Excess Amine Research Articles

Luminescent complexes of iridium(iii) with aliphatic amines and detection of biogenic amines

The straightforward reaction of [Ir2(ppy)4(µ-Cl)2] with an excess of aliphatic amines yields luminescent iridium complexes of general formula [IrCl(ppy)2(amine)] [amine = n-octylamine (1), t-butylamine (2), piperidine (3)]. The higher sterical hindrance of the amine in complex 2 was the responsible of its equilibrium with the starting materials. The luminescence of 1 and 3 has been studied showing emission at 508 and 509 nm respectively. As the aliphatic amines can be considered models of biogenic amines, this luminescence has been used to explore the viability of this reaction in the detection of biogenic amines. The exposition to vapors of biogenic amines of a solution of [Ir2(ppy)4(µ-Cl)2] in CH2Cl2 or in different solid supports, showed that it was possible to detect the amines in a quick and easy way, with limits of detection value (in solution of methylene chloride) of 4.8 µM for cadaverine.

An Aminopyrrolidinyl Phosphonates—A New Class of Antibiotics: Facile Synthesis and Predicted Biological Activity

A novel class of aminopyrrolidinyl phosphonates was synthesized in 74% - 80% isolated yield by the addition of three-fold excess of primary amines to diethyl 4-chloro-1-butynylphosphonates. The reaction was carried out at room temperature and in the absence of solvent or catalyst to give solely compounds which showed predicted biological activity based on PASS program. Some of the synthesized derivatives of antibiotics exhibit properties for the treatment of stroke, the treatment of acute neurological disorders, and can also be acetyl esterase inhibitors.

Lyotropic liquid crystal phase behavior of a cationic amphiphile in aqueous and non-stoichiometric protic ionic liquid mixtures.

Protic ionic liquids (PILs) are the largest and most tailorable known class of non-aqueous solvents which possess the ability to support amphiphile self-assembly. However, little is known about the effect of solvent additives on this ability. In this study, the lyotropic liquid crystal phase (LLCP) behavior of the cationic surfactant cetyltrimethylammonium bromide (CTAB) was investigated in the model PILs of ethylammonium nitrate (EAN) and ethanolammonium nitrate (EtAN), and derived multi-component solvent systems containing them to determine phase formation and diversity with changing solvent composition. The solvent systems were composed of water, nitric acid and ethylamine (or ethanolamine), with 26 unique compositions for each PIL covering the apparent pH and ionicity ranges of 0-13.5 and 0-11 M, respectively. The LLCPs were studied using cross polarized optical microscopy (CPOM) and small and wide-angle X-ray scattering (SAXS/WAXS). Partial phase diagrams were constructed for CTAB concentrations of 50 wt% and 70 wt% in the temperature range of 25 °C to 75 °C to characterise the effect of surfactant concentration and temperature on the LLCPs in each solvent environment. Normal micellar (L1), hexagonal (H1) and bicontinuous cubic (V1) phases were identified at both surfactant concentrations, and from temperatures as low as 35 °C, with large variations dependent on the solvent composition. The thermal stability and diversity of phases were greater and broader in solvent compositions with excess precursor amines present compared to those in the neat PILs. In acid-rich solvent combinations, the same phase diversity was found, though with reduced onset temperatures of phase formation; however, some structural changes were observed which were attributed to oxidation/decomposition of CTAB in a nitric acid environment. This study showed that the ability of PIL solutions to support amphiphile self-assembly can readily be tuned, and that the ability of PILs to promote amphiphile self-assembly is robust, even with other solvent species present.

Spherical amine grafted silica aerogels for CO2 capture.

