Addition Of Amines Research Articles

Synthesis of the Marine Alkaloid Cylindricine C and Serendipitous Synthesis of Its 2,13-Di-epi Stereoisomer.

A new approach to the marine alkaloid cylindricine C afforded its previously unreported (±)-2,13-di-epi stereoisomer as the major product along with a minor amount of the racemic parent alkaloid. Key steps included a stereoselective dianion alkylation of a monoester of 1,2-cyclohexanedicarboxylic acid and an annulation based on the tandem conjugate addition of a primary amine to an acetylenic sulfone, followed by intramolecular acylation of the resulting sulfone-stabilized carbanion. The cis-azadecalin moiety thus formed, comprising the cyclohexane A-ring and enaminone B-ring of the products, was further elaborated by the selenenyl chloride-induced cyclofunctionalization of a pendant butenyl substituent with the enaminone moiety, followed by a seleno-Pummerer reaction. Desulfonylation and enaminone reduction afforded the final products. Molecular modeling and X-ray crystallography provided further insight into these processes.

Tissue transglutaminase: a multifunctional and multisite regulator in health and disease.

Tissue transglutaminase (TG2) is a widely distributed multifunctional protein involved in a broad range of cellular and metabolic functions carried out in a variety of cellular compartments. In addition to transamidation, TG2 also functions as a Gα signaling protein, a protein disulfide isomerase (PDI), a protein kinase, and a scaffolding protein. In the nucleus, TG2 modifies histones and transcription factors. The PDI function catalyzes the trimerization and activation of heat shock factor-1 in the nucleus and regulates the oxidation state of several mitochondrial complexes. Cytosolic TG2 modifies proteins by the addition of serotonin or other primary amines and in this way affects cell signaling. Modification of protein-bound glutamines reduces ubiquitin-dependent proteasomal degradation. At the cell membrane, TG2 is associated with G protein-coupled receptors (GPCRs), where it functions in transmembrane signaling. TG2 is also found in the extracellular space, where it functions in protein cross-linking and extracellular matrix stabilization. Of particular importance in transglutaminase research are recent findings concerning the role of TG2 in gene expression, protein homeostasis, cell signaling, autoimmunity, inflammation, and hypoxia. Thus, TG2 performs a multitude of functions in multiple cellular compartments, making it one of the most versatile cellular proteins. Additional evidence links TG2 with multiple human diseases including preeclampsia, hypertension, cardiovascular disease, organ fibrosis, cancer, neurodegenerative diseases, and celiac disease. In conclusion, TG2 provides a multifunctional and multisite response to physiological stress.

Corrosion in Crude Oil Distillation Units (CDUs) and a Study of Reducing Its Rates by Changing Chemical Injection Sites

The injection of chemicals is one of the most important treatment steps used to reduce the effect of corrosion factors in crude oil distillation units in oil refineries. As a result of the availability of suitable conditions for the formation of the main corrosion agents, namely acids (HCI, H2S). It has become necessary to neutralize the effect of these factors in distillation units and towers by changing the sites of adding chemicals, where oil refineries use anti_ corrosion film and caustic soda (NaOH) as well as neutral amine to control and limit the effect of chloride ion, iron rates, salts and the (PH) values. As a result, the research paper is interested in developing a study of adding and changing chemical injection areas (points) of adding chemicals, especially (caustic soda and neutralizer amine) at different specific points, and as it is well known, crude oil passes through a number of different heat exchangers to raise its temperature in preparation for refining. It was found that changing the addition of the neutral amine in the striper tower area of the kerosene section (drops that are returned to the main refinery tower) has a significant effect in controlling the stabilization of pH values between (5.5-6.5) and reducing the iron ion concentration at a rate of (1% ppm), While the injection of caustic soda depends on the temperatures of the crude oil, so it is changed into two lines. The first is before the heat exchangers, that is, when the temperature of the crude oil is (20-35) c̊, and the second line is after the crude oil reaches the temperature (65-90) c̊, it has a significant effect in reducing the concentration of the chloride ion at a rate of (1-5 ppm) present in the form of chloride salts dissolved in the crude oil.

