Triethylammonium Formate Research Articles

A green and effective route leading to antiradical agents with 3-arylmethyl 4-hydroxyquinolin-2(1H)-one moiety

A new, green, convenient, cost- and atom effective route leading to 3-arylmethyl 4-hydroxyquinolin-2(1H)-ones from arylaldehydes and 1,3-dicarbonyl compounds in triethyl ammonium formate in good to excellent yield is presented. The provided method foresees the Knoevenagel condensation between a 4-hydroxyquinolin-2(1H)-one and an aromatic aldehyde followed by in situ trapping of the arylidene intermediate with the hydride ion. All synthesized compounds were tested for their antiradical activity against DPPH and GO free radicals. The antiradical activity of the 3-arylmethyl 4-hydroxyquinolin-2(1H)-ones was comparable to or even higher than that of some commercially widely used antioxidants like BHT, TBHQ, or α-tocopherol.

Studies of osmotic and activity coefficient properties of aqueous solutions of triethylammonium formate and triethylammonium glycolate protic ionic liquids at 298.15 K

The triethylammonium-based carboxylate protic ionic liquids (PILs) are called as truly bio-ionic liquids. They can be used as green solvent, additives (biphasic catalysis) and for other considerable effects involving nano-material specially related to biomolecules. In this work, osmotic coefficient (φ) measurements using vapor pressure osmometry technique for aqueous solutions of two PILs, namely, triethylammonium formate [TEAF] (0.01290–0.55988 mol·kg−1) and triethylammonium glycolate [TEAG] (0.00989–0.53176 mol·kg−1) have been reported at 298.15 K. The water activity (aw) and solvent activity coefficient (γ1), mean molal activity coefficient (γ±) of PILs and osmotic pressure (π) of solutions properties in a binary mixture, were determined using experimentally measured φ data. The analysis of osmotic pressure data revealed that the studied PILs are electrolytes in the limit of infinite dilution and yield correct molecular weights as well as show negative values for virial coefficients. The variations of osmotic coefficient and mean molal activity coefficient of studied PILs with concentration indicate positive deviations from Debye-Hückel limiting law similar to that of ammonium ions. Further, Gibbs free energy changes due to mixing (ΔGm) and excess Gibbs free energy changes (ΔGE) for the studied binary systems are estimated. The solute-solute virial coefficient (NB22∗0) for the studied PILs in aqueous solutions were estimated by an application of the McMillan−Mayer theory of solutions. The results indicate that the hydration effect is dominant in PILs through the cooperative H–bonding with water-structure making effect suggesting the significance of hydrophobic hydration as observed in tetraalkylammonium salts and aprotic ionic liquids. A need to study the water molecule splitting at nitrogen charge centre and possible attenuation of water structural effects due to hydrophobic moieties present in the molecule is emphasized.

Charge-based separation of synthetic macromolecules by non-aqueous ion exchange chromatography

Traditional polymer-separation methods, such as size-exclusion chromatography and (gradient) liquid adsorption chromatography, cannot provide separations exclusively based on the number of deprotonated carboxylic-acid groups along the backbone chain of polymers. A novel separation method, based on non-aqueous ion-exchange chromatography (NAIEX), was developed, which allows such a separation of acid-functional polymers that are soluble in organic solvents. The polar, aprotic N-methyl-2-pyrrolidone was found to be a suitable solvent. It features a high relative permittivity (favouring dissociation of ion pairs into free ions) and it is a good solvent for polymers and organic salts, such as triethyl-ammonium formate. A negative charge is established on these polymers by deprotonation of the carboxylic-acid groups in the presence of an organic superbase (tetramethyl guanidine). Traditional potent organic bases, such as triethylamine, do not possess the base strength to compensate for the increase in pKa of polymeric carboxylic acid groups in non-aqueous conditions. Triethyl-ammonium formate is proposed as an alternative to traditional salts used for elution in aqueous ion-exchange chromatography. Separation was performed on an industry-standard strong-anion-exchange column and (near-)universal detection of the polymers was performed by high-temperature evaporative-light-scattering detection. The NAIEX method yielded a separation based on the acid-functionality distribution of the polymer. NAIEX was compared with traditional normal- and reversed-phase liquid-chromatography approaches for the separation of acid-functional copolymers.