The objective of this research was to develop a novel spherical amine grafted silica aerogel for CO2 capture. A spherical silica gel was synthesized by dropping a sodium silicate based silica sol into an oil bath. Amine grafting was achieved by bonding 3-aminopropyltriethoxysilane onto the framework of the silica gel. The spherical amine grafted silica gels were dried using vacuum drying to prepare the spherical amine grafted silica aerogels (SASAs). The synthetic mechanism of the SASAs was proposed. The structures and the CO2 adsorption performances of SASAs were researched. The amine loading of the SASAs increased with the grafting time, however, the specific surface area and pore volume sharply decreased owing to the blockage of the pore space. Excess amine loading led to the decrease of the CO2 adsorption capacity. The optimal CO2 adsorption capacity was 1.56 mmol g−1 with dry 1% CO2 and at 35 °C. This work provides a low-cost and environmentally friendly way to design a capable and regenerable adsorbent material.

Spin-assisted interfacial polymerization strategy for graphene oxide-polyamide composite nanofiltration membrane with high performance

Graphene oxide (GO) has been addressed to have greatly potential in nanofiltration membranes. The state-of-the-art GO-based nanofiltration is still limited by the low permeability and instability for the large-scale industrial application. Herein, we developed a novel interfacial polymerization technology for high permeability and advanced stability GO-polyamide membrane with the help of spin. The high-rough microfiltration membrane was chosen as the substrate for providing large effective filtration area and trapping GO nanosheets in valley structures. Aided with centrifugal force field from the spin, the excess low concentration amine monomer solutioncould be removed homogeneous to form ultrathin and defect-free polyamide (PA) layer. The pure water permeability of the graphene oxide-polyamide (GO-PA) composite nanofiltration membrane could be up to 35.14 LMH/bar with Na2SO4 rejection of 93.56% at 4 bar, which is comparable to the top permeability of GO-based nanofiltration membranes with the similar salt rejection that has been reported. The membranes also behave high Na2SO4/NaCl selectivity (15–56) due to the extremely low NaCl rejection. In addition, the GO-PA composite nanofiltration membranes exhibit good stability in harsh environment and solvents. This work promotes GO-based nanofiltration for practical applications and provides a novel route for high-performance nanofiltration membranes.

Reactions of Ethyl 5-Methyl-4-(1,2,3-thiadiazol-4-yl)furan-2-carboxylate with Selected Bases

The reactions of 5-methyl-4-(1,2,3-thiadiazol-4-yl)furan-2-carboxylic acid ethyl ester with some bases have been studied. The opening of 1,2,3-thiadiazole ring under the action of potassium tert-butylate in tetrahydrofuran in the presence of methyl iodide has led to the corresponding 4-methylsulfanylethynylfuran derivative. Under the action of potassium carbonate in DMF with an excess of primary amines or morpholine, the starting thiadiazole has formed the corresponding thioamides of furylacetic acid. The reaction of ethyl 5-methyl-4-(1,2,3-thiadiazol-4-yl)furan-2-carboxylate with hydrazine hydrate has led to hydrazinolysis of the ester group without cleavage of the 1,2,3-thiadiazole ring.

Changing the kinetic order of enantiomer formation and distinguishing between iminium ion and imine as the reactive species in the asymmetric transfer hydrogenation of substituted imines using a cyclopentadienyl iridium (III) complex

Abstract The iridium (III) complex of pentamethylcyclopentadiene and (S,S) or (R,R)-1,2-diphenyl-N′-tosylethane-1,2-diamine is an effective catalyst for the asymmetric transfer hydrogenation of imines under acidic conditions. However, the enantiomeric excess (ee) of the product amines from the reduction of 1-methyl-3,4-dihydroisoquinolines in either acetonitrile or dichloromethane, decreases exponentially. The dominant cause of the enantioselectivity is the difference in kinetic order of the formation of the two enantiomers with the S-enantiomer being formed in a first-order process whereas that for the R-enantiomer follows zero-order kinetics when (R,R)-TsDPEN is employed, due to different rate-limiting steps for the two processes. A series of 1-fluorinated methyl-3,4-dihydroisoquinolines were synthesised to change the rate-limiting dissociation of the (R) amine product from Ir (III) so that both enantiomers are formed with the same kinetic order. This results in almost complete removal of the enantioselectivity of the reduction. It has been suggested that reduction of imines using transition metal complexes occurs through the neutral imine rather than the more reactive iminium-ion. α-Substituted imines with electron-withdrawing groups make protonation more difficult but enhance the electrophilicity of the imine carbon facilitating nucleophilic attack. The pK a of the iminium ions of 1-fluorinated methyl-3,4-dihydroisoquinolines were determined. Using the relative rates of the cyclopentadienyl iridium (III) complex catalysed reduction of these 1-fluorinated methyl-3,4-dihydroisoquinoline in acetonitrile and, under the acidic conditions of a 5:2 ratio of formic acid:triethylamine, showed that the iminium ion is the reactive species.

