Synthesis Of Oximes Research Articles

In situ Generation of Cyclohexanone Drives Electrocatalytic Upgrading of Phenol to Nylon‐6 Precursor

AbstractCoupling in situ generated intermediates with other substrates/intermediates is a viable approach for diversifying product outcomes of catalytic reactions involving two or multiple reactants. Cyclohexanone oxime is a key precursor for caprolactam synthesis (the monomer of Nylon‐6), yet its current production uses unsustainable carbon sources, noble metal catalysts, and harsh conditions. Herein, we report the first work to synthesize cyclohexanone oxime through electroreduction of phenol and hydroxylamine. The Faradaic efficiency reached 69.1 % over Cu catalyst, accompanied by a corresponding cyclohexanone oxime formation rate of 82.0 g h−1 gcat−1. In addition, the conversion of phenol was up to 97.5 %. In situ characterizations, control experiments, and theoretical calculations suggested the importance of balanced activation of water, phenol, and hydroxylamine substrates on the optimal metallic Cu catalyst for achieving high‐performance cyclohexanone oxime synthesis. Besides, a tandem catalytic route for the upgrading of lignin to caprolactam has been successfully developed through the integration of thermal catalysis, electrocatalysis, and Beckmann rearrangement, which achieved the synthesis of 0.40 g of caprolactam from 4.0 g of lignin raw material.

Synthesis of Oximes by Nickel-Catalyzed Coupling of Nitrates with Organohalides

Synthesis of Oximes by Nickel-Catalyzed Coupling of Nitrates with Organohalides

In situ Generation of Cyclohexanone Drives Electrocatalytic Upgrading of Phenol to Nylon-6 Precursor.

Coupling in situ generated intermediates with other substrates/intermediates is a viable approach for diversifying product outcomes of catalytic reactions involving two or multiple reactants. Cyclohexanone oxime is a key precursor for caprolactam synthesis (the monomer of Nylon-6), yet its current production uses unsustainable carbon sources, noble metal catalysts, and harsh conditions. Herein, we report the first work to synthesize cyclohexanone oxime through electroreduction of phenol and hydroxylamine. The Faradaic efficiency reached 69.1 % over Cu catalyst, accompanied by a corresponding cyclohexanone oxime formation rate of 82.0 g h-1 gcat -1. In addition, the conversion of phenol was up to 97.5 %. In situ characterizations, control experiments, and theoretical calculations suggested the importance of balanced activation of water, phenol, and hydroxylamine substrates on the optimal metallic Cu catalyst for achieving high-performance cyclohexanone oxime synthesis. Besides, a tandem catalytic route for the upgrading of lignin to caprolactam has been successfully developed through the integration of thermal catalysis, electrocatalysis, and Beckmann rearrangement, which achieved the synthesis of 0.40 g of caprolactam from 4.0 g of lignin raw material.

Electrocatalytic ORR-coupled ammoximation for efficient oxime synthesis.

State-of-the-art technology for cyclohexanone oxime production typically demands elevated temperature and pressure, along with the utilization of expensive hydroxylamine sulfate or oxidants. Here, we propose an electrochemistry-assisted cascade strategy for the efficient cyclohexanone ammoximation under ambient conditions by using in situ cathode-generated green oxidants of reactive oxygen species (ROS) such as OOH* and H2O2. This electrochemical reaction can take place at the cathode, achieving over 95% yield, 99% selectivity of cyclohexanone oxime, and an electron-to-oxime (ETO) efficiency of 96%. Mechanistic analysis reveals that, in addition to the direct ammoximation by in situ-generated OOH* by electrocatalytic ORR, Ti-MOR also play a major role in capturing OOH* directly and converting the in situ-generated H2O2 to OOH*, thus accelerating the ORR-coupled cascade production of cyclohexanone oxime. This work paves a mild, economical, and sustainable energy-efficient electrocatalytic route for the oxime production using oxygen, ammonium bicarbonate, and cyclohexanone.

