Rearrangement Of Oximes Research Articles

Insight into Synergistic Brønsted and Lewis Acidic Deep Eutectic Solvent for Beckmann Rearrangement of Cyclohexanone Oxime

ε‐Caprolactam (CPL) is industrially produced by Beckmann rearrangement of cyclohexanone oxime (CHO) under fuming sulfuric acid, resulting in corrosive and environmental issues. Herein, we prepared triethylamine hydrochloride (TEAHC) and ZnCl2 formed deep eutectic solvent (DES) [TEAHC:2ZnCl2] with Brønsted and Lewis acid sites for efficient liquid rearrangement, achieving 100% conversion of CHO and 95.5% yield of CPL at 80 oC for only 1 h. The results show that ZnCl2 in [TEAHC:2ZnCl2] can promote the detachment of proton, which acts as Brønsted acid site combined with another ZnCl2 molecule to synergistically catalyze the reaction. In the Brønsted acid catalyzed process, the nitrogen atom in CHO as reactive site can be readily attacked by the proton to form protonated CHO, which subsequently undergoes rearrangement. By adding ZnCl2 into TEAHC to obtain [TEAHC:2ZnCl2], the formation of ZnCl2‐CHO complex results in a significant reduction in reaction energy barrier through synergistic effect of Brønsted and Lewis acids. Particularly, the fitted reaction kinetics and low activation energy also confirm the rearrangement can occur under low reaction temperature. Thus, the DESs with efficient catalytic performances for ketoxime rearrangements provide a potential method to design active sites for Beckmann rearrangements of oximes under mild reaction conditions.

Green synthesis of nanocellulose supported cu-bionanocomposites and their profound applicability in the synthesis of amide derivatives and controlling of food-borne pathogens

Copper bionanocomposites (CBNCS) were synthesized using Ipomoea carnea- sourced nanocellulose as support via an eco-friendly and cost-effective method. X-ray Diffractometer (XRD) pattern of CBNCS confirmed the octahedral structure of Cu2O, the face-centered cubic (FCC) crystal structure of Cu(0). XRD also revealed the crystal lattice of cellulose II. Surface Electron Microscope (SEM) and Transmission Electron Microscope (TEM) revealed the uniform distribution of copper nanoparticles (Cu NPs) with an average size of 10 nm due to the presence of nanocellulose. X-ray photoelectron spectroscopy (XPS) provided information about the electronic, chemical state and elemental composition of CBNCS. Thermogravimetric Analysis (TGA) showed the thermal stability of CBNCS. CBNCS catalyzed the rearrangement of oximes to primary amides in a very mild condition with a high yield of up to 92 %. CBNCS effectively inhibited the growth of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) with lower minimum inhibitory concentration MIC values. Antioxidant activity and electrical conductivity of CBNCS were also determined.

Silica gel-promoted synthesis of amide by rearrangement of oxime under visible light

Here we report a silica gel-mediated Beckmann rearrangement of oxime to give amide in a simple and efficient way under visible light, using air as the oxidant. The reactions could be carried out without any photo-catalyst or strong acid. Moreover, silica gel could be recycled for five times without significant loss of activity.

Neighboring Group Participation of Nitrogen Cation to Form an Unusual Six-Membered Ring Intermediate During Oxime Rearrangement.

Neighboring group participation involving a 6-membered ring structure is rare, despite the privilege of 6-membered ring transition structures in organic chemistry. We examined the putative role of a 6-membered cyclic intermediate with neighboring group participation of nitrogen cation in syn-migration of peri-ester indanone oximes. Direct observation of a peri-methyl ester-iminylium intermediate in solution by means of 1H NMR supported the existence of the 6-membered cation intermediate. Density functional theory (DFT) calculations also supported the intervention of this intermediate in the rearrangement and indicated that it has a planar structure stabilized by electron delocalization.

BODIPY Photocatalyzed Beckmann Rearrangement and Hydrolysis of Oximes under Visible Light.

A novel, efficient, and mild protocol for rearrangement of oximes to amides or hydrolyzing to ketone/aldehyde using a simple BODIPY dye as a photocatalyst and air as an oxidant via propagation reaction under visible-light irradiation is reported. The triplet excited state of BODIPY played a significant role in the catalytic process. It was found that the various substituted ketoximes, both with electron-withdrawing and electron-donating substituents, afforded the corresponding products with moderate to excellent yields, and the catalytic efficiency was up to 0.01 mol %.

Mild reductive rearrangement of oximes and oxime ethers to secondary amines with hydrosilanes catalyzed by B(C6F5)3

Oximes, its ether derivatives and the corresponding hydroxylamines rearrange to secondary amines when reacted with PhSiH3 and B(C6F5)3 as catalyst. Computations suggest a reduction–rearrangement to be slightly favored over a Beckmann-type sequence.