Mobility Analysis of Proteins by Charge Reduction in a Bipolar Electrospray Source.

Analysis of large electrosprayed biopolymers by electrical mobility alone is greatly facilitated by reducing their charge to unity. Here, we combine within a single chamber positive aqueous electrospray (ES), producing multiply charged protein cations, with negative methanolic ES, yielding small singly charged anions. Use of a 100 mM triethylammonium formate buffer in both solutions yields very small drops. The two sprays are decoupled electrostatically by an interposed 50% transparent, grounded metallic grid. This screen is readily crossed by the ions, resulting in substantial charge reduction. In spite of the grid, the aqueous spray is easily destabilized by the presence of anions in the positive ES region. Nonetheless, practical ES stabilization is achieved by using relatively small capillary tips (∼15 μm) in the positive emitter. Protein peaks obtained are as narrow as those previously reported via charge reduction with a radioactive Ni-63 source. Controlling the position of the negative ES permits spanning the full range of charge states, from high natural values to predominantly singly charged ions, even for large proteins such as immunoglobulin G (∼150 kDa).

Volumetric and compressibility studies of aqueous triethylammonium based protic ionic liquids at T = 298.15 K

The significant considerations have centred on the utilization of the bio-ionic liquids as green solvents to replace or minimize conventional environment-harming organic solvents. Ionic liquids have many remarkable environment-accepting properties such as ease of reuse, low vapour pressure, and thermal stability etc. The present work focuses on thermodynamic understanding of aqueous solutions of protic ionic liquids (PILs) namely triethylammonium formate [TEAF], triethylammonium propionate [TEAP], triethylammonium butanoate [TEAB], triethylammonium glycolate [TEAG], and triethylammonium pyruvate [TEAPy]. The density and speed of sound measurements for aqueous solutions of these PILs are reported at T=298.15K and the data were used to obtain the apparent and partial molar volumes, isentropic and apparent molar isentropic compressibilities for aqueous PILs solution. From the data of density and sound speed, we estimated electrostriction, hydration numbers of PILs, limiting volumetric and compressibility properties and finally discussed the results obtained in terms of ion-ion, ion-solvent interaction through hydration behaviour of PILs, kosmotropic effect, hydrophobic interactions, etc.

Isolating Protein Charge State Reduction in Electrospray Droplets Using Femtosecond Laser Vaporization.

Charge state distributions are measured using mass spectrometry for both native and denatured cytochrome c and myoglobin after laser vaporization from the solution state into an electrospray (ES) plume consisting of a series of solution additives differing in gas-phase basicity. The charge distribution depends on both the pH of the protein solution prior to laser vaporization and the gas-phase basicity of the solution additive employed in the ES solvent. Cytochrome c (myoglobin) prepared in solutions with pH of 7.0, 2.6, and 2.3 resulted in the average charge state distribution (Zavg) of 7.0 ± 0.1 (8.2 ± 0.1), 9.7 ± 0.2 (14.5 ± 0.3), and 11.6 ± 0.3 (16.4 ± 0.1), respectively, in ammonium formate ES solvent. The charge distribution shifted from higher charge states to lower charge states when the ES solvent contained amines additives with higher gas-phase basicity. In the case of triethyl ammonium formate, Zavg of cytochrome c (myoglobin) prepared in solutions with pH of 7.0, 2.6, and 2.3 decreased to 4.9 (5.7), 7.4 ± 0.2 (9.6 ± 0.3), and 7.9 ± 0.3 (9.8 ± 0.2), respectively. The detection of a charge state distribution corresponding to folded protein after laser vaporized, acid-denatured protein interacts with the ES solvent containing ammonium formate, ammonium acetate, triethyl ammonium formate, and triethyl ammonium acetate suggests that at least a part of protein population folds within the electrospray droplet on a millisecond timescale. Graphical Abstract ᅟ.

