Reaction Of Oximes Research Articles

Study of adsorption performance and adsorption mechanism for U(VI) ion on modified polyacrylonitrile fibers

The modified polyacrylonitrile fibers (ACPAN fibers) was synthesized by oximation reaction and alkaline hydrolysis. ACPAN fibers was characterized by means of SEM, FTIR, XPS and elementary analysis. The effects of contact time, solid–liquid ratio, pH, ionic strength, initial concentration and temperature on U(VI) adsorption onto ACPAN fibers was studied and the adsorption mechanism was also discussed. The experimental data fitted well pseudo-second-order kinetics model and Freundlich and D–R models, and thermodynamic process was an endothermic and spontaneous reaction. The maximum adsorption capacity was 163 mg/g, and U(VI) and ACPAN fibers possible formed more stable penta-coordination complexation. This paper highlighted ACPAN fibers as a good adsorbent to remove efficiently and economically uranyl from radioactive wastewater.

Mechanochemical Synthesis and Isomerization of N-Substituted Indole-3-carboxaldehyde Oximes †.

Performing solution-phase oximation reactions with hydroxylamine hydrochloride (NH2OH·HCl) carries significant risk, especially in aqueous solutions. In the present study, four N-substituted indole-3-carboxaldehyde oximes were prepared from the corresponding aldehydes by solvent-free reaction with NH2OH·HCl and a base (NaOH or Na2CO3) using a mechanochemical approach, thus minimizing the possible risk. In all cases, the conversion to oximes was almost complete. The focus of this work is on 1-methoxyindole-3-carboxaldehyde oxime, a key intermediate in the production of indole phytoalexins with useful antimicrobial properties. Under optimized conditions, it was possible to reach almost 95% yield after 20 min of milling. Moreover, for the products containing electron-donating substituents (-CH3, -OCH3), the isomerization from the oxime anti to syn isomer under acidic conditions was discovered. For the 1-methoxy analog, the acidic isomerization of pure isomers in solution resulted in the formation of anti isomer, whereas the prevalence of syn isomer was observed in solid state. From NMR data the syn and anti structures of produced oximes were elucidated. This work shows an interesting and possibly scalable alternative to classical synthesis and underlines environmentally friendly and sustainable character of mechanochemistry.

New MnIIMnIII8 and MnII2MnIII10MnIV2 clusters from the reaction of methyl 2-pyridyl ketone oxime with [Mn12O12(O2CR)16(H2O)4

The syntheses, crystal structures and magnetic properties of two mixed-valence Mn clusters [MnIIMnIII8O6(mpko)3(O2CMe)11] (1) and [MnII2MnIII10MnIV2O12(mpko)6(O2CPh)12(H2O)2] (2) are reported. They were obtained from the corresponding reactions in MeCN of [Mn12O12(O2CR)16(H2O)4] (R = Me (3), Ph (4)) with eight equivalents of methyl(pyridine-2-yl)ketone oxime (mpkoH). The cores of 1 and 2 are structurally related: 1 possesses a [Mn9(µ3-O)6]14+ core with an unusual topology comprising a near-planar MnIII-centered MnIII6 hexagon with additional MnII and MnIII ions above and below the plane. Complex 2 possesses a [Mn14(µ4-O)2(µ3-O)10]18+ core that can be described as a dimer of two Mn7 incomplete-cores of 1. It is also a rare example of a Mn cluster containing three Mn oxidation states. Fits of variable-temperature, solid-state dc magnetic susceptibility data collected in a 0.1 T field in the 5.0–300 K range established that 1 and 2 possess ground state spins of S = 3/2 and S = 1, respectively, which were confirmed by ac in-phase susceptibility data.

Benzaldoxime to benzamide rearrangement catalysed by rhodium(III) hydroxocomplexes: The influence of polynuclear species

Rhodium(III) hydroxide was shown previously to possess the catalytic activity in the rearrangement reaction of primary oximes to amides. Alkaline solutions of rhodium(III) chlorocomplexes are routinely used for Rh(OH)3 preparation and allow for a diversity of rhodium hydroxocomplexes that hold a wide range of catalytic properties. In this study, two Al2O3 supported catalysts containing 1) exclusively [Rh(OH)6]3− species and 2) a mixture of rhodium hydroxocomplexes with one to four rhodium atoms ([Rh(OH)6]3–, [Rh2(μ−OH)2(OH)8]4–, [Rh3(μ−OH)3(OH)12]6–, [Rh4(μ−OH)6(OH)12]6) were prepared, characterised (XRD, Raman, EXAFS) and tested in the benzaldoxime to benzamide rearrangement. The catalyst containing polynuclear complexes possessed at least three times higher turnover frequency (TOF) and better selectivity than the [Rh(OH)6]3– based catalyst. According to the EXAFS data, the reduction of rhodium(III) took place under reaction conditions yielding small rhodium clusters (CNRh-Rh = 4), which were proposed to be the active sites of catalysts.