Thymoquinone oxime synthesis and its effects on melanoma cells: cytotoxic, genotoxic, and apoptotic evaluation

Strong evidence supports the anticancer properties of natural plant product isolates. The cytotoxic, genotoxic, and apoptotic properties of an oxime derivative of thymoquinone (TQ) in melanoma cancer cells were investigated. The structure of TQ-Oxime was elucidated through nuclear magnetic resonance, and its effect on B16F10 and L929 cell lines was assessed using a luminometric adenosine triphosphate assay. Intracellular reactive oxygen species (iROS) were quantified via fluorometry, mitochondrial membrane potential (MMP) was assessed using flow cytometry, glutathione (GSH) levels were measured using a luminometric GSH/oxidized glutathione assay, DNA damage via comet assay, and apoptosis was detected using acridine orange/ethidium bromide staining. Concentrations (0.5-20 μM) of TQ-Oxime significantly increased cytotoxicity, DNA damage, apoptosis, and iROS, in a concentration-dependent manner compared (p < 0.001). In addition, MMP and GSH levels decreased significantly with increasing concentrations compared with the control (p < 0.001). Overall, these findings contribute to our understanding of the therapeutic potential of TQ and its derivatives in cancer treatment.

Reactions of Alkyl β‐Nitroacrylates with Arenes in Triflic Acid: Synthesis of Oximes of Alkyl 2,3‐Diaryl‐3‐oxopropanoates

AbstractMethyl or ethyl 3‐nitropropenoates (β‐nitroacrylates) AlkO(O)C1−C2H=C3H−NO2 in reaction with arenes ArH in triflic acid CF3SO3H (TfOH) at room temperature in 1 h give rise to oximes of alkyl 2,3‐diaryl‐3‐oxopropanoates AlkO(O)C−CH(Ar)−C(Ar)=NOH in yields of 42–92 %. The obtained oximes bearing ortho‐methyl substituents in the aryl ring exist as atropoisomers in solutions. The study of protonated forms of β‐nitroacrylates by NMR and DFT calculations has revealed that the reactive electrophiles are species AlkO(HO+)C1−C2H=C3H−N+(O)(OH) protosolvated on the acceptor groups NO2 and CO2R. Plausible reaction mechanism is based on the primary interaction of aromatic nucleophiles with these electrophilic species onto their carbon C2.

Direct Synthesis of Aldoximes: Ruthenium Catalyzed Coupling of Alcohols and Hydroxylamine Hydrochloride.

A catalytic method for the direct synthesis of oximes from alcohols and hydroxyl amine hydrochloride salt is reported. The reaction is catalyzed by a ruthenium pincer catalyst, which oxidizes alcohols involving amine-amide metal-ligand cooperation, and the in situ formed aldehydes condense with hydroxyl amine to deliver the oximes. Notably, the reaction requires only a catalyst and base; water and liberated hydrogen are the only byproducts, making this protocol attractive and environmentally benign.

One Pot Synthesis of Oximes from Carbonyl Compounds Catalysed by Vanadium( V) Complex

Background: An eco-friendly catalyst was synthesized in good yield and characterized by various physicochemical techniques. The catalytic performance of the environmentally benign complex was investigated via slurry synthesis of oximes. The catalytic studies were successfully carried out using a simple protocol. The fascinating advantage of this protocol is cost effectiveness, simple work up, good yield, short reactions time, and milder reaction conditions. Methods: The complex was prepared by reaction of vanadium pentoxide with hydrazone ligand in 1:1 molar ratios, and to this reaction mixture, potassium carbonate (0.14 g, 1 mmol) was added and ground till fine yellow colour powder appeared. Oximations were carried out by reacting the substrates, 15 % H2O2, ammonia and vanadium(V) complex. The reaction was taken in a mortar and ground till a fine powder appeared. After completion of the reaction, the crude product was extracted using dichloromethane/water in 1:2, v/v, evaporated and dried under vacuum. Results: We synthesized different varieties of oximes using our newly synthesized complex as a catalyst. The products were characterized by 1H NMR and 13C NMR spectroscopy. The completion of the reaction was monitored by checking the complete disappearance of the aldehyde proton and the appearance of oxime protons. We also grew some single crystals of the products to provide further supporting evidences about the formation of products. Conclusion: Oximation of various carbonyl compounds was prepared quantitatively under the slurry condition, using {[K(H¬2O)3][V(O)2L]}2 as a catalyst. The catalytic reactions can be carried out under mild conditions, with ease of scalability, and straightforward work-up procedure, which makes the present protocols greener and better alternative methods for the synthesis of oximes.