Thermal analysis of salts from 4-nitrophenol and aliphatic amines

Solid samples obtained from 4-nitrophenol and aliphatic amines, in excess of amine, were submitted to thermal analysis. The TGA/DTA showed two endothermic events, with exception of tert-butylamine, which showed three endothermic peaks. The first event was the melting of the ionic salt, which temperature does not follow a pattern, and is maxim for ethylammonium minimal for butylammonium salt. For methylammonium and ethylammonium, the fusion is followed by mass loss corresponding to one amine by 4-nitrophenol, while for the others ammonium salts, this event marks the beginning of the mass variation, that is maintained until the decomposition of the 4-nitrophenol at 485 K. The temperature of the event depends of the length of the chain of the amine, while the second occurs at the same temperature for all amines.

Promising approaches to improve the performances of hybrid non‐isocyanate polyurethane

AbstractThe performances of hybrid non‐isocyanate polyurethane (NIPU) materials were improved by using promising approaches. For the ring‐opening reaction of cyclic carbonate with excess amine, methanol was selected as solvent to increase the molar mass of NH2‐terminated NIPU pre‐polymer but also caused the formation of urea as a result of eliminating hydrogen bonding between NIPU chains. Meanwhile, another approach was carried out to reduce the content of urea by altering the introduction mode of reactants, along with further increasing the molar mass of the NIPU pre‐polymer. The final hybrid materials were prepared by adding bisphenol‐A diglycidyl ether into the pre‐polymer. The results indicated that the introduction of methanol and the change of the introduction mode of reactants could improve the performance of the hybrid materials. The hybrid material derived from the forward method has optimal performance with a tensile strength of 10.8 MPa, elongation at break of 167%, a glass transition temperature of 49.1 °C and a crosslinking density of 450 mol m−3 as well as presentable thermodynamic stability, ascribed to the high molar mass of the NIPU pre‐polymer, the low urea content and the dense crosslinking network. © 2018 Society of Chemical Industry

Dynamic covalent Schiff-base silicone polymers and elastomers

Polymers with dynamically exchanging crosslinks possess the ability to be repurposed, in whole or part, following a stimulus. The ability of imines to undergo dynamic exchange reactions under mild conditions was utilized to chain extend or crosslink silicone polymers. Schiff-base crosslinked polysiloxanes were prepared by reacting aminopropyl-functionalized polydimethylsiloxane with aromatic aldehydes. The reactions occur efficiently and the water byproduct spontaneously separates from the silicone if the weight fraction of silicone is sufficiently high. The physical properties of the products were readily tunable by crosslink density; the most practical reaction partners were commercial pendant aminopropylsilicones with terephthaldehyde, although telechelic silicones and triformylbenzene were also utilized. Complete breakdown of the polymers occurred with addition of excess amine. Silicone imine cleavage with excess aldehyde also occurred, but the two processes followed different pathways. The rate of the dynamic processes was increased with good solvents, or acid or amine catalysts. However, even in the absence of catalysts the dynamic transimination was efficient. Simply placing two strips of the elastomer in contact led to an adhesive bond that, depending on contact surface area, was stronger than the cohesive strength of the rubber. The process of self-healing was followed using rheology and was shown to be complete within an hour. Surface modification of elastomers with amines occurred in water, or at aminated solid surfaces.

Complete Generation of a 129Xe Biosensor on the Solid Support by Systematic Backbone Assembly.

