Reaction Of Oximes Research Articles

Photochemical radical cyclization reactions with imines, hydrazones, oximes and related compounds.

Photochemical reactions are a key method to generate radical intermediates. Often under these conditions no toxic reagents are necessary. During recent years, photo-redox catalytic reactions considerably push this research domain. These reaction conditions are particularly mild and safe which enables the transformation of poly-functional substrates into complex products. The synthesis of heterocyclic compounds is particularly important since they play an important role in the research of biologically active products. In this review, photochemical radical cyclization reactions of imines and related compounds such as oximes, hydrazones and chloroimines are presented. Reaction mechanisms are discussed and the structural diversity and complexity of the products are presented. Radical intermediates are mainly generated in two ways: (1) electronic excitation is achieved by light absorption of the substrates. (2) The application of photoredox catalysis is now systematically studied for these reactions. Recently, also excitation of charge transfer complexes has been studied in this context from many perspectives.

Intramolecular iron-catalyzed transannulation of furans with O-acetyl oximes: synthesis of functionalized pyrroles

Intramolecular iron(iii)-catalyzed reaction of furyl-tethered O-acetyl oximes yields substituted pyrroles through electrophilic 5-exo-trig ipso-addition of nitrogen to the furan ring.

Iminyl radical initiated sulfonylation of alkenes with rongalite under photoredox conditions

A photoredox-catalyzed reaction of oximes, rongalite and electrophiles is accomplished, affording pyrrole-substituted aliphatic sulfones or sulfonamides in moderate to good yields.

Synthesis of Isoxazolylvinyl Ketones from Substituted Furans

A new method for the preparation of isoxazolylvinyl ketones related to potential cytotoxic agents has been developed. In the first step, the reaction of furfuryl ketones with hydroxylamine hydrochloride affords the corresponding oximes. Further, the oxidative ring opening – ring closure reaction of oximes leads to isoxazoles with an α, β-unsaturated carbonyl motif. The developed procedure is metal-free and does not require expensive starting materials.

Exo-Cyclization: Intermolecular Methylene Transfer Sequence in Au-Catalyzed Reactions of O-Homopropargylic Oximes.

The Au-catalyzed reactions of O-homopropaylic oximes afforded the 3-alkenylated isoxazolines in good to high yields. The mechanistic studies suggest that the reaction proceeds through an exo-cyclization followed by intermolecular methylene group transfer. In addition, oligomeric species of the starting material were observed in the reaction mixture by mass spectra, supporting our proposed mechanism, which proceeds through a repeated intermolecular C-C bond forming process.

A stability study of carbonyl compounds in Tedlar bags by a fabricated MEMS microreactor approach

The analysis of volatile organic compounds (VOCs) in exhaled breath has a great potential as a noninvasive approach for early detection of lung cancer and other diseases. The stability of VOCs in sampling bags significantly affects quantification of target VOCs in exhaled breath. Carbonyl compounds are a subset of VOCs in exhaled breath and are more reactive than other VOCs in breath matrix. This work reports the stability of carbonyl compounds in exhaled breath collected in Tedlar bags. A silicon microreactor coated with 2-(aminooxy)ethyl-N, N, N trimethylammonium iodide (ATM) was used for chemoselective trapping trace carbonyl compounds in exhaled breath samples by means of oximation reactions. ATM-carbonyl adducts were measured using an ultra-high-performance liquid-chromatography-mass spectrometry (UHPLC-MS). The results indicate that breath samples stored at ambient temperature can recover more than 80% of carbonyl compounds if the samples are processed within one hour. The recovery percentages of unsaturated aldehydes are much lower than that of saturated carbonyl compounds. The storage of breath samples at cold temperature (4 °C) can reduce degradation of carbonyl compounds. The recovery percentages of carbonyl compounds in breath samples of current smokers are slightly lower than that of nonsmokers.

Catalytic Asymmetric Synthesis of Atropisomeric Nitrones: Versatile Intermediate for Axially Chiral Biaryls.

A Cu-catalyzed asymmetric ring-opening reaction of five-membered diaryliodonium salts and oximes is introduced. The reactions undergo selective N-arylation of oximes and provide an efficient protocol for the synthesis of atropisomeric nitrones. The optically active nitrones, serving as versatile intermediates, were converted to diversely functionalized axially chiral aniline derivatives and N-heterocycles.