Synthesis of gold(I) diaminocarbene complexes by the addition of amines across coordinated isocyanoferrocene

Gold(I) acyclic diaminocarbene complexes of the [AuCl{C(NHFc)(NR2)}] type (Fc = ferrocenyl) were conveniently synthesized by a one-pot procedure. In this method, 1 equiv. of isocyanoferrocene (FcNC) and an excess of primary or secondary amines R2NH (dimethylamine, morpholine, methylamine, cyclohexylamine, and p-toluidine) are sequentially added to [AuCl(SMe2)] as a gold source in dichloromethane. The stepwise synthesis, in which [AuCl(FcNC)] is the isolated intermediate, worked equally well but generated lower overall yields due to compound loss during the two purification steps. The approach was further extended to synthesize the corresponding cationic biscarbene complexes [Au{C(NHFc)(NR2)}2]Cl simply by using 2 equiv. of FcNC during the “first” reaction step. The compounds form conformational isomers in solution that differ by the orientation of substituents at the carbene units. Based on DFT calculations, these isomers exhibit similar energies (energy difference ≤ 5 kcal mol–1). The crystal structures revealed symmetrical carbene units and the dominant role of the N-H⋅⋅⋅Cl interactions in the crystal assemblies in all cases, which also control the tendency for a particular conformation in the solid state.

Reducing ammonia permeance in poly(acrylonitrile‐co‐butadiene) (NBR)‐based elastomers

AbstractAmmonia (NH3) has emerged as a sustainable future fuel for a low‐carbon future. Ideally, the transportation and storage of ammonia in re‐purposed natural gas networks will dramatically reduce the economic burden associated with converting to ammonia. However, the highly condensable nature and small kinetic diameter of the ammonia means that this fuel readily permeates through the polymer‐based elastomers and gaskets used in natural gas infrastructure. To mitigate this issue, three kinds of additives have been incorporated into the conventional natural gas elastomer poly(acrylonitrile‐co‐butadiene) (NBR) to reduce ammonia permeance. The first is based on increasing the basicity of the elastomer environment, the second provides chemical reactivity with ammonia to limit transport, and the third uses barrier additives to prevent diffusion. The mechanical properties of the modified elastomers; expressed as the tensile stress at yield and Young's modulus were studied. The creation of a basic environment through the addition of amines resulted in moderate changes in ammonia permeability, with up to 50% reduction of ammonia permeability observed from putrescine added NBR. Chemical additives lowered the permeability by up to 20% with limited impact on the tensile properties. The addition of 3% graphene oxide to NBR had the most significant decrease in ammonia permeability, 80%, but also produced a more rigid material. The investigation shows that ammonia permeability can be significantly reduced in NBR elastomers, through the addition of inexpensive additives in tailored strategies.

Hydrogenation of CO2 to MeOH Catalyzed by Highly Robust (PNNP)Ir Complexes Activated by Alkali Bases in Alcohol.

Despite receiving significant attention, well-defined homogeneous complexes for hydrogenation of carbon dioxide (CO2) to methanol (MeOH) are scarce and suffer issues of low catalyst turnover numbers (TONs) at high catalyst concentrations and deactivation in the presence of CO and at elevated temperatures. Herein, we disclose a system deploying sterically demanded (PNNP)Ir complexes for a sustained activity for hydrogenation of CO2 to MeOH at temperatures ∼200 °C in an alcohol solvent. Through reaction optimization, we achieved a TON of ∼9000 for MeOH formation, which exceeds most active homogeneous systems reported to date, and robustness on par with or exceeding most reactive systems utilizing amine additives was demonstrated. The key to achieving sustained catalyst turnover for the system was utilizing a catalytic amount of an alkali base additive, which serves the dual purpose of facilitating more efficient outer-sphere reduction of CO2 and HCO2Et and enhancing the selectivity of MeOH over in situ formed CO.

Publisher's Note

Publisher's Note

Group IV Complexes with Sterically Congested N-Aryl-adamantylcarbamidate Ligands.