Synthesis of oxime ester‐based epoxy resin with chemical recyclability

AbstractEpoxy, a typical thermosetting resin, exhibits excellent mechanical properties, thermal stability, and chemical resistance. However, it can cause environmental pollution when discarded prior to decomposition. In this study, a novel oxime epoxy based on 1,4‐benzoquinone dioxime was developed. It decomposes quickly under mild conditions and without requiring organic solvents, thus is environmentally friendly. The optimal curing temperature for benzoquinone oxime epoxy (BOE) with a curing agent was 85°C as determined by differential scanning calorimetry. In addition, the tensile strength and Young's modulus of the BOE/1,6‐hexanediamine (HMDA) resin are 20 and 400 MPa, respectively, and Tg is 76°C. Furthermore, thermogravimetric analysis revealed that the BOE resin was thermally stable. Interestingly, BOE/HMDA degraded in 8 h under mild conditions. This rapid degradation will facilitate the development of new chemically degradable epoxy molecules with embedded oximes and provide insights into solving the environmental problems caused by discarded epoxy resin.

Introduction to the Stereoselective Synthesis of Oximes

Introduction to the Stereoselective Synthesis of Oximes

Templating synthesis of oxime/amidoxime functionalized hollow nanospheres by air bubbles generated from “Ouzo-Like” effect for fast and massive uranium uptake

Simple and green synthesis of oxime or amidoxime functionalized hollow sorbents are critical for meeting the demands of highly efficient uranium extraction. To address this, a facile methodology using air bubbles generated from the “Ouzo-Like” effect as templates to synthesize oxime/amidoxime functionalized hollow PDA nanospheres (H-PDA-SO and H-PDA-AO) with fast and massive uranium extraction performances was reported. When 50 mL of Tris solution (0.6 mg mL−1) was mixed with n-propanol (6.25 mL) for 2.0 min, nanobubbles with the mean size of 56.7 nm spilled out, and uniformly sized H-PDA-SO nanospheres with oxime groups (about 250 nm) and H-PDA-AO nanospheres with amidoxime groups (about 150 nm) were simply obtained via self-assembled polydopamine and post-modification around the air/water interface. Owing to the accessible affinity sites and hollow structure, H-PDA-SO and H-PDA-AO displayed high maximum adsorption capacities (103.09 mg g−1 and 331.62 mg g−1 at 298 K) and fast adsorption rate (below 60 min) with high removal efficiency. Under the influence of coexisting ions, H-PDA-SO and H-PDA-AO showed not only a high uranium adsorption capacity but also a more predominant capacity than all the competing ions. Moreover, H-PDA-SO and H-PDA-AO exhibited high stability as well as excellent recyclability toward uranium capture after five regeneration cycles. Surface coordination of oxime/amidoxime sites with uranium was the main binding mechanism, and negative charged O-containing function groups enhance this affinity interactions.

A catalytic regioselective procedure for the synthesis of aryl oximes in the presence of palladium nanoparticles

The synthesis of aryl oximes from aryl aldehyde derivatives was carried out using hydroxylamine hydrochloride and aluminum oxy hydroxide-supported palladium (Pd/AlO(OH) nanoparticles. The procedure is revealed via the regioselective synthesis of oxime derivatives in a polar solvent mixture resulting in high yields at room temperature.

Stereoselective synthesis of oxime containing Pd(II) compounds: highly effective, selective and stereo-regulated cytotoxicity against carcinogenic PC-3 cells.