Xenon biosensors are an emerging tool for different molecular imaging approaches. For many applications, their development requires peptide synthesis steps, followed by the selective installation of a xenon host onto the peptide backbone in solution. In this study, three different strategies were attempted for generating entire Xe biosensors on the solid support. Notably, one strategy involving CryA-da was beneficial by directly integrating this host into the growing construct on a low loaded resin via modification of the administered subcomponent equivalents and by prolonging the coupling procedure. Subsequently, installation of additional amino acids or of additional labels onto the growing construct was achieved by a procedure in which an excess amine was administered to the activated CryA-da (acid) anchored onto the resin. Further, the as-generated Xe biosensor was tested for its NMR and MRI capabilities in H2O and compared to the performance of CryA-ma. Xe NMR of the biosensor indicated a clear CEST response and the Xe MR images revealed similar contrast compared to the reference host. These observations suggest that functionalizing CryA-da on both sides with multiple labels did not alter significantly its NMR capabilities. Hereby, we could show the successful and complete synthesis of a CryA-da-based xenon biosensor on the solid support without any notable side reactions and without the necessity of multiple purification steps.

One-pot α-ferrocenylalkylation of amines and alcohols with α-ferrocenyl substituted alcohols under acid-free conditions

One-pot reaction of FcCH(R)OH with equimolar quantities of BunLi and EtOCOCl followed by an excess of amine produces N-(α-ferrocenylalkyl)amines in up to 98% yields. Nitrogen heteroaryl amines undergo the α-ferrocenylalkylation at the amino group. The α-ferrocenylalkylation of alcohols and phenols (R’OH) leads to a formation of ethers FcCH(R)OR′ in lower yields. The reactions proceed via an intermediate formation of α-ferrocenylalkyl carbonates FcCH(R)OCOOEt. The side reactions associated with this protocol are discussed.

Heterogeneous amino-functionalized particles boost hydrogen production from Formic Acid by a ruthenium complex

Silica Amino –Functionalized H2N@SiO2 nanoparticles are shown to boost by >700% the TONs of H2 production by the [Ru/P(CH2CH2PPh2)3] homogeneous catalyst, using Formic Acid (FA) as substrate. Thermodynamic analysis reveals that a significant decrease of the activation energy from Ea = 41±9 kJ/mol to Ea = 28±5 kJ/mol occurs when the H2N@SiO2 solid material is used as cocatlasyt vs. the corresponding propylamine in homogeneous phase. The molecular basis of this thermodynamic mechanism was traced using EPR and variable-Temperature UV–Vis spectroscopy. It is shown that H2N@SiO2 particles play a dual role: [i] they act as cocatalyst, and [ii] they serve as a template which assembles the [Ru/P(CH2CH2PPh2)3] catalyst on its surface, thus promoting rapid formate decomposition via [RuII-hydride] species. Moreover we exemplify, for the first time, that the use of heterogenised H2N@SiO2 cocatalyst alleviates the –so far required-need of excess of amines as additives i.e. a ratio [amine (H2N@SiO2): Ru complex] = [1:1] is adequate to promote high TONs, instead of [50:1] typically needed for liquid amines.

Improved CO2 Sorption in Freeze-Dried Amine Functionalized Mesoporous Silica Sorbent

This work investigates the structural and CO2 sorption properties of amine-functionalized mesoporous silica prepared by a freeze-drying method. It was found that the freeze-dried samples delivered significantly higher CO2 sorption capacities up to a factor of 18 times as compared to samples prepared by the conventional oven-drying evaporation method. The improved performance of the freeze-drying method was attributed to a higher surface area and access to active amine sites for CO2 sorption. The freeze-dried samples also exhibited good stability at a relatively high sorption temperature (90 °C) and flue gas CO2 partial pressure (15 kPa). The freeze-drying method reached the best CO2 sorption capacity of 4.71 mmol g–1 for samples with 70 wt % amine loading. Higher loading (80 and 90 wt %) led to excess amine not being incorporated into the mesoporous silica structure, thus covering active sites and limiting CO2 diffusion.

