Conversion Of Amines Research Articles

The relationship between the pH value of dilute effluent streams and system durability in the separate bed electrodeionization process

The successful application of electrodeionization (EDI) for the preparation of ultra-pure water has been encouraging researchers to explore its feasibility in the treatment of heavy metal electroplating wastewaters. Based on the separate bed membrane stack, the relationship between the pH of dilute effluent streams and its long-term operation stability was investigated. The pH, conductivity, electric current and voltage were recorded on-line with cupric ions contents measured off-line. The microstructure and morphology of ion exchange resins and membranes were studied with infrared spectroscopy and scanning electron microscopy. It is the adsorption saturation in the cation exchange resins-filled compartment (CR-cell) that results in the acidity of dilute effluent waters due to the consumption of hydroxide ions in the anion exchange resins-filled compartment (AR-cell). The periodic change of acidity and alkalinity of dilute effluents was caused by the alternative processes of adsorption saturation and hydrolysis regeneration in CR-cell. The conversion of quaternary amines into tertiary ones of the anion resins and membranes owing to hygro-thermal aging weakened alkaline and shortened the acid-base change period. Increasing stack voltage and intermittent leaching play an important role in prolonging the service life of EDI, and make it feasible to remove heavy metal ions from industrial wastewaters.

2D sp2Carbon‐Conjugated Porphyrin Covalent Organic Framework for Cooperative Photocatalysis with TEMPO

Abstract2D covalent organic frameworks (COFs) are receiving ongoing attention in semiconductor photocatalysis. Herein, we present a photocatalytic selective chemical transformation by combining sp2carbon‐conjugated porphyrin‐based covalent organic framework (Por‐sp2c‐COF) photocatalysis with TEMPO catalysis illuminated by 623 nm red light‐emitting diodes (LEDs). Highly selective conversion of amines into imines was swiftly afforded in minutes. Specifically, the π‐conjugation of porphyrin linker leads to extensive absorption of red light; the sp2−C=C− double bonds linkage ensures the stability of Por‐sp2c‐COF under high concentrations of amine. Most importantly, we found that crystalline framework of Por‐sp2c‐COF is pivotal for cooperative photocatalysis with (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO). This work foreshadows that the outstanding hallmarks of COFs, particularly crystallinity, could be exploited to address energy and environmental challenges by cooperative photocatalysis.

2D sp2 Carbon-Conjugated Porphyrin Covalent Organic Framework for Cooperative Photocatalysis with TEMPO.

2D covalent organic frameworks (COFs) are receiving ongoing attention in semiconductor photocatalysis. Herein, we present a photocatalytic selective chemical transformation by combining sp2 carbon-conjugated porphyrin-based covalent organic framework (Por-sp2 c-COF) photocatalysis with TEMPO catalysis illuminated by 623 nm red light-emitting diodes (LEDs). Highly selective conversion of amines into imines was swiftly afforded in minutes. Specifically, the π-conjugation of porphyrin linker leads to extensive absorption of red light; the sp2 -C=C- double bonds linkage ensures the stability of Por-sp2 c-COF under high concentrations of amine. Most importantly, we found that crystalline framework of Por-sp2 c-COF is pivotal for cooperative photocatalysis with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO). This work foreshadows that the outstanding hallmarks of COFs, particularly crystallinity, could be exploited to address energy and environmental challenges by cooperative photocatalysis.

Highly Efficient Conversion of Propargylic Amines and CO2 Catalyzed by Noble-Metal-Free [Zn116 ] Nanocages.