Metalation of N-(2,6-dibenzhydryl-4-tolyl)adamantane-1-carboxamide (1, Ar*N(H)-C(O)-Ad) with M(NMe2)4 (M = Ti, Zr, Hf) yields amidate complexes Ar*N=C(Ad)-O-Ti(NMe2)3 (2) as well as bis(amidate) compounds (Ar*N=C(Ad)-O)2M(NMe2)2 (M = Zr (3), Hf (4)). In 2, the amidate ligand acts as a monodentate base via the oxygen atom with the Ti center in a slightly distorted tetrahedral environment. The steric requirement of the amidate ligand stabilizes the small coordination number of four of the Ti atom. In congeners 3 and 4, two bidentate amidate ligands exist in the coordination spheres, leading to hexacoordinate group IV metal atoms. The small bite angles of the Zr- and Hf-bound amidate ligands lead to severe distortion of the octahedral environments of the Zr and Hf centers. Titanium compound 2 is an unsuitable choice to catalyze hydrofunctionalization of alkynes with amines and phosphane oxides and despite the significantly smaller pKa value of the carboxylic amide, formation of carboxamide 1 is the dominant reaction upon addition of amines or phosphane oxides to release intramolecular steric strain introduced by the very bulky adamantylamidato ligand.

Synthesis of Composites for the Removal of F- Anions.

This work presents the synthesis of amine and ferrihydrite functionalized graphene oxide for the removal of fluoride from water. The synthesis of the graphene oxide and the modified with amine groups is developed by following the modified Hummer's method. Fourier transform infrared spectrometry, X-ray, Raman spectroscopy, thermogravimetric analysis, surface charge distribution, specific surface area and porosity, adsorption isotherms, and the van't Hoff equation are used for the characterization of the synthesized materials. Results show that the addition of amines with ferrihydrite generates wrinkles on the surface layers, suggesting a successful incorporation of nitrogen onto the graphene oxide; and as a consequence, the adsorption capacity per unit area of the materials is increased.

Theoretical Insight into the Mechanism of Cu(I)-Catalyzed [2 + 2 + 1] Cycloaddition to β-Pyrrolinones: Azaheterocycle Formation and Assisted Dehydrogenation with Solvent MeNO2.

The construction of multisubstituted β-pyrrolinones from simple starting materials remains a great challenge. Recently, a novel Cu(I)-catalyzed [2 + 2 + 1] cycloaddition reaction was developed for rapid access to fully substituted β-pyrrolinones, which are difficult to synthesize through traditional methods as this approach may involve unusual C-nucleophilic addition of enamines and umpolung of imines. Elucidating the reaction mechanism may inspire the development of new methodologies via the unusual C-nucleophilic addition of enamines and imines. However, the reaction mechanism is still unclear because none of the intermediates was observed during the reaction process. In this work, we employed theoretical and computational chemistry to investigate the possible pathway. Finally, the calculated results indicate that ketene formed by the Wolff rearrangement of α-diazo-β-ketoester reacts with enamine formed by the addition of alkynes and amine, affording the five-membered azaheterocycle, and this process involves the formation of a six-membered ring intermediate and sequential isomerization, and the further dehydrogenation needs to be assisted with solvent MeNO2.

Synthesis of 3, 5-Disubstituted-Tetrahydro-2h-1, 3, 5-Thiadiazine2-Thiones Derivatives and their Metal Complexes as Potential Bioactive Agents

Thiadiazine thione derivatives (2-(5-(2-.hydroxyethyl)-2-thioxo-1,3,5-thiadiazinane-3-yl) Acetic acid, 2-(5-.butyl-6-thioxo.-1, 3, 5-thiadiazinane-3-yl) Acetic acid, 2, 1 and 2 were synthesized by the reaction of alkyl primary amines (glycine, butylamine) with carbon disulfide and potassium hydroxide followed by addition of formaldehyde and various primary amines (ethanolamine, glycine) in phosphate buffer medium. The synthesized compounds were transformed into organometallic complexes (3-12) Ni (II), Co (II), Cu (II), Zn (II) and Fe (II) using their metal salts. The structure determinations of these compounds were elucidated by spectral methods such as IR, NMR spectroscopy and Mass spectrometry. All the synthesized compounds were screened for their anti-microbia++l activities. Their structure activity relationship showed that the potential of tested compounds enhanced with metal complexes against evaluated activities.