Green Synthesis of 1,4‐Dihydropyridine Derivative in Water

AbstractA simple and environmentally clean synthesis of 4‐methoxycarbonylmethyl‐1,4‐dihydropyridine‐3,5‐dicarboxylic acid dimethyl ester was achieved by heating methyl propiolate with an amine salt in water. Excess amine salt accelerated the reaction in the case of aliphatic amines, while stoichiometric amounts of propiolate ester and amine salt resulted in low yield. In the case of aniline, a 1:3 ratio of amine salt and methyl propiolate afforded 77% yield in 24 h. The free amine is proposed to serve as nucleophile for Michael addition reaction, and the liberated proton acts as an electrophilic catalyst.

Quantum chemical study of the impact of protective association on the chemoselective synthesis of carboxybetaine from 2-(dimethylamino)ethanol and acrylic acid

Abstract Targeted carboxybetaine synthesis is an important process that one can apply to prepare polymeric materials with various unique properties or low molecular weight products, such as deep eutectic solvents based on acrylic acid formulated for the specific tasks. Analyzing the mechanism of carboxybetaine formation, it was found that with an excess of amine, the H-bond formed between amine nitrogen and the acidic proton of the acrylic acid was strong enough to protect the intermediate obtained after carbanion protonation from the interaction with acrylate anion, thus facilitating the formation of quaternary ammonium salts as the final product at the beginning of the reaction instead of the desired carboxybetaine. Similarly, a threefold excess of acrylic acid should also lead to the preferential formation of the quaternary salt due to the protection of the half-product from the interaction with acrylate anion via cyclic dimer formation with two strong H-bonds. From the other side, calculations revealed that a twofold excess of acrylic acid should provide formation of carboxybetaine as the dominant product. The discussed energy profiles were supplemented with extensive natural bond order analysis in the course of which delocalization energies were calculated and used to discuss the strength of intermolecular donor–acceptor interactions within the considered molecular systems.

Water Chemistry and Chemistry Monitoring at Thermal and Nuclear Power Plants: Problems and Tasks (Based on Proceedings of Conferences)

In late May–early June 2017, two international science and technology conferences on problems of water chemistry and chemistry monitoring at thermal and nuclear power plants were held. The participants of both the first conference held at OAO VTI and the second conference that took place at NITI formulated the problems of the development of the regulatory base and implementation of promising water treatment technologies and outlined the ways of improving the water chemistry and chemistry monitoring at TPPs and NPPs for the near future. It was pointed out that the new amine-containing VTIAMIN agent developed by OAO VTI had been successfully tested on the power-generating units equipped with steam–gas plants to establish the minimum excess of the film-forming amine in the power-generating unit circuit that ensures the protection of the metal as 5–10 μg/dm3. A flow-injection technique for the analysis of trace concentrations of chlorides was proposed; the technique applied to the condensate of the 1000-MW steam turbine of the NPP power-generating unit yields the results comparable with the results obtained by the ion chromatography and the potentiometric method using the solver electrode. The participants of the conferences were demonstrated new Russian instruments to analyze the water media at the TPPs and NPPs, including the total organic carbon analyzer and the analyzer of mineral impurities in the condensate and feed water, that won a gold medal at the 45th International Exhibition of Inventions held in Geneva this April.

Synthesis of 6H-isoindolo[2,1-a]indol-6-ones via Pd-catalyzed cycloaminocarbonylation of 2-(1H-indol-2-yl)phenyl tosylates with CO

An efficient method for preparation of substituted 6H-isoindolo[2,1-a]indol-6-ones (2) that are important structural components of a vast array of naturally occurring and pharmacologically active compounds, has been developed by the palladium-catalyzed intramolecular cycloaminocarbonylation of 2-(1H-indol-2-yl)phenyl tosylates with CO. Significantly, the intermolecular aminocarbonylation products 2-(1H-indol-2-yl)benzamides are formed when an excess of amine is used in this reaction system. Alternatively, 2-(1H-indol-2-yl)benzamides can also be synthesized by the in situ aminolysis of 2. Furthermore, treatment of 2 with hydrosilane in the presence of KOH gave the unprecedented reducing products 2-(-1H-indol-2-yl)benzyl alcohols in 75–86% yields. These results demonstrate that 6H-isoindolo[2,1-a]indol-6-ones are versatile substrates for further synthetic elaboration.