Reaction of 3-arylidenepropenoic acid derivatives with triethylamine and other amines; unexpected reductions and vinylogations

Exposure of ethyl 2-cyano-3-(2-methoxy-5-nitrophenyl)acrylate 1f to triethylamine in hot ethanol resulted in the formation of the dihydro derivative 2f and vinylogue 3f in high yields. Single crystal X-ray data are provided for 3f. Similar reactions were observed for various analogues. The reaction was studied changing aryl substituent, amines and solvents. Pyridyl, thienyl analogues were also examined. The study was extended to cyclic molecules incorporating such systems like thiazolidinedione 8, 3-cyanocoumarin 9 and 4-arylidene-isoquinoline-2,4-diones 11. The last group gave vinylogated products, 4-cinnamylidene-isoquinolinediones and 4-hydroxylated species. A few examples of arylidene derivatives from malononitrile, ethyl acetoacetate, acetyl acetone and ethyl methylsufonylacetate were investigated. Ethyl cinnamate and β-nitrostyrene were unaffected. The reaction is considered to be possibly radical mediated, since addition of free radical quencher suppressed the reaction. Contrary to the effects of thermal conditions, irradiation of 1f in ethanol at 254 and 365 nm gave complex mixtures. A few other interesting observations in this study are noted: vinylogation of 1f with acetaldehyde to 3f; formation of 3f from 1f by the treatment with triethylamine, palladium carbon and reduction of 1f to 2f by triethylammonium formate in DMF.

Hydricity of an Fe-H Species and Catalytic CO2 Hydrogenation.

Despite renewed interest in carbon dioxide (CO2) reduction chemistry, examples of homogeneous iron catalysts that hydrogenate CO2 are limited compared to their noble-metal counterparts. Knowledge of the thermodynamic properties of iron hydride complexes, including M-H hydricities (ΔGH(-)), could aid in the development of new iron-based catalysts. Here we present the experimentally determined hydricity of an iron hydride complex: (SiP(iPr)3)Fe(H2)(H), ΔGH(-) = 54.3 ± 0.9 kcal/mol [SiP(iPr)3 = [Si(o-C6H4PiPr2)3](-)]. We also explore the CO2 hydrogenation chemistry of a series of triphosphinoiron complexes, each with a distinct apical unit on the ligand chelate (Si(-), C(-), PhB(-), N, B). The silyliron (SiP(R)3)Fe (R = iPr and Ph) and boratoiron (PhBP(iPr)3)Fe (PhBP(iPr)3 = [PhB(CH2PiPr2)3](-)) systems, as well as the recently reported (CP(iPr)3)Fe (CP(iPr)3 = [C(o-C6H4PiPr2)3](-)), are also catalysts for CO2 hydrogenation in methanol and in the presence of triethylamine, generating methylformate and triethylammonium formate at up to 200 TON using (SiP(Ph)3)FeCl as the precatalyst. Under stoichiometric conditions, the iron hydride complexes of this series react with CO2 to give formate complexes. Finally, the proposed mechanism of the (SiP(iPr)3)-Fe system proceeds through a monohydride intermediate (SiP(iPr)3)Fe(H2)(H), in contrast to that of the known and highly active tetraphosphinoiron, (tetraphos)Fe (tetraphos = P(o-C6H4PPh2)3), CO2 hydrogenation catalyst.