Electrostatic Interactions in Asymmetric Organocatalysis.

ConspectusElectrostatic interactions are ubiquitous in catalytic systems and can be decisive in determining the reactivity and stereoselectivity. However, difficulties quantifying the role of electrostatic interactions in transition state (TS) structures have long stymied our ability to fully harness the power of these interactions. Fortunately, advances in affordable computing power, together with new quantum chemistry methods, have increasingly enabled a detailed atomic-level view. Empowered by this more nuanced perspective, synthetic practitioners are now adopting these techniques with growing enthusiasm.In this Account, we narrate our recent results rooted in state-of-the-art quantum chemical computations, describing pivotal roles for electrostatic interactions in the organization of TS structures to direct the reactivity and selectivity in the realm of asymmetric organocatalysis. To provide readers with a fundamental foundation in electrostatics, we first introduce a few guiding principles, beginning with a brief discussion of how electrostatic interactions can be harnessed to tune the strength of noncovalent interactions. We then describe computational approaches to capture these effects followed by examples in which electrostatic effects impact structure and reactivity. We then cover some of our recent computational investigations in three specific branches of asymmetric organocatalysis, beginning with chiral phosphoric acid (CPA) catalysis. We disclose how CPA-catalyzed asymmetric ring openings of meso-epoxides are driven by stabilization of a transient partial positive charge in the SN2-like TS by the chiral electrostatic environment of the catalyst. We also report on substrate-dependent electrostatic effects from our study of CPA-catalyzed intramolecular oxetane desymmetrizations. For nonchelating oxetane substrates, electrostatic interactions with the catalyst confer stereoselectivity, whereas oxetanes with chelating groups adopt a different binding mode that leads to electrostatic effects that erode selectivity. In another example, computations revealed a pivotal role of CH···O and NH···O hydrogen bonding in the CPA-catalyzed asymmetric synthesis of 2,3-dihydroquinazolinones. These interactions control selectivity during the enantiodetermining intramolecular amine addition step, and their strength is modulated by electrostatic effects, allowing us to rationalize the effect of introducing o-substituents. Next, we describe our efforts to understand selectivity in a series of NHC-catalyzed kinetic resolutions, where we discovered that the electrostatic stabilization of key proton(s) is the common driver of selectivity. Finally, we discuss our breakthrough in understanding asymmetric silylium ion-catalyzed Diels-Alder cycloaddition of cinnamate esters to cyclopentadienes. The endo:exo of these transformations is guided by electrostatic interactions that selectively stabilize the endo-transition state.We conclude with a brief overview of the outstanding challenges and potential roles of computational chemistry in enabling the exploitation of electrostatic interactions in asymmetric organocatalysis.

Anti-Markovnikov Intermolecular Hydroamination of Alkenes and Alkynes: A Mechanistic View.

Hydroamination, the addition of an N-H bond across a C-C multiple bond, is a reaction with a great synthetic potential. Important advances have been made in the last decades concerning catalysis of these reactions. However, controlling the regioselectivity in the amine addition toward the formation of anti-Markovnikov products (addition to the less substituted carbon) still remains a challenge, particularly in intermolecular hydroaminations of alkenes and alkynes. The goal of this review is to collect the systems in which intermolecular hydroamination of terminal alkynes and alkenes with anti-Markovnikov regioselectivity has been achieved. The focus will be placed on the mechanistic aspects of such reactions, to discern the step at which regioselectivity is decided and to unravel the factors that favor the anti-Markovnikov regioselectivity. In addition to the processes entailing direct addition of the amine to the C-C multiple bond, alternative pathways, involving several reactions to accomplish anti-Markovnikov regioselectivity (formal hydroamination processes), will also be discussed in this review. The catalysts gathered embrace most of the metal groups of the Periodic Table. Finally, a section discussing radical-mediated and metal-free approaches, as well as heterogeneous catalyzed processes, is also included.