Origin of Regiochemical Control in Rh(III)/Rh(V)-Catalyzed Reactions of Unsaturated Oximes and Alkenes to Form Pyrdines

The Rh(III)-catalyzed reactions of α,β-unsaturated oximes with alkenes are versatile methods for the synthesis of pyridines. Density functional theory (DFT) calculations reported here reveal the de...

Photoredox-Catalyzed Sulfonylation of O-Acyl Oximes via Iminyl Radicals with the Insertion of Sulfur Dioxide.

A multicomponent sulfonylation of O-acyl oximes via iminyl radicals with the insertion of sulfur dioxide under photoredox catalysis is achieved. This multicomponent reaction of O-acyl oximes, potassium metabisulfite, alkenes, and nucleophiles under visible-light irradiation is efficient, giving rise to a range of sulfones in moderate to good yields. A broad reaction scope is presented with good functional group compatibility.

Tunable Aminooxy-Functionalized Monolayer-Protected Gold Clusters for Non-Polar or Aqueous Oximation Reactions.

Aminooxy (-ONH2) groups are well known for their chemoselective reactions with carbonyl compounds, specifically aldehydes and ketones. The versatility of aminooxy chemistry has proven to be an attractive feature that continues to stimulate new applications. This work describes application of aminooxy 'click chemistry' on the surface of gold nanoparticles. We present here a trifunctional amine-containing aminooxy alkane thiol ligand for use in the functionalization of gold monolayer protected clusters (Au MPCs). Diethanolamine is readily transformed into an organic-soluble aminooxy thiol (AOT) ligand using a short synthetic path. The synthesized AOT ligand was coated on ≤ 2 nm diameter hexanethiolate (C6S)-capped Au MPCs using a ligand exchange protocol to afford organic-soluble AOT/C6S (1:1 ratio) Au mixed monolayer protected clusters (MMPCs). This work describes the synthesis of Au(C6S)(AOT) MMPCs and representative oximation reactions with various types of aldehyde-containing molecules, highlighting the ease and versatility of the chemistry and how amine protonation can be used to switch solubility characteristics.

Polypropylene nonwoven fabric modified with oxime and guanidine for antibiofouling and highly selective uranium recovery from seawater

A novel adsorbent for antibiofouling and highly selective uranium recovery from seawater is developed in this work. Specifically, the polypropylene nonwoven fabric modified with oxime and guanidine was obtained by subsequent radiation-grafting, ring-opening and oximation reaction. The adsorbent demonstrates outstanding selectivity for uranium(VI) against other competing metal ions in real seawater. The antibacterial assay indicated the adsorbent has good antibacterial properties against Escherichia coli and Staphylococcus aureus. XPS spectra indicate that uranium(VI) is adsorbed on the non-woven through the interaction with multiple groups. This work shows that the sorbent may be a hopeful material for the extraction of uranium from seawater.

Cu(OAc)2-Triggered Cascade Reaction of Malonate-Tethered Acyl Oximes with Indoles, Indole-2-alcohols, and Indole-2-carboxamides.

A Cu(OAc)2-promoted cascade reaction of malonate-tetherd acyl oximes with indoles, indole-2-alcohols, or indole-2-carboxmides provides facile access to polysubstituted 3-pyrrolin-2-ones. The reaction features the generation of two adjacent electrophilic centers at the same time as cyclization to lactam. The subsequent double addition with nucleophiles followed by oxidation realizes the difunctionalization of the imine sp2-carbon and the adjacent α-sp3-carbon.

Cover Feature: The Influence of β‐Ammonium Substitution on the Reaction Kinetics of Aminooxy Condensations with Aldehydes and Ketones (ChemPhysChem 6/2019)

The Cover Feature illustrates the key transition structure facilitating the oximation reaction of 2-(aminooxy)-N, N-dimethylethan-1-ammonium chloride (ADMH) with acetone. The click-chemistry capture of volatile aldehydes and ketones by ammonium aminooxy compounds is an efficient means of analyzing the carbonyl subset in complex mixtures. The image represents the use of oximation reactions in devices where vapor, represented by the droplet, is fed from the source, represented by the light in the bottom-right-hand corner. More information can be found in the Article by M. A. Ogunwale et al. on page 815 in Issue 6, 2019 (DOI: 10.1002/cphc.201801143).