Capillary and Coulombic Effects on the Gas Phase Structure of Electrosprayed Concanavalin A Ions and Its Clusters Cn+z(n= 1–6)

Ion mobility spectrometry (IMS) coupled to mass spectrometry (MS) is used to study the gas phase collision cross section Ω(z, n) in CO(2) of multimers C(n) (n = 1-4, 6) of concanavalin A, whose tetramer C(4) has a crystal structure resembling four tetrahedrically arranged globules. C(n)(+z) ions electrosprayed from aqueous solutions of triethylammonium formate (Et(3)AF) are moderately charged (up to z = 6 and 17 for n = 1 and 6) and produce narrow mobility peaks. Charge states down to z = 1 obtained with a charge-reducing radioactive (63)Ni source are studied for the dimer and the tetramer via pure IMS (no MS). The mobilities are independent of pH in the range 6-8, controlled by addition of triethylamine to the Et(3)AF. The measured compactness group Ω(z, n)/n(2/3) is practically independent of n and z, whereas mobility calculations with clusters of touching spheres show that it should vary with n by 20-30% for a variety of scattering models. This contrast suggests that, irrespective of ambiguities on the scattering model, all multimers adopt globular shapes, precluding in particular a tetrahedral tetramer. Acetic acid solutions (87 mM aqueous) yield ions with substantially higher z, mostly with broad mobility distributions. Exceptionally high z tetramers (z = 25-29) and trimers have narrowly defined mobilities with compact but nonspherical shapes. Addition of 2-4 mM Et(3)AF to the 87 mM aqueous acetic acid solution yields narrowly defined mobilities almost identical at all z values to those from the Et(3)AF buffer, although with higher charge states showing also a transition to nonspherical shapes. We conclude that all gas phase clusters charged below a Rayleigh-like charge, z(R), are globular without regard to solution conditions, some undergoing a sharp shape transition at a critical z = z(R). We confirm that gas phase protein cross sections differ from those expected from the crystal structure, with a trend to compact probably driven by their high surface energy (and opposed by Coulombic stresses). The Rayleigh-like shape transitions seen are similar to those arising in linear homopolymers, although not as sharply defined. They yield a surface energy for protein matter almost as high as the surface tension of water. This quantitative conclusion is corroborated by prior data on cytochrome c and apomyoglobin (also showing a critical shape transition) as well as measurements of the maximum charge versus mass in aggregates of dipeptides.

Synthesis of cyclic azobenzene analogues

Reaction of 2,2′-dinitrodibenzyl with lead metal powder in the presence of a basic triethylammonium formate buffer gave a cyclic azoxybenzene, 11,12-dihydrodibenzo[c,g][1,2]diazocine-5-oxide. The latter compound was converted into cyclic azobenzene and analogues (chloro-, bromo-, and cyano-) through subsequent transformations. Hydrolysis of the cyano cyclic azobenzene gave the corresponding carboxylic acid. This carboxylic acid was finally reacted with d-threoninol to give the corresponding amide, which readily undergoes photoisomerization upon illumination with light.

Enantioselective Synthesis of anti‐β‐Hydroxy‐α‐Amido Esters by Asymmetric Transfer Hydrogenation in Emulsions

Herein, we present two methods for an asymmetric transfer hydrogenation through the dynamic kinetic resolution of α-amido-β-ketoesters. These procedures yield the corresponding anti-β-hydroxy-α-amido esters in good yields and with good diastereo- and enantioselectivities. First, the scope of the reduction of α-amido-β-ketoesters by using triethylammonium formate azeotrope is examined. Then, an emulsion technology with sodium formate is explored, which allows for broader substrate scope, faster reaction times, and lower catalyst loading. Furthermore, these reactions are operationally simple and can be set up in air.

ChemInform Abstract: Short Synthesis of Ethyl 3‐(3‐Aminophenyl)propanoate (V).

AbstractThe title compound (V) is efficiently obtained using a tandem Knoevenagel condensation/alkylidene reduction of 3‐nitrobenzaldehyde with Meldrum′s acid in the presence of triethylammonium formate followed by reduction of the intermediate 3‐(3‐nitrophenyl)propanoic acid by stannous chloride.