The reaction of propargylic amines and CO2 can provide high-value-added chemical products. However, most of catalysts in such reactions employ noble metals to obtain high yield, and it is important to seek eco-friendly noble-metal-free MOFs catalysts. Here, a giant and lantern-like [Zn116 ] nanocage in zinc-tetrazole 3D framework [Zn22 (Trz)8 (OH)12 (H2 O)9 ⋅8 H2 O]n Trz=(C4 N12 O)4- (1) was obtained and structurally characterized. It consists of six [Zn14 O21 ] clusters and eight [Zn4 O4 ] clusters. To our knowledge, this is the highest-nuclearity nanocages constructed by Zn-clusters as building blocks to date. Importantly, catalytic investigations reveal that 1 can efficiently catalyze the cycloaddition of propargylic amines with CO2 , exclusively affording various 2-oxazolidinones under mild conditions. It is the first eco-friendly noble-metal-free MOFs catalyst for the cyclization of propargylic amines with CO2 . DFT calculations uncover that ZnII ions can efficiently activate both C≡C bonds of propargylic amines and CO2 by coordination interaction. NMR and FTIR spectroscopy further prove that Zn-clusters play an important role in activating C≡C bonds of propargylic amines. Furthermore, the electronic properties of related reactants, intermediates and products can help to understand the basic reaction mechanism and crucial role of catalyst 1.

Highly Efficient Conversion of Propargylic Amines and CO2 Catalyzed by Noble‐Metal‐Free [Zn116] Nanocages

AbstractThe reaction of propargylic amines and CO2 can provide high‐value‐added chemical products. However, most of catalysts in such reactions employ noble metals to obtain high yield, and it is important to seek eco‐friendly noble‐metal‐free MOFs catalysts. Here, a giant and lantern‐like [Zn116] nanocage in zinc‐tetrazole 3D framework [Zn22(Trz)8(OH)12(H2O)9⋅8 H2O]n Trz=(C4N12O)4− (1) was obtained and structurally characterized. It consists of six [Zn14O21] clusters and eight [Zn4O4] clusters. To our knowledge, this is the highest‐nuclearity nanocages constructed by Zn‐clusters as building blocks to date. Importantly, catalytic investigations reveal that 1 can efficiently catalyze the cycloaddition of propargylic amines with CO2, exclusively affording various 2‐oxazolidinones under mild conditions. It is the first eco‐friendly noble‐metal‐free MOFs catalyst for the cyclization of propargylic amines with CO2. DFT calculations uncover that ZnII ions can efficiently activate both C≡C bonds of propargylic amines and CO2 by coordination interaction. NMR and FTIR spectroscopy further prove that Zn‐clusters play an important role in activating C≡C bonds of propargylic amines. Furthermore, the electronic properties of related reactants, intermediates and products can help to understand the basic reaction mechanism and crucial role of catalyst 1.

Highly Efficient Photocatalytic Conversion of Amine to Amide and Degradation of Methylene Blue Using BiOCl–TiO2 Nano Heterostructures

Facile green synthesis of BiOCl–TiO2 was done using combustion technique by Ixora coccinea leaf extract as fuel source. The said material was characterized using XRD, SEM, EDX, HRTEM, SAED, FTIR, and UV-DRS. The particle size was found to be approximately 60 nm and a crystallite size of 0.3 nm from TEM. The photocatalytic activity of the material was found out using photoluminescence studies, dye degradation and photocatalytic organic conversion. The material showed excellent dye degradation capacity for methylene blue with 80% of the dye degraded under 3 hrs. The stabilisation of electron–hole pair by the heterostructure gave it the ability to perform easy degradation. The degradation kinetics have also been studied. It also showed an excellent organic conversion property with formylation yield reaching up to 96% and total conversion of the reactant molecule. The material is a potent photocatalyst due to its great efficiency and can have a remarkable role in the synthesis of important organic molecules and detoxification of environment. The heterostructure catalyses the conversion of amine to amides and mineralizes methylene blue under visible light condition.

Fragment-oriented synthesis: β-elaboration of cyclic amine fragments using enecarbamates as platform intermediates.

A strategy for the β-sp3 functionalisation of cyclic amines is described. Regioselective conversion of protected amines to enecarbamates is achieved through electrochemical oxidation; these intermediates can be derivatised by functionalised alkyl halides under photoredox catalysis. The potential of the methods is highlighted by direct growth of a DCP2B-binding fragment.