New palladium compounds [Pd{(1S,4R)-NOH^NH(R)}Cl2] (R = Ph 1a or Bn 1b), [Pd{(1S,4R)-NOH^NH(R)}{(1S,4R)-NO^NH(R)}][Cl] (R = Ph 2a or Bn 2b) and corresponding [Pd{(1R,4S)-NOH^NH(R)}Cl2] (R = Ph 1a' or Bn 1b') and [Pd{(1R,4S)-NOH^NH(R)}{(1R,4S)-NO^NH(R)}][Cl] (R = Ph 2a' or Bn 2b') have been synthesized. Novel compounds 1a, 1b, and 2b (and 1a', 1b', and 2b') were obtained in solution as a mixture of diastereomers whose relative ratios depend on the solvent and the nature of the amino substituent. In contrast, the synthetic reactions of derivatives 2a and 2a' were stereospecific, and afforded single enantiomers of absolute configuration (SN,1SC,4RC)-(RN,1SC,4RC) and (RN,1RC,4SC)-(SN,1RC,4SC), respectively. All compounds have been fully characterized by NMR and IR spectroscopy, time-dependent UV-spectroscopy, ESI-HR-MS in water, and CHN elemental analysis. Absolute configurations of the major epimers of 1a and 1a', both epimers of 1b and enantiomer 2a', were determined by single crystal X-ray crystallography, and confirmed by 2D NOESY NMR experiments in solution. Additionally, the pH-dependent stability of 2b in water was assessed by 1H-NMR spectroscopy. Metal derivatives have been tested in vitro against three human cancer (prostate PC-3, cervical HeLa, and breast MCF-7) cell lines. The highest anticancer activities were shown by palladium compound 2a' in all cancer cells, with IC50 values up to 80 times lower than those found for cisplatin. The cytotoxicity of 2a and 2a'' is stereo-dependent, with IC50 values that differ significantly for each enantiomer in all the cell lines tested. The cytotoxic activity of 2a and 2a' was further evaluated against the non-tumorigenic human prostate RWPE-1 cell line, revealing a selectivity index (SI) of ca. 30 for derivative 2a'. DNA interactions have been investigated by equilibrium dialysis, fluorescence resonance energy transfer (FRET) DNA melting assays, and viscometric titrations, pointing to groove and/or external binding. Cell cycle assay on PC-3 cells after treatment with 2a or 2a' shows cell cycle arrest in the S and G2/M phases, especially when the cells are treated with compound 2a'.

Poly(N-vinylimidazole): A biocompatible and biodegradable functional polymer, metal-free, and highly recyclable heterogeneous catalyst for the mechanochemical synthesis of oximes.

The catalytic activity of poly(N-vinylimidazole), a biocompatible and biodegradable synthetic functional polymer, was investigated for the synthesis of oximes as an efficient, halogen-free, and reusable heterogeneous catalyst. The corresponding oximes were afforded in high to excellent yields at room temperature and in short times using the planetary ball mill technique. Some merits, such as the short reaction times and good yields for poorly active carbonyl compounds, and avoiding toxic, expensive, metal-containing catalysts, and hazardous and flammable solvents, can be mentioned for the current catalytic synthesis of the oximes. Furthermore, the heterogeneous organocatalyst could be easily separated after the reaction, and the regenerated catalyst was reused several times with no significant loss of its catalytic activity.

Photocatalyzed Triplet Sensitization of Oximes Using Visible Light Provides a Route to Nonclassical Beckmann Rearrangement Products.

Oximes are valuable synthetic intermediates for the preparation of a variety of functional groups. To date, the stereoselective synthesis of oximes remains a major challenge, as most current synthetic methods either provide mixtures of E and Z isomers or furnish the thermodynamically preferred E isomer. Herein we report a mild and general method to achieve Z isomers of aryl oximes by photoisomerization of oximes via visible-light-mediated energy transfer (EnT) catalysis. Facile access to (Z)-oximes provides opportunities to achieve regio- and chemoselectivity complementary to those of widely used transformations employing oxime starting materials. We show an enhanced one-pot protocol for photocatalyzed oxime isomerization and subsequent Beckmann rearrangement that enables novel reactivity with alkyl groups migrating preferentially over aryl groups, reversing the regioselectivity of the traditional Beckmann reaction. Chemodivergent N- or O- cyclizations of alkenyl oximes are also demonstrated, leading to nitrones or cyclic oxime ethers, respectively.

Synthesis, biological activities of chalcones and novel 4-acetylpyridine oximes, molecular docking of the synthesized products as acetylcholinesterase ligands

Heterocyclic chalcones were synthesized by reaction of 4-acetylpyridine with the corresponding aromatic aldehydes under Claisen Schmidt conditions. These chalcones were used as starting material for the synthesis of oximes in the presence of hydroxylamine hydrochloride. The structures of the synthesized compounds were confirmed by IR, 1H NMR, 13C NMR and ESI-MS, HRMS spectral analyses. All the synthesized compounds were evaluated for their antioxidant activity by DPPH• method and their in vitro antimicrobial activity by disk diffusion method against two Gram-negative bacteria, one Gram-positive bacteria and two fungal strains (C. albicans and A. niger). The results showed that the synthesized compounds did not display significant antioxidant activity. However, compounds 3b, 3d, 3f, 3h, 3i showed excellent antibacterial activity better than the standard drug against the bacterial strain S. aureus (ATCC 25923). The two compounds 3c, 3d proved very active against the fungal strain A. niger (MIC= 7.81 µg/ mL, 15.62 µg/mL respectively) while the antifungal drug used as reference (Fluconazole) was inactive. Molecular docking and molecular dynamics results revealed that the synthesized compounds, 4e, 4c, and 5j, were involved in a large number of favorable interactions with the active site residues of the acetylcholinesterase protein, which can stabilize the ligands in the active site and increase their affinities.