Computational study of homogenous gold-catalyzed oxime–oxime rearrangement: Balci–Güven rearrangement

Treatment of N-propargylated pyrrole aldoxime derivatives with gold-based catalyst unexpectedly resulted in oxime–oxime rearrangement, which led to ketoximes. This type of reorganization has not been previously observed in the literature and represents a new rearrangement called the Balci–Guven rearrangement. Based on the experimental findings, the proposed mechanistic pathway was studied. Density functional theory calculations employing wb97xd, m062x, and m06 hybrid functional methods were used to locate and discuss the energetics of the intermediates and the transition states of this rearrangement.

From Isocyanides to Iminonitriles via Silver-mediated Sequential Insertion of C(sp3)-H Bond.

SummaryHeterocycles are prevalent constituents of many marketing drugs and biologically active molecules to meet modern medical challenges. Isocyanide insertion into C(sp3)–H bonds is challenging especially for the construction of quaternary carbon centers. Herein, we describe an efficient strategy for the synthesis of α-iminonitrile substituted isochromans and tetrahydroisoquinolines (THIQs) with quaternary carbon centers through silver-triflate-mediated sequential isocyanide insertion of C(sp3)–H bonds, where isocyanide acts as the crucial “CN” and “imine” sources. The produced α-iminonitriles have extensive applications as valuable synthetic building blocks for pharmacologically interesting heterocycles. This protocol could be further applied for the synthesis of iminonitrile-decorated phenanthridines and azapyrene. Interestingly, a remarkable aggregation-induced emission (AIE) effect was first observed for an iminonitrile-decorated pyrene derivative, which may open a particular area for iminonitrile applications in materials science.

Visible Light-Promoted Beckmann Rearrangements: Separating Sequential Photochemical and Thermal Phenomena in a Continuous Flow Reactor.

The Beckmann rearrangement of oximes to amides typically requires strong acids or highly reactive, hazardous electrophiles and/or elevated temperatures to proceed. A very attractive alternative is the in situ generation of Vilsmeier–Haack reagents, by means of photoredox catalysis, as promoters for the thermal Beckmann rearrangement. Investigation of the reaction parameters for this light‐induced method using a one‐pot strategy has shown that the reaction is limited by the different temperatures required for each of the two sequential steps. Using a continuous flow reactor, the photochemical and thermal processes have been separated by integrating a flow photoreactor unit at low temperature for the electrophile generation with a second reactor unit, at high temperature, where the rearrangement takes place. This strategy has enabled excellent conversions and yields for a diverse set of oximes, minimizing the formation of side products obtained with the original one‐pot method.

Recyclable Polymer-Supported Terpyridine–Palladium Complex for the Tandem Aminocarbonylation of Aryl Iodides to Primary Amides in Water Using NaN3 as Ammonia Equivalent

Primary aromatic amides are valuable compounds, which are generally prepared via Beckmann rearrangement of oximes and the hydration of nitriles in organic solvents. We investigated the environmentally friendly catalytic aminocarbonylation in water. Thus, a novel heterogeneous transition-metal catalyst, a polymer-supported terpyridine–palladium(II) complex, was prepared and found to promote azidocarbonylation of aryl iodides with NaN3 and to reduce the generated benzoyl azides in water under CO gas to yield primary aryl amides with high to excellent yield in a one-pot reaction. The catalyst was recovered and reused several times with no loss of catalytic activity.

ChemInform Abstract: Oxime‐Derived Palladacycles: Applications in Catalysis

AbstractReview: catalytic activity of oxime‐derived palladacycles for alkenylation, cross‐coupling, alkynylation, carbonylation, annulation, α‐arylation, C—H activation, and oxime rearrangement reactions as well as their role as metalloenzymes in hydrolytic processes along with other applications in organic synthesis; 117 refs.

Gold-catalyzed oxime-oxime rearrangement.

The gold-catalyzed reaction of pyrrole and indole oximes having a propargyl group attached to the nitrogen atom was studied. The selective 6-endo-dig mode of cyclization was observed for the terminal alkynes giving rise to the formation of pyrazine N-oxides in the presence of a gold catalyst. However, the reaction with substituted alkyne transferred the oxime functionality intramolecularly from one carbon atom to another via the 7-endo-dig cyclization process. This transformation is unprecedented in the literature and is named an oxime-oxime rearrangement.