Poly(hydroxamic acid) ligand from palm‐based waste materials for removal of heavy metals from electroplating wastewater

AbstractHeavy metals pollutants are nonbiodegradable and their bioaccumulation results in detrimental environmental consequences. Therefore, it is important to effectively remove toxic heavy metal waste from industrial sewage. Thus, the main goal of this research is to synthesize an ideal cellulose‐based adsorbent from palm‐based waste materials (agro waste) in order to be utilized in real‐life practical applications with low cost as such removing common toxic heavy metals from industrial effluents. A poly(methyl acrylate) grafted palm cellulose was synthesized via a free‐radical initiation process, followed by an oximation reaction to yield poly(hydroxamic acid) ligands. The adsorption capacity (qe) of poly(hydroxamic acid) ligands for metal ions such as copper (Cu2+), iron (Fe3+), and lead (Pb2+) were 325, 220, and 300 mg g−1, respectively at pH 6. In addition, the X‐ray photoelectron spectrometry results are to be proved the binding of metal ions, for instance, Cu(II) ions showed typically significant BEs of 932.7 and 952.0 eV corresponding to the Cu2p3/2 and Cu2p1/2 species. The heavy metal ions adsorption followed a pseudo‐first‐order kinetic model pathway. The adsorption capacity (qm) is also derived from the Langmuir isotherm linear plot, which does not showed good correction coefficients. However, the results were correlated to the Freundlich isotherm model, where the R2 value showed significance (>0.98), indicating that multiple layer adsorption occurs on the synthesized ligand. The synthesized polymeric ligand is an excellent adsorbent for the removal of heavy metals from the industrial wastewater. In addition, the metal analysis results showed that about 98% removal of copper and iron ions from electroplating wastewater including lead, nickel, and chromium can be removed up to 85–97%.

Poly(amidoxime) ligand derived from waste palm fiber for the removal of heavy metals from electroplating wastewater.

A waste material known as palm oil empty fruit bunch (EFB) is used as a source of cellulose for the development of polymeric materials for the removal of metal ions from industrial wastewater. A poly(acrylonitrile)-grafted palm cellulose copolymer was synthesized by a conventional free radical initiating process followed by synthesis of a poly(amidoxime) ligand by oximation reaction. The resulting products were characterized by FT-IR, FE-SEM, EDX, TGA, DSC, and XPS. The poly(amidoxime) ligand was used to coordinate with and extract a series of transition metal ions from water samples. The binding capacity (qe) of the ligand with the metal ions such as copper, iron, cobalt, nickel, and lead were 260, 210, 168, 172, and 272 mg g-1, respectively at pH 6. The adsorption process followed the pseudo-first-order kinetic model (R2 > 0.99) and as well as the Freundlich isotherm model (R2 > 0.99) indicating the occurrence of a multi-layer adsorption process in the amidoxime ligand adsorbent. Results from reusability studies show that the ligand can be recycled for at least 10 cycles without any significant losses to its initial adsorption capacity. The synthesized polymeric ligand was shown to absorb heavy metals from electroplating wastewater with up to 95% efficiency.

Brønsted Acid and H-Bond Activation in Boronic Acid Catalysis.

Boronic acid catalysis has emerged as a mild method for promoting a wide variety of reactions. It has been proposed that the mode of catalysis involves Lewis acid or covalent activation of hydroxyl groups by boron, but limited mechanistic evidence exists. In this work, representative boronic acid catalyzed reactions of alcohols and oximes have been reinvestigated. A series of control experiments with boronic and Brønsted acids were interpreted along with correlations between their reactivity and their acidity measured by the Gutmann-Beckett method. Overall, it was concluded that the major modes of catalysis involve either dual H-bond catalysis or Brønsted acid catalysis. Strong Brønsted acids were shown to be generated in situ from covalent assembly of the boronic acids with hexafluoroisopropanol, explaining why the solvent had such a major impact on the reactivity. This new insight should guide the future development of boronic acid catalysis, where the diverse and solvent-specific nature of catalytic modes has been overlooked.