Dioxido-vanadium(V) complex catalyzed oxidation of alcohols and tandem synthesis of oximes: a simple catalytic protocol for C–N bond formation

We report the synthesis of a vanadium(V) complex characterized by FT-IR and 1H NMR spectroscopy. The structure of the complex was established by single crystal X-ray crystallography. We also carried out the catalytic oxidation of benzyl alcohol, hetero-aryl alcohols and propargylic alcohols. Tandem synthesis of oximes from alcohols were also carried out using our vanadium(V) complex. The newly synthesized complex acts as a catalyst for oxidation reactions and tandem synthesis of oxime from alcohols.

Multicycle adsorption and desorption for recovery of U(VI) from aqueous solution using oxime modified zeolite-A

This paper reports synthesis of oxime modified zeolite-A as an efficient adsorbent for uranium (U(VI)). The as prepared adsorbent was thoroughly characterised and the effect of various experimental parameters were also studied. Maximum adsorption occurs in the pH range of 4–6 with adsorption efficiency of 98%. Adsorption experiment results showed that the equilibrium data fitted well to Langmuir model and follow pseudo second order kinetics. More importantly the spent adsorbent was successfully regenerated and multicycles of adsorption and desorption were showing good efficiency in each run. The material is stable and reusable up to 8 cycles with constant adsorption efficiency. The adsorption capacity of 4.92 mg/g is observed for U(VI) in presence of other competing metal ions which include Cr, Cd, Co, Pb and Mn. It can be inferred from the results that oxime modified zeolite-A is a promising adsorbent for recovery of U(VI) due its easy separation, high adsorption and excellent reusability.

A Synergic Activity of Urea/Butyl Imidazolium Ionic Liquid Supported on UiO-66-NH2 Metal–Organic Framework for Synthesis of Oximes

An efficient supported ionic liquid catalyst is designed for condensation reaction of aldehydes and ketones. The Zr-based metal–organic framework (MOF), UiO-66-NH2, was initially functionalized with N,N′-dibutyl imidazolium ionic liquid (UiO-66-NH2-ILBr–), and then urea was attached to the ionic liquid (IL) to form a task-specific IL. Bromide was exchanged with tetrafluoroborate and the catalyst exhibits excellent performance for the synthesis of oximes. The ionic liquid/urea coupling showed a synergistic effect on the efficiency of the reaction. The supported catalyst system was recycled simply by filtration and reused for five times without significant decrease in its activity. The catalyst was characterized with PXRD, FTIR, TGA, XPS, BET, FE-SEM, EDS, elemental mapping and elemental analysis (CHN). MOF/IL/urea catalytic system was used for the synthesis of oximes

Co/Zn-Grafted Mesoporous Silica Nanoparticles Catalyzed Cyclohexanimine Oxidation under UV Irradiation: High Performance Ozonation Process

A new series of cobalt/zinc-grafted mesoporous silica nanoparticles (CZ-MSN) catalysts were synthesized and characterized using FTIR, SEM, TEM, XRD and nitrogen adsorption-desorption. The molar ratio of Si/Zn was 10 and the amounts of cobalt atom were 1, 3, 5 and 7 wt% (denoted as CZM-X). The nitrogen adsorption/desorption results showed that the surface area increased from 322 in CZM-7 to 408 m2g−1 in CZM-1. The catalytic activity was investigated for the oxidation reaction by cyclohexanone oxime synthesis from cyclohexanimine using ozone gas flow under UV light at room temperature for 20 min. The results showed that the oxidation of cyclohexanimine to cyclohexanone oxime was 98% over CZM-1 and its selectivity was 97%. The catalytic activity decreased with increasing the cobalt atoms as the order of CZM-1 > CZM-3 > CZM-5 > CZM-7 > Zn-MSN > MSN. The significant advantages of using CZM-1 including high conversion and selectivity, low reaction temperature, and short reaction time. This study introduces a new pathway for oxime synthesis with excellent performance.