Study on CO2 adsorption performance of biocarbon synthesized in situ from nitrogen-rich biomass pomelo peel

Recycling biomass to prepare CO2 adsorbent has been emphasized due to the benefits such as easy availability of materials, green and sustainable. Furthermore, functional groups containing nitrogen can promote the capacity of biochar to adsorb CO2. Usually, the production of N-doped porous carbon involves the chemical addition of amines or compounds containing nitrogen, which leads to pore blockage. For this reason, pomelo peel was used as a nitrogen-rich precursor of biomass to achieve nitrogen self-doping in this paper, and ZnCl2 was uniformly loaded as an activator using the impregnation method. After carbonization at 800 ℃ and template removal, an efficient porous carbon adsorbent was obtained without adding extra nitrogen sources. The N content of the biocarbon was retained from 2.60 to 5.98 at% employing pre-carbonation. We also systematically analyzed the modification of the CO2 adsorption effect by ultra-microporous structure and N atom doping. The former content showed almost no linear correlation with the adsorption data, but rather a synergistic effect with N content influenced the adsorption results under environmental conditions. The optimal adsorption of CO2 was 3.01 mmol g−1 (25 °C, 1 bar) and 4.83 mmol g−1 (0 °C, 1 bar). In addition, the adsorbent PPC-4 has excellent CO2/N2 adsorption selectivity of 38 and cyclic adsorption performance.

Determination of enantiodiscrimination of chiral acids and tetrahydropyrimidine derivatives by bis-thiourea derived chiral solvating agents by NMR spectroscopy

Synthesis of four derivatives of chiral bis-thiourea have been prepared from (S)-(1- isocyanatoethyl)benzene and diamines. The bis-thiourea derivatives were scanned as Chiral Solvating Agents (CSA) for detecting discrimination of optically pure acids by 1H NMR spectroscopy. Addition of amine during NMR experiments was found essential to effect deprotonation of carboxylic acid substrates. The present CSA were found to show effective chiral discrimination of neutral analytes such as tetrahydropyrimidine derivatives. Further they showed good molecular recognition in case of 1,4-dihydropyridine carboxylic acid, an intermediate of cardiovascular drug Benidipine-HCl and ibuprofen.

Synthesis of Highly Substituted 3-Acylpyrroles by a Four-Component Sonogashira Alkynylation–Amine Addition–Nitroalkene Michael Addition–Cyclocondensation

AbstractA consecutive four-component alkynylation–amine addition–nitroalkene addition–cyclocondensation one-pot reaction of acid chlorides, alkynes, amines, and nitroalkenes furnished a library of 3-acylpyrroles in modest to good yields. The sequence takes advantage of a synergism between a Brønsted acid (acetic acid) and a Lewis acid [iron(III) chloride] in the terminal addition-cyclocondensation step of the intermediately formed enaminones with nitroalkenes.

Effect of addition of polyether amine and TiO2 nanofibers on the properties of PEO based sodium ion conducting composites

Sodium ion conducting polymer composite films have been prepared using the blend of poly (ethylene oxide) and polyetheramine (JEFFAMINE ED2003) in which sodium trifluoromethane sulfonate (NaTf) salt and varying amounts of inorganic filler (TiO2 nanofibers) have been added. The effect of TiO2 nanofibers addition has been seen in terms of improved ionic conductivity and electrochemical stability of the nanocomposite film. Highest ionic conductivity of ∼3.5 × 10⁻⁵ Scm⁻1 (at room temperature) along with an electrochemical stability up to ∼2.6 V has been obtained for PEO-Jeffamine blend based solid polymer electrolyte (SPE) with 10 wt% of NaTf salt and a small amount (0.2 wt%) of TiO2 nanofibers. A non monotonic variation in the room temperature ionic conductivity and intensity of XRD peaks has been seen for composite films with increasing concentration of TiO2 nanofibers. Uniform distribution of salt (Na, F and S) and TiO2 nanofibers in the prepared composite film has been obtained in the elemental mapping. FTIR results have given evidence of interaction between the blended polymers, salt and TiO2. The wavelength and duration of exposure of UV radiation have altered the electrical properties of film. Increase in the number of ionic charge carriers has been attained on exposure to UV radiation.