Synthesis, physical and chemical properties of 7-methylxanthine derivatives

It is known that 8-aminosubstituted N-methylated xanthines are dipeptidyl peptidase-4 antagonists, ligands for 5-hydroxytryptamine receptors and exert diverse biological effects. Previously, it was found that the 7-alkyl-8-piperazinoxanthines exhibit diuretic, depremic, analgesic effect. Some amino derivatives of 7-metilxanthine are promising antioxidants and 8-amino-7-ethyl-3-methylxanthine detects a distinct hypoglycemic effect. The aim of this work is to provide new derivatives of 7-methylxanthine – promising bioactive compounds and to study their physical and chemical properties as a basis for further structural modification of the molecule. Materials and methods . The melting point has been determined with the help of an open capillary method with PTP-M device. Elemental analysis has been performed with the help of the instrument Elementar Vario L cube, NMR-spectra have been taken on a spectrometer Bruker SF-400 (operating frequency of 400 MHz, solvent DMSO, internal standard – TMS). Results . It is established that the heating the source of bromxantine with an excess of primary amines in a mixture of water and dioxane leads to the formation of the corresponding 8-aminosubstituted 7-ethyl-3-methylxanthine. The reaction of 8-bromo-7-ethyl-3-methylxanthine and 8-bromo-7-ethyltheophylline with the more nucleophilic N-substituted piperazine is performed in the same conditions, but requires much less time and is accompanied by the formation of the corresponding 8-N-piperazinxanthines. Taking into account the amphoteric properties of imidazole it was possible to obtain 7-ethyl-8-(midazol-1)-3-methylxanthine through the reaction in dimethylformamide in the presence of equimolar amount of NaHCO 3 . 8-(4-Tret- butoxycarbonylaminopiperidinyl-1)-7-ethyl-3-methylxanthine and 8-(4-tret-butoxycarbonylamino-1)-7-ethyltheophylline are obtained by heating equimolar amounts of original bromxanthines, 4-tret-butoxycarbonylaminopiperidine and NaHCO 3 . The structure of the synthesized compounds is unambiguously proved by the method of NMR spectroscopy. The synthesized compounds are white crystalline substances soluble in hot alcohols, dioxane, DMF. The fact that 8-N,N-diethylamino-7-ethyl-3-methylxanthine and 7-ethyl-8-(midazol-1)-3-methylxanthine are well soluble in diluted acid solutions, can be used to obtain new bioactive salts with organic and inorganic acids. The presence of free N 1 H group enables the synthesis of new 1,3,7,8-tetrasubstituted of xanthine by the introduction of a variety of electrophilic reagents into the position of 1 uracil part of the molecule. Conclusions . Simply implemented methods for the synthesis of 8-amino-7-methylxanthine are developed. NMR-spectroscopic study of the obtained compounds, which clearly confirms their structure, is conducted. The prospective of the synthesized compounds for subsequent modification of their structure is demonstrated.

Synthesis of hybrid polyhydroxyurethanes by Michael addition

The H-NIPU oligomers technology gives access to isocyanate-free polyurethanes mixing properties and reactivity of different reactants. The new hybrid H-NIPU materials were synthetized from PolyHydroxyUrethane (PHU) prepolymers terminated amines and acrylates compounds. To terminate the oligomers by amine with different chain length the cyclic carbonate (PPOBC640) was reacted with different excess of diamine (EDR-148 or CBMA). This excess of amine acts as a reactive diluent decreasing likewise the viscosity. Then, these aminotelechelic PHU oligomers were cross-linked at room temperature without solvent and catalyst thanks trimethylolpropane tris-acrylate (TMPTA) and different length of chain of poly(propylene oxide) bis-acrylate (PPOBGA). Different H-NIPU materials were obtained from a wide range oligomer of different molar masses and acrylates cross-linkers leading to new hybrid non-isocyanate polyurethane networks with various properties.