Estimation and Removal of Hazardous Aromatic Amines by the Oxidation with NaIO4 Spectrophotometrically : A Review

Many aromatic amines are the toxic in nature and impact a harmful effect in the body. Conversion of such carcinogenic aromatic amines in to other non carcinogenic compound by the oxidation process through sodium meta periodate is a good attempt in this way. Spectrophotometric method have been used for achieve the optimum condition and the estimation of aromatic amines.

Metal promoted conversion of aromatic amines to ortho-phenylenediimine derivatives by a radical coupling path.

A radical path for the conversion of o-substituted arylamines to o-phenylenediimine derivatives is reported. In the presence of [RuII(PPh3)3Cl2] (RuP), 2-(phenylthio)aniline (LSNH2) acts as an o-amination agent. Reaction of LSNH2 with RuP in toluene promotes (4e + 4H+) oxidative dimerization affording an o-phenylenediimine complex of ruthenium(ii). Similarly, intermolecular coupling between LSNH2 and other arylamines has been achieved.

Synthesis of tri‐aryl ketone amine isomers and their cure with epoxy resins

Isomeric tri‐aryl ketone amines, 1,3‐bis(3‐aminobenzoyl)benzene (133 BABB), 1,3‐bis(4‐aminobenzoyl)benzene (134 BABB), and 1,4‐bis(4‐aminobenzoyl)benzene (144 BABB) are synthesized and cured with diglycidyl ether of bisphenol A and diglycidyl ether of bisphenol F in this work. Differential scanning calorimetry and near‐infrared spectroscopy reveal higher rate constants and enhanced secondary amine conversion with increasing para substitution attributed to resonance effects and the electron withdrawing nature of the carbonyl linkages. Glass transition temperatures increase from 133 BABB to 134 BABB, but decrease modestly for the 144 BABB hardener. With increasing para substitution, the flexural modulus and strength both decrease while the strain to failure increases but all BABB amines displaying higher mechanical properties than the corresponding 4,4‐diaminodiphenyl sulfone (44 DDS) networks. The thermal stability of the BABB networks is found to be modestly lower than 44 DDS, but char yields are significantly higher. Changes in thermal and mechanical properties are described in terms of molecular structure and equilibrium packing density.

Direct Catalytic Decarboxylative Amination of Aryl Acetic Acids

AbstractThe decarboxylative coupling of a carboxylic acid with an amine nucleophile provides an alternative to the substitution of traditional organohalide coupling partners. Benzoic and alkynyl acids may be directly aminated by oxidative catalysis. In contrast, methods for intermolecular alkyl carboxylic acid to amine conversion, including amidate rearrangements and photoredox‐promoted approaches, require stoichiometric activation of the acid unit to generate isocyanate or radical intermediates. Reported here is a process for the direct chemoselective decarboxylative amination of electron‐poor arylacetates by oxidative Cu catalysis. The reaction proceeds at (or near) room temperature, uses native carboxylic acid starting materials, and is compatible with protic, electrophilic, and other potentially complicating functionality. Mechanistic studies support a pathway in which ionic decarboxylation of the acid generates a benzylic nucleophile which is aminated in a Chan–Evans–Lam‐type process.

Direct Catalytic Decarboxylative Amination of Aryl Acetic Acids.

The decarboxylative coupling of a carboxylic acid with an amine nucleophile provides an alternative to the substitution of traditional organohalide coupling partners. Benzoic and alkynyl acids may be directly aminated by oxidative catalysis. In contrast, methods for intermolecular alkyl carboxylic acid to amine conversion, including amidate rearrangements and photoredox-promoted approaches, require stoichiometric activation of the acid unit to generate isocyanate or radical intermediates. Reported here is a process for the direct chemoselective decarboxylative amination of electron-poor arylacetates by oxidative Cu catalysis. The reaction proceeds at (or near) room temperature, uses native carboxylic acid starting materials, and is compatible with protic, electrophilic, and other potentially complicating functionality. Mechanistic studies support a pathway in which ionic decarboxylation of the acid generates a benzylic nucleophile which is aminated in a Chan-Evans-Lam-type process.