Short Synthesis of Ethyl 3‐(3‐aminophenyl)propanoate

A short and effective synthesis of ethyl 3-(3-aminophenyl)propanoate is presented, employing a tandem Knoevenagel condensation/alkylidene reduction of 3-nitrobenzaldehyde with Meldrum's acid in TEAF (triethylammonium formate) followed by reduction of the intermediate 3-(3-nitrophenyl)propanoic acid by stannous chloride in ethanol. The use of stannous chloride as the reducing agent in ethanol enabled the simultaneous esterification of the carboxylic acid. Thus, stannous chloride was acting simultaneously as a Lewis acid, which activates the carboxylic acid towards a nucleophilic attack by ethanol.

Reductive dehalogenation of aryl halides over palladium catalysts deposited on SBA-15 type molecular sieve modified with amine donor groups

Supported palladium catalysts prepared from palladium(II) acetate and SBA-15 type molecular sieve modified with N-[2-(diethylamino)ethyl]-3-aminopropyl donor groups efficiently catalyse reductive dehalogenation of various bromo- and iodobenzenes with in situ formed triethylammonium formate as the hydrogen source. Since the corresponding chlorobenzenes react at considerably lower rates while fluorobenzenes remain unaffected, the catalytic system can be utilised for selective dehalogenations of multiply halogenated substrates. Compared with Pd/C tested earlier [N.A. Cortese, R.F. Heck, J. Org. Chem. 42 (1977) 3491], the catalysts deposited over modified SBA-15 are more reactive. Besides, they exert rather minor leaching of the metal component (8.4% during five consecutive runs with 0.5 mol.% Pd with respect to the substrate) and maintain their high activity during repeated use.

Effect of protic ionic liquids (PILs) on the formation of non-ionic dodecyl poly(ethylene oxide) surfactant self-assembly structures and the effect of these surfactants on the nanostructure of PILs

The ability of a series of non-ionic dodecyl poly(ethylene oxide) surfactants to form micelles in a variety of protic ionic liquids (PILs) was investigated using small and wide angle X-ray scattering (SAXS/WAXS). The C(12)E(n) surfactants with n = 3-8 were examined in PILs which contained either an ethyl, diethyl, triethyl, butyl, pentyl, ethanol or pentanol-ammonium cation in conjunction with either a nitrate or formate anion. The ability of the PILs to support micelles of these surfactants was highly dependent on their liquid nanostructure. The PILs containing hydroxyl groups on the cations were not nanostructured and had very low surfactant solubility (<1 wt%). The highly nanostructured PILs with butylammonium or pentylammonium cations contain large non-polar domains, and had excellent surfactant solubility, but due to the greater hydrocarbon solubility they had insufficient drive from the "solvophobic effect" to enable micelle formation. The PILs of ethylammonium nitrate (EAN), propylammonium nitrate (PAN), diethylammonium formate (DEAF) and triethylammonium formate (TEAF) had smaller non-polar domains, and all supported micelle formation below 20 wt% surfactant. The critical micelle concentration (CMC) of surfactants in EAN were two orders of magnitude greater than in water. The minimum molecular areas of the poly(ethylene oxide) head groups at the air/ionic liquid interface, A(min), were significantly larger in EAN than in water. The SAXS patterns from the micelles present in EAN fitted well to ellipsoids, whereas the micelles present in PAN fitted well to spheres. The nanostructure of select PILs was also influenced by the presence of surfactants.