On the Stereochemistry of the NH Bond Activation of Ammonia or Amines by Disilenes: Predictability.

The stereochemistry of the addition of NH3 to the stereoisomers of 1,2-di-tert-butyl-1,2-bis(2,4,6-triisopropylphenyl)disilene (Z-5 or E-5) is 100 % stereospecific giving two isomeric disilylamines 6 and 7, respectively, derived from syn-addition to the stereoisomeric disilenes. Variable Time Normalization Analysis studies of the reaction of tetramesityldisilene (3) with isopropylamine (iPrNH2) revealed that the order in both amine and disilene is 1. The kinetic isotope effect for the addition of iPrNH2/iPrND2 to tetramesityldisilene was determined to be 3.04 ± 0.06 at 298 K, a primary KIE, indicating that the proton is transferred in the rate determining step. Competition studies between the addition of PrNH2 and iPrNH2 to tetramesityldisilene resulted in the exclusive formation of the PrNH2 adduct consistent with a nucleophilic addition. Computational studies of the mechanism of the addition of ammonia to E-5 revealed the lowest energy pathway involves the formation of the donor adduct derived from syn-addition, followed by intramolecular syn-transfer of the proton. The results of this studyallow for a refinement of our understanding of the mechanism of this important fundamental reaction in disilene chemistry, and allow us to understand our ability to reliably predict the stereochemical outcomes of future NH σ-bond activation reactions.

Temporally Stable Supramolecular Polymeric Salts Enabling High-Performance 3D All-Aromatic Polyimide Lattices.

Vat photopolymerization (VP) Additive Manufacturing (AM), in which UV light is selectively applied to cure photo-active polymers into complex geometries with micron-scale resolution, has a limited selection of aliphatic thermoset materials that exhibit relatively poor thermal performance. Ring-opening dianhydrides with acrylate-containing nucleophiles yielded diacrylate ester-dicarboxylic acids that enabled photo-active polyimide (PI) precursors, termed polysalts, upon neutralization with an aromatic diamine in solution. In situ FTIR spectroscopy coupled with a solution and photo-rheological measurements revealed a previously unknown time-dependent instability of 4,4'-oxydianiline (ODA) polysalts due to an aza-Michael addition. Replacement of the electron-donating ether-containing diamine with an electron withdrawing sulfone-containing monomer, e.g., 4,4'-diaminodiphenyl sulfone (DDS), prohibited the aza-Michael addition of the aromatic amine to the activated acrylate double bond. Novel DDS polysalt photocurable solutions are similarly analyzed and validated long-term stability, which enabled reproducible printing of polyimide organogel intermediates. Subsequent VP AM afforded 3-dimensional (3D) structures of intricate complexity and excellent surface finish, as demonstrated with scanning electron microscopy. In addition, the novel PMDA-HEA/DDS solution enabled the production of the first beam latticed architecture comprised of all-aromatic polyimide. The versatility of a polysalt platform for multi-material printing is further demonstrated by printing parts with alternating polysalt compositions.

Intermolecular Dearomative 1,2-Amination/Carbonylation via Nucleophilic Addition of Simple Amines to Arene π-Bonds.

The incorporation of the privileged amino functionality is of paramount importance in organic synthesis. In contrast to the well-developed amination methods for alkenes, the dearomative amination of arenes is largely underexplored due to the inherently inert reactivity of arene π-bonds and selectivity challenges. Herein, we report an intermolecular dearomative aminofunctionalization via direct nucleophilic addition of simple amines to chromium-bound arenes. This multicomponent 1,2-amination/carbonylation reaction enables rapid access to complicated alicyclic compounds containing amino and amide functionalities from benzene derivatives under CO-gas-free conditions, which also represents the first application of nitrogen-based nucleophiles in η6-coordination-induced arene dearomatizations.