Porous Anodic Aluminum Oxide as an Efficient Support for Ruthenium-Catalyzed Aerobic Oxidation of Alcohols and Amines

The oxidation reactions of alcohols and amines to their respective aldehydes/ketones and nitriles are important reactions in the laboratory and industry. A highly robust and activated ruthenium-supported anodic aluminum oxide (Ru@AAO) has been synthesized through the sonochemical method. The sonochemical technique allowed a short synthesis time and uniform distribution of Ru on the AAO surface as confirmed by the scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and BET surface-area analysis. The synthesized catalyst was employed for the oxidation of alcohols and amines in the presence of atmospheric air at a relatively lower temperature. The synthesized catalyst showed excellent conversions of both alcohols and amines with high selectivities toward their respective aldehydes/ketones and nitriles. The function of the AAO support in Ru@AAO catalytic activity has also been elaborated in the present investigation.

Graphene oxide-catalyzed two-step continuous-flow conversion of aryl amine to unsymmetrical thioether

A sustainable continuous-flow protocol for the conversion of aryl amine to unsymmetrical thioether is described. This technique is a two-step process involving graphene oxide (GO) catalyzed diazotization followed by the reaction with aryl/alkyl thiols. The continuous-flow conditions afford the desired thioethers in very good yields, effectively suppressing formation of possible disulfide, a common by-product in conventional process. The flow reaction is carried out under ambient conditions, applied to a variety of aryl amines and aryl/alkyl thiols and found to be scalable. The catalytic activity of the GO bed under continuous-flow conditions is found within standard time range and recyclable for ten consecutive runs without any loss of its performance.

Alkyl-functionalization of (3-Aminopropyl)triethoxysilane-grafted zeolite beta for carbon dioxide capture in temperature swing adsorption

Amine-based solid sorbents are promising candidates for post-combustion CO2 capture owing to their high sorption capacity at operating temperatures. Sorbents are required for stable CO2 mixture sorption and regeneration. Herein, we report a novel alkyl-functionalization method for the stoichiometric conversion of primary amines to secondary amines in solid sorbents. (3-Aminopropyl)triethoxysilane (APTES) and alkyl-functionalized-APTES were grafted on zeolite beta through a reflux reaction; the alkyl-functionalization was confirmed by nuclear magnetic resonance and Fourier transform infrared analyses. Alkyl-functionalized-APTES zeolite exhibited a sorption capacity of 1.44 mmol/g (15% CO2 balanced with N2 at 90 °C), very high sorption rate of t1/2 = 0.69 min (over 90% of the total sorption capacity within 5 min), and long-term stability after 20 cycles in a temperature swing adsorption (TSA) operation (above 0.9 mmol/g at pure CO2 regeneration). Alkyl-functionalized-APTES zeolite beta showed higher sorption capacity and stability than APTES zeolite and PEI silica in TSA operation at CO2 mixture sorption and CO2 flow regeneration.

In Vitro and In Vivo One-Pot Deracemization of Chiral Amines by Reaction Pathway Control of Enantiocomplementary ω-Transaminases

Biocatalytic cascade conversion of racemic amines into optically pure ones using enantiocomplementary ω-transaminases (ω-TAs) has been developed by thermodynamic and kinetic control of reaction pat...

Triazolopeptides Inhibiting the Interaction between Neuropilin-1 and Vascular Endothelial Growth Factor-165.

Inhibiting the interaction of neuropilin-1 (NRP-1) with vascular endothelial growth factor (VEGF) has become an interesting mechanism for potential anticancer therapies. In our previous works, we have obtained several submicromolar inhibitors of this interaction, including branched pentapeptides of general structure Lys(Har)-Xxx-Xxx-Arg. With the intent to improve the proteolytic stability of our inhibitors, we turned our attention to 1,4-disubstituted 1,2,3-triazoles as peptide bond isosteres. In the present contribution, we report the synthesis of 23 novel triazolopeptides along with their inhibitory activity. The compounds were synthesized using typical peptide chemistry methods, but with a conversion of amine into azide completely on solid support. The inhibitory activity of the synthesized derivatives spans from 9.2% to 58.1% at 10 μM concentration (the best compound Lys(Har)-GlyΨ[Trl]GlyΨ[Trl]Arg, 3, IC50 = 8.39 μM). Synthesized peptidotriazoles were tested for stability in human plasma and showed remarkable resistance toward proteolysis, with half-life times far exceeding 48 h. In vitro cell survival test resulted in no significant impact on bone marrow derived murine cells 32D viability. By means of molecular dynamics, we were able to propose a binding mode for compound 3 and discuss the observed structure–activity relationships.