Variability of Rhodium(III)-Catalyzed Reactions of Aromatic Oximes with Alkenes

Acetophenone oxime reacts with various alkenes in the presence of the rhodium catalyst [Cp*RhCl2]2 (2.5 mol%; Cp* = pentamethylcyclopentadienyl) and 1,1,1,3,3,3-hexafluoropropan-2-ol as an important cosolvent. Styrene, aliphatic terminal alkenes, and strained cyclic alkenes gave the corresponding substituted dihydroisoquinolines in yields of 50–99%. On the other hand, alkenes containing functional groups close to the double bond gave a variety of different products. The reactions of acetophenone oxime with styrene or dec-1-ene in the presence of the chiral catalyst [(C5H2 t Bu2CH2 t Bu)RhI2]2 provided the corresponding dihydroisoquinolines with improved regioselectivity but a low enantiomeric ratio (61:39 in both cases).

Design, synthesis, brine shrimp lethality and cytotoxicity of some novel 17a-aza-D-homo-androster-17-one derivatives

In this work, twenty-eight novel 17a-aza-D-homo-androster-17-one derivatives, which divided into two categories, were synthesized with commercial available starting material (dehydroepiandrosterone) via oximation reaction, Beckmann rearrangement, hydroxyl protection, N-alkylation and deprotection. All compounds were characterized by 1H NMR, 13C NMR and HRMS. The structure of 14 g was also identified by X-ray single crystal diffraction. The bioactivities, brine shrimp toxicity and cytotoxicity, of all derivatives were tested. The results indicated that compounds 11 h, 11i, 11 m, 11 s, 14 b and 14 g exhibited excellent toxicity against brine shrimp with LC50 values ranging from 5.34 to 16.89 μg/mL, and compounds 11 s and 14 g displayed significant cytotoxicity against HT29 cells and A549 cells with IC50 values of 9.70 μM and 8.85 μM, respectively. Structure-activity relationships are discussed based on the results obtained from our research, and some important determinants for further modification of steroids towards the development of novel drug candidates are identified.

SYNTHESIS OF 2-[2-(HYDROXYIMINO)ALKYL]-1,2-OXAZOL-5(2 Н )-ONES

The reaction of α-hydroxyamino oximes with ethyl acetoacetate and ethyl α-methylacetoacetate yields 2-[2-(hydroxyimino)alkyl]-1,2-oxazol-5(2 H )-ones. In the reaction of alkylaromatic α-hydroxyamino oximes with ethyl acetoacetate, the intermediate imidazo[1,2- b ][1,2]oxazolones were isolated, which then convert to the target compounds. Authors: Elena B. Nikolaenkova, Irina Yu. Bagryanskaya, Alexsei Ya. Tikhonov*

Oximation reaction induced reduced graphene oxide gas sensor for formaldehyde detection

High-performance gas sensors can offer great potentials for monitoring and detection of volatile organic compounds (VOCs) in both domestic and industrial environment. In the present work, a new HCHO gas sensor was constructed with reduced graphene oxide (RGO) induced by the oximation reaction. The gas-sensing performance test results suggested that the RGO hydroxylamine hydrochloride (RGO/HA-HCl) sensor presented a high response of 75% at 16 ppm HCHO at room temperature, and a high selectivity for HCHO suffering little interference with high concentrations of volatile organic compounds, including methanol, ethanol, and methylbenzene, dichloromethane and water. Additionally, the RGO/HA-HCl sensor also showed a good long-term stability with RSD of 5.83% for a 15-day continuous sensing test, and the detection limit (DL) could reach 0.023 ppm under ambient conditions. Moreover, the mechanism for the high sensitivity and selectivity of formaldehyde was further established by in-situ gas chromatography mass spectrometry (GC–MS). This work would provide a reliable new HCHO gas sensor which could be used for monitoring and forewarning the emission of HCHO for a better protection and improvement of our environment.

P-Trifluoroacetophenone Oxime Ester Derivatives: Synthesis, Antimicrobial and Cytotoxic Evaluation and Molecular Modeling Studies