Ion Mobility Measurements of Nondenatured 12–150 kDa Proteins and Protein Multimers by Tandem Differential Mobility Analysis–Mass Spectrometry (DMA-MS)

The mobilities of electrosprayed proteins and protein multimers with molecular weights ranging from 12.4 kDa (cytochrome C monomers) to 154 kDa (nonspecific concanavalin A hexamers) were measured in dry air by a planar differential mobility analyzer (DMA) coupled to a time-of-flight mass spectrometer (TOF-MS). The DMA determines true mobility at atmospheric pressure, without perturbing ion structure from that delivered by the electrospray. A nondenaturing aqueous 20 mM triethylammonium formate buffer yields compact ions with low charge states, moderating polarization effects on ion mobility. Conversion of mobilities into cross-sections involves a reduction factor ξ for the actual mobility relative to that associated with elastic specular collisions with smooth surfaces. ξ is known to be 1.36 in air from Millikan's oil drop experiments. A similar enhancement effect ascribed to atomic-scale surface roughness has been found in numerical simulations. Adopting Millikan's value ξ=1.36 and assuming a spherical geometry yields a gas-phase protein density ρ(p)=0.949±0.053 g cm(-3) for all our protein data. This is substantially higher than the 0.67 g cm(-3) found in recent low-resolution DMA measurements of singly charged proteins. DMA-MS can distinguish nonspecific protein aggregates formed during the electrospray process from those formed preferentially in solution. The observed charge versus diameter relation is compatible with a protein charge reduction mechanism based on the evaporation of triethylammonium ions from electrosprayed drops.

ChemInform Abstract: One‐Pot Conversion of Alkyl Aldehydes into Substituted Propanoic Acids via Knoevenagel Condensation with Meldrum′s Acid.

Abstract Reaction of a range of alkyl aldehydes and Meldrum’s acid in triethylammonium formate (TEAF) at 100 °C generates substituted propanoic acids in a single step.

Mechanism of Pd(NHC)-Catalyzed Transfer Hydrogenation of Alkynes

The transfer semihydrogenation of alkynes to (Z)-alkenes shows excellent chemo- and stereoselectivity when using a zerovalent palladium(NHC)(maleic anhydride)-complex as precatalyst and triethylammonium formate as hydrogen donor. Studies on the kinetics under reaction conditions showed a broken positive order in substrate and first order in catalyst and hydrogen donor. Deuterium-labeling studies on the hydrogen donor showed that both hydrogens of formic acid display a primary kinetic isotope effect, indicating that proton and hydride transfers are separate rate-determining steps. By monitoring the reaction with NMR, we observed the presence of a coordinated formate anion and found that part of the maleic anhydride remains coordinated during the reaction. From these observations, we propose a mechanism in which hydrogen transfer from coordinated formate anion to zerovalent palladium(NHC)(MA)(alkyne)-complex is followed by migratory insertion of hydride, after which the product alkene is liberated by proton transfer from the triethylammonium cation. The explanation for the high selectivity observed lies in the competition between strongly coordinating solvent and alkyne for a Pd(alkene)-intermediate.

One-pot conversion of alkyl aldehydes into substituted propanoic acids via Knoevenagel condensation with Meldrum’s acid

Reaction of a range of alkyl aldehydes and Meldrum’s acid in triethylammonium formate (TEAF) at 100 °C generates substituted propanoic acids in a single step.

ChemInform Abstract: The Birth and Development of π-Allylpalladium Chemistry

The reaction of π-allylpalladium chloride with malonate to give allylmalonate discovered in 1965 marked the birth of π-allylpalladium chemistry. A group of new synthetic reactions, developed subsequently in our laboratory based on Pd-catalyzed decarboxylation of allyl carbonates, allyl β-keto carboxylates, and allyl formates are summarized. All these reactions proceed under neutral conditions. Allyl carbonates are very active for allylation of nucleophiles without a base. A new generation of β- keto esters and malonates was developed by the introduction of the Pd-catalyzed reaction of their allylic esters. Hydrogenolysis of allylic compounds with triethylammonium formate proceeds regio- and stereoselectively to afford regio- and stereodefined olefins. The hydrogenolysis also can be used for deprotection of the allyl protecting group.