Aerobic CuCl2-Catalyzed Dehydrogenative Cross-Coupling of Tertiary Amines. A Combined Computational and Experimental Study.

The generation of an iminium from amines is a way to functionalize the α carbon by coupling reactions. The reaction mechanism of the conversion of tertiary amines to iminium with CuCl2(H2O)2 as catalyst in aerobic conditions has been computationally and experimentally studied in this work. This process is initiated by the oxidation of the amine to a radical cation dichlorocuprate through the reduction of CuII to CuI. Then, the iminium dichlorocuprate is generated from the radical-ion through a hydrogen-transfer. The H atom can be accepted by molecular oxygen or by a second molecule of catalyst (in anaerobic conditions). Therefore, O2 also assumes the important role of acceptor along with that of regenerator of the catalyst. The experimental study confirmed the computational study and lead to the synthesis of four new molecules from the cross-coupling of N, N-diethyl- and N, N-diisoproylaniline with nitromethane and dimethylmalonate.

Ir(bis‐NHC)‐Catalyzed Direct Conversion of Amines to Alcohols in Aqueous Glycerol

Sustainable catalytic conversion of amines to alcohols was realized in the presence of iridium catalysts and aqueous glycerol. Iridium catalysts involving bis‐N‐heterocyclic carbene (bis‐NHC) show good reactivity and stability in the conversion of amines into alcohols in aqueous glycerol. The reaction was initiated with the dehydrogenation of amines and followed by hydrolysis and reduction. Iridium catalysts play dual roles in both the dehydrogenation and reduction steps. By employing glycerol as a solvent and hydrogen source, the final reduction was facilitated. The synthesis and characterization of various Ir(bis‐NHC) complexes are described along with the catalytic reaction results of the amine into alcohol conversion.

Covalent Linkage of an R-ω-Transaminase to a d-Amino Acid Oxidase through Protein Splicing to Enhance Enzymatic Catalysis of Transamination.

R-ω-Transaminases (RTAs) catalyse the conversion of R-configured amines [e.g., (R)-1-phenylethylamine] into the corresponding ketones (e.g., acetophenone), by transferring an amino group from an amino donor [e.g., (R)-1-phenylethylamine] onto an amino acceptor (e.g., pyruvate), resulting in a co-product (e.g., d-alanine). d-Alanine can be deaminated back to pyruvate by d-amino acid oxidase (DAAOs). Here, through in vivo subunit splicing, the N terminus of an RTA subunit (RTAS ) was specifically ligated to the C terminus of a DAAO subunit (DAAOS ) through native peptide bonds (RTA&DAAO). RTAS is in close proximity to DAAOS , at a molecular-scale distance. Thus the transfer of pyruvate and d-alanine between RTA and DAAO can be directional and efficient. Pyruvate→d-alanine→pyruvate cycles are efficiently formed, thus promoting the forward transamination reaction. In a different, in vitro noncovalent approach, based on coiled-coil association, the RTAS N terminus was specifically associated with the DAAOS C terminus (RTA#DAAO). In addition, the two mixed individual enzymes (RTA+DAAO) were also studied. RTA&DAAO has a shorter distance between the paired subunits (RTAS -DAAOS ) than RTA#DAAO, and the number of the paired subunits is higher than in the case of RTA#DAAO, whereas RTA+DAAO cannot form the paired subunits. RTA&DAAO exhibited a transamination catalysis efficiency higher than that of RTA#DAAO and much higher than that of RTA+DAAO.