Low Environmental Load Process for the Beckmann Rearrangement of Cycloalkanone Oximes by Brønsted Acid Catalyst with Cobalt Salts

Beckmann rearrangements of oximes to lactams often require harsh conditions and/or the use of large amounts of acid catalyst. To reduce the amount of Bronsted acid required, and to avoid the formation of a large amount of undesirable byproducts under mild reaction conditions, a low environmental load process was developed. Beckmann rearrangements of cyclohexanone oxime and cyclooctanone oxime were achieved using a combination of a Bronsted acid and cobalt tetra-fluoroborate hexahydrate. Various Bronsted acid catalysts (10 - 20 mol%) were used to obtain the corresponding lactams in high yields at 80℃.

Computational and ¹³C investigations of the diazadienes and oxazadienes formed via the rearrangement of methylenecyclopropyl hydrazones and oximes.

Computational and further experimental investigations of the previously reported diazadienes, obtained via the rearrangement of methylenecyclopropyl hydrazone 1 are reported. Calculations at the CCSD(T)/cc-pVTZ//B3LYP/6-31G(d) level of theory indicate that the initially reported product 3 would, if formed, undergo rapid electrocyclic ring opening and, hence, would be unstable under the reaction conditions. Based on this computational prediction, further analysis of the (13)C NMR spectrum, previously attributed to 3, led to the revision of structure 3 to that of its N-tosylaminopyrrole constitutional isomer 11. Similarly, structure 8, formed in the rearrangement of oxime 6, was revised to that of N-hydroxypyrrole 12.

ChemInform Abstract: Rearrangement of Oximes and Hydroxylamines with Aluminum Reductants

AbstractReview: 72 refs.

Green production technology of caprolactam

Ideal of green chemistry is the reaction of economy and production of environment-friendly green products. This requires that every atom in the raw materials would transfer into the production, no production is of waste and by-products, and no usage of the poisonous and harmful materials. Practice the concept of green chemistry, Research Institute of Petroleum Processing successfully developed the green caprolactam production technology, to construct 200 kt/a plant. The innovation technology includes: TS-1 zeolite integration with single-vessel continuous slurry bed for cyclohexanone ammoximation; silicalite-1 zeolite integration with moving bed for cyclohexanone oxime rearrangement, and amorphous Ni alloy integration with magnetically stabilized bed for purification of caprolactam. Based on the commercial application results, the caprolactam production plant investment decrease 70%, operation costs decrease 10%, atom utilization rate increases to 90% from 60%, and essentially waste-free, respectively. Green caprolactam production technology produces great economic and social benefits, practices green chemistry concepts, and be a successful example of green chemistry.

Beckmann rearrangement of oxime obtained from oleanolic acid. Structure elucidation of the initial oxime

Seven-membered A-lactam and A-nitrile of methyl oleanolate were synthesized from the corresponding oxime. Many reaction setups were tried to find the optimum conditions. The best results (the highest yield of the desired lactam along with total consumption of starting oxime) were obtained in pyridine with phosphoryl chloride as Lewis acid. The main product was obtained with the yield of about 60%. Mechanism of Beckmann rearrangement for the above triterpenic 3-oxime leading to normal and abnormal product (a lactam and a nitrile, respectively) was explained. The structures of both products were determined and fully characterized by spectral data. The stereoisomerism of the initial oxime was determined on the basis of Beckmann rearrangement product structure and X-ray analysis.

ChemInform Abstract: A One‐Pot Approach to Δ2‐Isoxazolines from Ketones and Arylacetylenes.

AbstractThe process involves at least five separate mechanistic steps: addition of ketones to arylacetylenes, oximation of the resulted β,γ‐unsaturated ketones, E→Z isomerization of the oximes (for oximes of alkyl‐ and cycloalkyl ketones), prototropic rearrangement of oximes of β,γ‐unsaturated ketones to oximes of α,β‐unsaturated ketones, and their final cyclization.

ChemInform Abstract: Reaction of Oximes of α‐Diketones with Diphosphorous Tetraiodide for Preparation of Oxadiazoles and Nitriles.

AbstractDiphosphorous tetraiodide is used as mild agent for the simple dehydration of oximes to 1,2,5‐oxadiazole (IV), (VI), (VIII) as well as the rearrangement of oximes to normal Beckmann product 1,2,4‐oxadiazole (II).

Reaction of Oximes of α-Diketones with Diphosphorous Tetraiodide for Preparation of Oxadiazoles and Nitriles

The utility of diphosphorous tetraiodide as a new, mild, condensing agent for synthesis of oxadiazole is described. These data indicate the simple dehydration of oximes to 1,2,5-oxadiazole as well as the rearrangements of oximes to normal Beckmann product 1,2,4-oxadiazole. However, mono-oxime of benzil undergoes abnormal Beckman rearrangement to benzaldehyde as major product. The described method is simple and important for the synthesis of the oxadiazoles as well as for nitriles.