and a high defect tolerance factor Here, the high sensitivity of purified colloidal nanocubes of CsPbBr3 to diverse environmental condition (solvent dilution, ageing, ligands post synthetic treatment) in ambient atmosphere is investigated by means of a comprehensive morphological (electron microscopy), structural (θ/2θ X-ray diffraction (XRD) and grazing incidence wide angle scattering (GIWAXS)), and spectroscopic chemical (1H nuclear magnetic resonance (NMR), nuclear Overhauser effect spectroscopy (NOESY), absorption and emission spectroscopy) characterization The aging and solvent dilution contribute to modify the nanocrystal morphology, due to a modification of the ligand dynamic Moreover, we establish the ability of aliphatic carboxylic acids and alkyl amines ligands to induce, even in a post preparative process at room temperature, structural, morphological and spectroscopic variations Upon post synthesis alkyl amine addition, in particular of oleyl amine and octyl amine, the highly green emitting CsPbBr3 nanocubes effectively turn into one-dimensional (1D) thin tetragonal nanowires or lead halide deficient rhombohedral zero-dimensional (0D) Cs4PbBr6 structures with a complete loss of fluorescence The addition of an alkyl carboxylic acid, as oleic and nonanoic acid, produces the transformation of nanocubes into still emitting orthorombic two-dimensional (2D) nanoplates The acid/base equilibrium between the native and added ligands, the adsorbed/free ligands dynamic in solution and the ligand solubility in non-polar solvent contribute to render CsPbBr3 particularly sensitive to environmental and processing conditions and, therefore prone to undergo to structural, morphological and, hence spectroscopic, transformations
TL;DR: The present study indicates that the delivery of Cur-NPs to breast cancer using carboxylic acid-functionalized HA carrier could improve their anti-cancer activities.