Background: Azole antifungals are among the first-line drugs clinically used for the treatment of systemic candidiasis, a deadly type of fungal infection that threatens mostly immunecompromised and hospitalized patients. Some azole derivatives were also reported to have antiproliferative effects on cancer cells. Objective: In this study, 1-(4-trifluoromethylphenyl)-2-(1H-imidazol-1-yl)ethanone (3), its oxime (4), and a series of its novel oxime ester derivatives (5a-v) were synthesized and tested for their in vitro antimicrobial activities against certain ATCC standard strains of Candida sp. fungi and bacteria. The compounds were also tested for their cytotoxic effects against mouse fibroblast and human neuroblastoma cell lines. Molecular modeling studies were performed to provide insights into their possible mechanisms for antifungal and antibacterial actions. Methods: The compounds were synthesized by the reaction of various oximes with acyl chlorides. Antimicrobial activity of the compounds was determined according to the broth microdilution method. For the determination of cytotoxic effect, we used MTS assay. Molecular docking and QM/MM studies were performed to predict the binding mechanisms of the active compounds in the catalytic site of C. albicans CYP51 (CACYP51) and S. aureus flavohemoglobin (SAFH), the latter of which was created via homology modeling. Results: 5d, 5l, and 5t showed moderate antifungal activity against C. albicans, while 3, 5c, and 5r showed significant antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa. Most of the compounds showed approximately 40-50% inhibition against the human neuroblastoma cells at 100 µM. In this line, 3 was the most potent with an IC50 value of 82.18 μM followed by 5a, 5o, and 5t. 3 and 5a were highly selective to the neuroblastoma cells. Molecular modelling results supported the hypothesis that our compounds were inhibitors of CAYP51 and SAFH. Conclusion: This study supports that oxime ester derivatives may be used for the development of new antimicrobial and cytotoxic agents.

Synthesis of 2-[2-(hydroxyimino)alkyl]-1,2-oxazol-5(2Н)-ones

The reaction of α-hydroxyamino oximes with ethyl acetoacetate and ethyl α-methylacetoacetate yields 2-[2-(hydroxyimino)alkyl]-1,2-oxazol-5(2H)-ones. In the reaction of alkylaromatic α-hydroxyamino oximes with ethyl acetoacetate, the intermediate imidazo[1,2-b]-[1,2]oxazolones were isolated, which then convert to the target compounds.

Three new heterometallic ZnII–LnIII complexes with a windmill-like framework and field-induced SMM behavior

We have prepared three 3d–4f heterometallic complexes by the reaction of o-vanillin oxime (H2L) with Zn(NO3)2·6H2O and Ln(NO3)3·6H2O salts in the presence of triethylamine.

Synthesis and Antibacterial Activity of New Acridone Derivatives Containing an Isoxazoline Fragment

A method was developed for the preparation of N-(4-R-4,5-dihydroisoxazol-5-yl)methylacridones by the reaction of aromatic aldehyde oximes with allyl acridones. For the obtained compounds, a high inhibitory activity in relation to test strains of pathogenic microorganisms was revealed, exceeding furacilin.

A copper-catalyzed insertion of sulfur dioxide via radical coupling

A copper-catalyzed three-component reaction of O-acyl oximes, DABCO·(SO2)2, and 2H-azirines under mild conditions has been achieved. This protocol provides an efficient route for the construction of various tetrasubstituted β-sulfonyl N-unprotected enamines in moderate to good yields with excellent stereoselectivity and regioselectivity. Notably, this method represents a rare example of 2H-azirines as useful synthons for β-functionalized N-unprotected enamines. Preliminary mechanistic studies indicate that the reaction proceeds through coupling of a sulfonyl radical and α-carbon radical via copper-catalyzed ring-opening C-C bond cleavage of O-acyl oxime and C-N bond cleavage of 2H-azirine with the insertion of sulfur dioxide.

Ultrafast Oxime Formation Enables Efficient Fluorescence Light-up Measurement of DNA Base Excision.

DNA glycosylases constitute a biologically and biomedically important group of DNA repair enzymes responsible for initiating base excision repair (BER). Measuring their activities can be useful for studying the mechanisms DNA damage and repair and for practical applications in cancer diagnosis and drug screening. Previous fluorescence methods for assaying DNA glycosylases are often complex and/or limited in scope to a single enzyme type. Here we report a universal base excision reporter (UBER) fluorescence probe design that implements an unprecedentedly rapid oxime reaction (>150 M-1 s-1) with high specificity for the abasic (AP) site of DNA. The molecular rotor design achieves a robust >250-500-fold increase in fluorescence upon reaction with AP sites in DNA. By using the fluorescence reporter in concert with specific DNA lesion-containing substrates, the UBER probe can be used in a coupled assay in principle with any DNA glycosylase. We demonstrate the utility of the UBER probe by assaying five different glycosylases in real time as well as profiling glycosylase activity in cell lysates. We anticipate that the UBER probe will be of considerable utility to researchers studying DNA repair biology owing to its high level of generalizability, ease of use, and compatibility with biologically derived samples.