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Electrochemical Synthesis of Isoxazolines: Method and Mechanism.

ABSTRACT: An electrochemical method for the green and practical synthesis of a broad range of substituted isoxazoline cores is presented. Both aryl and more challenging alkyl aldoximes are converted to the desired isoxazoline in an electrochemically enabled regio- and diastereoselective reaction with electron-deficient alkenes. Additionally, in-situ reaction monitoring methods compatible with electrochemistry equipment have been developed in order to probe the reaction pathway. Supporting analyses from kinetic (time-course) modelling and density functional theory support a stepwise, radical-mediated mechanism, and discounts hypothesised involvement of closed shell [3+2] cycloaddition pathways.

SUBMITTER: Holman SDL

PROVIDER: S-EPMC9303936 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Acyclic nitronate olefin cycloaddition (ANOC): regio- and stereospecific synthesis of isoxazolines.

Project description:We report the first demonstrations of intra- and intermolecular acyclic nitronate olefin cycloaddition (ANOC) reactions that enable the highly efficient syntheses of isoxazolines bearing various functional groups. This general approach to accessing γ-lactone fused isoxazolines was hitherto unprecedented. The room temperature transformations reported herein exhibit wide substrate scopes, as evidenced by more than 70 examples, including the generation of five tricyclic isoxazolines. The robustness of this methodology was confirmed by a series of trials that afforded highly functionalized isoxazolines. Both experimental results and density functional theory calculations indicate that these transformations proceed via the in situ formation of acyclic nitronates together with concerted [3+2] cycloaddition and tert-butyloxy group elimination processes to give regio- and stereospecificity.

| S-EPMC8178991 | biostudies-literature

Synthesis and Investigation of Novel Spiro-isoxazolines as Anti-Cancer Agents.

Project description:A series of structurally diverse 4-bromo spiro-isoxazolines possessing a variety of aromatic and aliphatic substituents at the 3 position, were synthesized through a 1,3-dipolar cycloaddition followed by intramolecular cyclization of a pendant hydroxyl or carboxylic acid group. The biochemical antiproliferative activity was evaluated in vitro by using two breast cancer cell lines (MCF-7 and MDA-MB-231) and two prostate cancer cell lines (PC-3 and DU-145) using the MTT viability assay, and the IC50 values were obtained. Spiro-isoxazoline derivatives bearing a p-chloro or an o-dichloro aromatic substituent at the 3-position of the isoxazoline showed considerable antitumor activities in all four cell lines with IC50 value ranging from 43μM to 56μM.

| S-EPMC4371604 | biostudies-literature

Synthesis and antifungal activity of novel pyrazolines and isoxazolines derived from cuminaldehyde.

Project description:Two series of novel cuminaldehyde derivatives containing pyrazoline and isoxazoline moieties have been designed and synthesized. All of the compounds were characterized via 1H-NMR,13C-NMR, and HRMS. The antifungal activities were evaluated against six plant-pathogenic fungi. 3-(2-Fluorophenyl)-5-(4-isopropylphenyl) isoxazoline (2d) and 1-acetyl-3-(2-fluorophenyl)-5-(4-isopropylphenyl)-2-pyrazoline (3d) displayed higher antifungal activities than commercial fungicides against Sclerotinia sclerotiorum, Physalospora piricola and Pyricularia oryzae. The title compounds (2d and 3d) with strong antifungal activities are worth being further evaluated in vivo and in the field.

| S-EPMC6718356 | biostudies-literature

A one-pot synthesis of 3-trifluoromethyl-2-isoxazolines from trifluoromethyl aldoxime.

Project description:Functionalized 3-trifluoromethyl-2-isoxazolines and 3-trifluoromethylisoxazoles were easily prepared from trifluoromethyl aldoxime 2 under mild conditions by using DIB as oxidant. Theoretical studies of the reactivity of trifluoroacetonitrile oxide 4 toward olefins and alkynes were carried out. The 3-trifluoromethyl-2-isoxazolines were ring-opened with NaBH4 and NiCl2 to yield the corresponding trifluoromethylated γ-amino alcohols.

| S-EPMC3869255 | biostudies-literature

Simple Synthesis of Large Graphene Oxide Sheets via Electrochemical Method Coupled with Oxidation Process.

Project description:In this paper, we report a simple two-step approach for the synthesis of large graphene oxide (GO) sheets with lateral dimensions of ≈10 μm or greater. The first step is a pretreatment step involving electrochemical exfoliation of graphite electrode to produce graphene in a mixture of H2SO4 and H3PO4. The second step is the oxidation step, where oxidation of exfoliated graphene sheets was performed using KMnO4 as the oxidizing agent. The oxidation was carried out for different times ranging from 1 to 12 h at ∼60 °C. Prepared GO batches were characterized using a number of spectroscopy and microscopy techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), and UV-visible spectroscopy. Raman and thermogravimetric analysis techniques were used to study the degree of oxidation in the as-synthesized GO batches. The UV-visible absorption spectrum showed an intense peak at 230 nm and an adjacent band at 300 nm corresponding to π-π* and n-π* transitions in all samples. Normalized FTIR plots were used to calculate the relative percentages of oxygen-containing functional groups, which were found to be maximum in GO (6 h). Boehm titration was used to quantify the functional groups present on the GO surface. Overall GO sheets obtained after 6 h of oxidation, GO (6 h), were found to be the best. XRD pattern of GO (6 h) revealed a characteristic peak at 2θ = 8.88°, with the corresponding interplanar spacing between the layers being 0.995 nm, which is among the best with respect to the previous methods reported in the literature. Raman spectroscopy showed that the degree of defect (I D/I G) area ratio for GO (6 h) was 1.24, which is higher than that obtained for GO (1.18) prepared by widely used Marcano's approach.

| S-EPMC6645570 | biostudies-literature

Biphasic electrochemical peptide synthesis.