The Influence of β-Ammonium Substitution on the Reaction Kinetics of Aminooxy Condensations with Aldehydes and Ketones.

The click-chemistry capture of volatile aldehydes and ketones by ammonium aminooxy compounds has proven to be an efficient means of analyzing the carbonyl subset in complex mixtures, such as exhaled breath or environmental air. In this work, we examine the carbonyl condensation reaction kinetics of three aminooxy compounds with varying β-ammonium ion substitution using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). We determined the activation energies for the reactions of the aminooxy compounds ATM, ADMH and AMAH with a panel of ketones and aldehydes that included acrolein and crotonaldehyde. The measurements indicate that the activation energies for the oximation reactions are quite low, less than 75 kJ mol-1 . ADMH is observed to react the fastest with the carbonyls studied. We postulate this result may be attributed to the ADMH ammonium proton effecting a Brønsted-Lowry acid-catalyzed elimination of water during the rate-determining step of oxime ether formation. A theoretical study of oxime ether formation is presented to explain the enhanced reactivity of ADMH relative to the tetraalkylammonium analog ATM.

Scale-up of microdroplet reactions by heated ultrasonic nebulization.

Dramatically higher rates for a variety of chemical reactions have been reported in microdroplets compared with those in the liquid bulk phase. However, the scale-up of microdroplet chemical synthesis has remained a major challenge to the practical application of microdroplet chemistry. Heated ultrasonic nebulization (HUN) was found as a new way for scaling up chemical synthesis in microdroplets. Four reactions were examined, a base-catalyzed Claisen-Schmidt condensation, an oximation reaction from a ketone, a two-phase oxidation reaction without the use of a phase-transfer-catalyst, and an Eschenmoser coupling reaction. These reactions show acceleration of one to three orders of magnitude (122, 23, 6536, and 62) in HUN microdroplets compared to the same reactions in bulk solution. Then, using the present method, the scale-up of the reactions was achieved at an isolated rate of 19 mg min-1 for the product of the Claisen-Schmidt condensation, 21 mg min-1 for the synthesis of benzophenone oxime from benzophenone, 31 mg min-1 for the synthesis of 4-methoxybenzaldehyde from 4-methoxybenzyl alcohol, and 40 mg min-1 for the enaminone product of the Eschenmoser coupling reaction.

A Density Functional Theory Study of 3,5-dichlorosalicyliden-p-iminoacetophenone oxime Complexes with Co, Ni, Cu and Zn Metals

In this work, new Schiff baz ligand was synthesized by reaction of p-iminoacetophenone oxime with 3,5-dichlorosalicylaldehyde. Metal complexes of Co+2, Ni+2, Cu+2 and Zn+2 acetate metal salts were synthesized with this ligand. The ligand and complexes are characterized in experimental by their elemental analyses, X-ray, 1H-NMR, 13C-NMR, UV-Vis, FT-IR, magnetic susceptibility and thermogravimetric analyses (TGA) and also have been investigated by using quantum mechanical methods. The transition metals are coordinated to the schiff base through the azomethine nitrogen and the carboxyl oxygen atom. Obtained metal complexes were studied the magnetic properties and their geometries were determined. Co+2, Ni+2 and Zn+2 complexes have been found tetrahedral geometry and Cu+2 complex has been found four coordinated geometry.

Au-catalyzed skeletal rearrangement of O-propargylic oximes via N-O bond cleavage with the aid of a Brønsted base cocatalyst.

O-Propargylic oximes that possess an electron-withdrawing aryl group on the oxime moiety undergo Au-catalyzed skeletal rearrangements via N-O bond cleavage to afford the corresponding 2H-1,3-oxazine derivatives. Our studies show that the inclusion of a Brønsted base cocatalyst not only accelerates the reaction but also switches pathways of the skeletal rearrangement reaction, realizing divergent synthesis of heterocyclic compounds. Computational studies indicate that the elimination of propargylic proton in the cyclized vinylgold intermediate is rate-determining and both electron-withdrawing substituents at the oxime moiety and base cocatalyst facilitate the proton elimination. Moreover, the protodeauration process proceeds stepwise involving N-O bond cleavage followed by recyclization to construct the oxazine core.

Influence of ions to modulate hydrazone and oxime reaction kinetics to obtain dynamically cross-linked hyaluronic acid hydrogels

Simple monovalent and divalent salts are presented as a novel catalyst for performing hydrazone and oxime coupling chemistry at physiological pH with excellent yields.