Project description:The large amount of waste derived from coupling reagents is a serious drawback of peptide synthesis from a green chemistry viewpoint. To overcome this issue, we report an electrochemical peptide synthesis in a biphasic system. Anodic oxidation of triphenylphosphine (Ph3P) generates a phosphine radical cation, which serves as the coupling reagent to activate carboxylic acids, and produces triphenylphosphine oxide (Ph3P[double bond, length as m-dash]O) as a stoichiometric byproduct. In combination with a soluble tag-assisted liquid-phase peptide synthesis, the selective recovery of desired peptides and Ph3P[double bond, length as m-dash]O was achieved. Given that methods to reduce Ph3P[double bond, length as m-dash]O to Ph3P have been reported, Ph3P[double bond, length as m-dash]O could be a recyclable byproduct unlike byproducts from typical coupling reagents. Moreover, a commercial peptide active pharmaceutical ingredient (API), leuprorelin, was successfully synthesized without the use of traditional coupling reagents.

| S-EPMC8513919 | biostudies-literature

Design, Synthesis and Evaluation of Novel Isoxazolines/Oxime Sulfonates of 2'(2',6')-(Di)Chloropodophyllotoxins as Insecticidal Agents.

Project description:A series of 2'(2',6')-(di)halogeno-isoxazolopodophyllic acids-based esters, and oxime sulfonates of 2'(2',6')-(di)halogenopodophyllones were prepared by structural modifications of podophyllotoxin as insecticidal agents against Mythimna separata Walker. It was found that when 2'(2',6')-(di)halogenopodophyllones or 2'(2',6')-(di)chloropicropodophyllones reacted with hydroxylamine hydrochloride, the desired products were related with the configuration of their lactones. Three key single-crystal structures of Ie, IIe and IIIb were determined by X-ray diffraction. Especially compounds IIc and Vc showed the highest insecticidal activity. Moreover, some interesting results of structure-insecticidal activity relationships of tested compounds were also observed.

| S-EPMC5036094 | biostudies-literature

Ultrasound-assisted one-pot three-component synthesis of new isoxazolines bearing sulfonamides and their evaluation against hematological malignancies.

Project description:In the present study, following a one-pot two-step protocol, we have synthesized novel sulfonamides-isoxazolines hybrids (3a-r) via a highly regioselective 1,3-dipolar cycloaddition. The present methodology capitalized on trichloroisocyanuric acid (TCCA) as a safe and ecological oxidant and chlorinating agent for the in-situ conversion of aldehydes to nitrile oxides in the presence of hydroxylamine hydrochloride, under ultrasound activation. These nitrile oxides could be engaged in 1,3-dipolar cycloaddition reactions with various alkene to afford the targeted sulfonamides-isoxazolines hybrids (3a-r). The latter were assessed for their antineoplastic activity against model leukemia cell lines (Chronic Myeloid Leukemia, K562 and Promyelocytic Leukemia, HL-60).

| S-EPMC8436160 | biostudies-literature

The "Green" Electrochemical Synthesis of Periodate.

Project description:High-grade periodate is relatively expensive, but is required for many sensitive applications such as the synthesis of active pharmaceutical ingredients. These high costs originate from using lead dioxide anodes in contemporary electrochemical methods and from expensive starting materials. A direct and cost-efficient electrochemical synthesis of periodate from iodide, which is less costly and relies on a readily available starting material, is reported. The oxidation is conducted at boron-doped diamond anodes, which are durable, metal-free, and nontoxic. The avoidance of lead dioxide ultimately lowers the cost of purification and quality assurance. The electrolytic process was optimized by statistical methods and was scaled up in an electrolysis flow cell that enhanced the space-time yields by a cyclization protocol. An LC-PDA analytical protocol was established enabling simple quantification of iodide, iodate, and periodate simultaneously with remarkable precision.

| S-EPMC7317427 | biostudies-literature

Electrochemical synthesis of urea on MBenes.

Project description:Urea is an important raw material in the chemical industry and is widely used as a nitrogen source in chemical fertilizers. The current industrial urea synthesis not only requires harsh reaction conditions, but also consumes most of the NH3 obtained through artificial synthesis. The conversion of N2 and CO2 into urea through electrochemical reactions under ambient conditions represents a novel green urea synthesis method. However, the large-scale promotion of this method is limited by the lack of suitable electrocatalysts. Here, by means of density functional theory computations, we systematically study the catalytic activity of three experimentally available two-dimensional metal borides (MBenes), Mo2B2, Ti2B2, and Cr2B2 toward simultaneous electrocatalytic coupling of N2 and CO2 to produce urea under ambient conditions. According to our results, these three MBenes not only have superior intrinsic basal activity for urea formation, with limiting potentials ranging from -0.49 to -0.65 eV, but also can significantly suppress the competitive reaction of N2 reduction to NH3. In particular, 2D Mo2B2 and Cr2B2 possess superior capacity to suppress surface oxidation and self-corrosion under electrochemical reaction conditions, rendering them relatively promising electrocatalysts for urea production. Our work paves the way for the electrochemical synthesis of urea.

| S-EPMC8253759 | biostudies-literature

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