Gold-Catalyzed Cyclization/Intermolecular Methylene Transfer ­Sequence of O-Propargylic Oximes Derived from Glyoxylates

We successfully extended our gold-catalyzed skeletal rearrangement reaction of O-propargylic oximes through C=N bond cleavage to include substrates having an ester group on the oxime moiety, affording the corresponding 2-isoxazolines having an alkoxycarbonylmethylene group at the 4-position in good to high yields. Our mechanistic studies indicated that the transfer of the alkoxycarbonylmethylene group proceeded in an intermolecular manner, confirming that the reaction proceeds through cyclization followed by intermolecular transfer of the alkoxycarbonylmethylene group.

Gallic Acid-Promoted SET Process for Cyclobutanone Oximes Activation and (Carbonylative-)Alkylation of Olefins

Despite the general success of metal catalysts in modern organic chemistry, the exploration of natural available organic molecules as catalysts still has a strong appeal to scientists because of their green and sustainable advantages. Herein an intermolecular coupling reaction of cyclobutanone oximes with olefins promoted by biowaste gallic acid is reported. Both alkylation and carbonylative alkylation reactions proceeded well in this system. Various cyclobutanone oximes and olefins can be transformed into the corresponding products in moderate to good yields. Detailed EPR investigations and control experiments are consistent with a single-electron transfer mechanism.

Improvement of Liquid Crystal Alignment Using Novel Photo-Activators.

Photo-activator is a kind of additive that can improve the anchoring energy by attacking some of the bonds of polyimide (PI). Photo-activators were synthesized from the reaction of cyclohexanone oxime with three different anhydrides, respectively. Each activator generates different active radicals when irradiated. These fragmented and activated radicals are responsible for the liquid crystal (LC) alignment of PI film. The reactivity was confirmed through UV-Visible spectroscopy. All the three photo-activators had characteristic bimodal-shaped absorption peaks at 270∼280 nm. The photofragmentation reactions were completed within 1 min of UV irradiation, which implies that the activators are highly reactive to UV light. The short reaction time is very useful for liquid crystal display (LCD) factory applications. The photo-activator using crotonic anhydride (CAP) showed the highest surface anchoring energy, of 6.92 × 10-5 J/m2, compared to that of the other activators and that obtained by rubbing methods; (1.11 × 10-5 J/m2). This result was obtained due to resonance stabilization from the allyl radicals of CAP. The photo-activator using acetic anhydride (AAP) reached its maximum anchoring energy in less than 3 min of irradiation, which is the shortest optimum irradiation time. Considering the fact that this process does not require additional procedure and time, the photo-activators can be considered an innovate additive.

Copper-catalyzed radical oxytrifluoromethylation of alkenyl oximes at ambient temperature

A mild and efficient copper-catalyzed radical oxytrifluoromethylation reaction of alkenyl oximes was successfully developed. The method provides a straightforward access to a wide range of CF3-containing isoxazolines in good to excellent yields.

Click Chemistry-Based Injectable Hydrogels and Bioprinting Inks for Tissue Engineering Applications.

The tissue engineering and regenerative medicine approach require biomaterials which are biocompatible, easily reproducible in less time, biodegradable and should be able to generate complex three-dimensional (3D) structures to mimic the native tissue structures. Click chemistry offers the much-needed multifunctional hydrogel materials which are interesting biomaterials for the tissue engineering and bioprinting inks applications owing to their excellent ability to form hydrogels with printability instantly and to retain the live cells in their 3D network without losing the mechanical integrity even under swollen state. In this review, we present the recent developments of in situ hydrogel in the field of click chemistry reported for the tissue engineering and 3D bioinks applications, by mainly covering the diverse types of click chemistry methods such as Diels-Alder reaction, strain-promoted azide-alkyne cycloaddition reactions, thiol-ene reactions, oxime reactions and other interrelated reactions, excluding enzyme-based reactions. The click chemistry-based hydrogels are formed spontaneously on mixing of reactive compounds and can encapsulate live cells with high viability for a long time. The recent works reported by combining the advantages of click chemistry and 3D bioprinting technology have shown to produce 3D tissue constructs with high resolution using biocompatible hydrogels as bioinks and in situ injectable forms. Interestingly, the emergence of click chemistry reactions in bioink synthesis for 3D bioprinting have shown the massive potential of these reaction methods in creating 3D tissue constructs. However, the limitations and challenges involved in the click chemistry reactions should be analyzed and bettered to be applied to tissue engineering and 3D bioinks. The future scope of these materials is promising, including their applications in in situ 3D bioprinting for tissue or organ regeneration.