Reaction Of Oximes Research Articles

1,3- versus 1,4-[ π4+ π2] Cycloadditions between methyl glyoxylate oxime and cyclopentadiene or cyclopentene

The acid catalyzed cycloaddition reaction of methyl glyoxylate oxime with cyclopentadiene (CPD) afforded the corresponding aza-Diels–Alder adducts, the endo and exo isomers of (±)-methyl 2-hydroxy-2-azabicyclo[2.2.1]hept-5-ene-3-carboxylates, and as the major product a 1,3-cycloadduct, methyl (1 RS,4 RS,5 RS)-(2-oxa-3-azabicyclo[3.3.0]oct-7-ene)-4-carboxylate. The similar reaction using cyclopentene (CP) provided only the 1,3-cycloadduct methyl (1 SR,4 RS,5 SR)-(2-oxa-3-azabicyclo[3.3.0]octane)-4-carboxylate. The influence of various parameters on the reaction outcome was studied and, based on the results obtained, a mechanism for the formation of both 1,3- and 1,4-cycloadducts is proposed. The structure of all adducts was confirmed by NMR spectroscopic data and/or by X-ray crystallography.

Silylboranes as New Sources of Silyl Radicals for Chain‐Transfer Reactions

Various silylboranes, which were outfitted with a catecholborane moiety at one end and a (Me(3)Si)(3)Si moiety at the other end of a carbon chain, were prepared through the hydroboration of the corresponding unsaturated silanes. The C-centered radical species generated from these silylboranes efficiently cyclized to provide, through a 5-exo intramolecular homolytic substitution at the silicon center, the corresponding silacycle and a Me(3)Si radical that was subsequently trapped by sulfonyl acceptors. These cyclizations proceeded at unprecedented rates, due, in part, to a strong gem-dialkyl effect that was attributable to the presence of bulky substituents on a quaternary center located on the chain. In parallel, we designed arylsilylboranes that produced silyl radicals through a 1,5-hydrogen transfer. Such silyl radicals may be valuable radical chain carriers, for instance, in oximation reactions of alkyl halides. Finally, computational studies allowed calculation of activation barriers of the homolytic substitution step and additionally illustrated that the overall reaction mechanism involved a transition state in which the attacking carbon center, the central silicon atom, and the Me(3)Si leaving group were collinear.

Synthesis and analytical investigation of C‐terminally modified peptide aldehydes and ketone: application to oxime ligation

C-terminally modified peptides aldehyde (glycinal and alpha-oxo aldehyde peptides) and ketone (pyruvic acid-containing peptide) were synthesised to get new insights into the mechanism of acido-catalysed oxime ligation. Their tetrahedral hydrated forms were investigated in solution and in the gas phase, using NMR and in-source collision-induced dissociation mass spectrometry, respectively, and the kinetics of the oximation reactions followed using analytical HPLC. The results obtained confirmed that the first step of the oximation reaction was the limiting step for the pyruvic acid-containing peptides because of the steric effect and of the carbon angular strain of the ketone. The second step is the determining step for the aldehyde peptides because the basicity of the oxygen of the hydroxyl function of the tetrahedral form is greater for glycinal than for alpha-oxo aldehyde. These data strongly suggest that the hydrated form of the aldehyde partner has to be considered when oxime reactions are performed in aqueous buffer.

Development of Domino Reactions Based on Skeletal Rearrangement

Domino reactions, which enable formations of several chemical bonds and multi-step transformation in one-pot process, have received much attention as an efficient synthetic methodology to preserve chemists from time-consuming purification protocols and protection-deprotection procedures. Furthermore, the domino processes containing skeletal rearrangement have been utilized for constructions of complex molecules because of their potential that they could afford entirely different valuable structures from readily available simple substrates. We recently developed novel domino reactions including ring enlargement process, which could afford biologically important cyclopentanones and nitrogen heterocycles. In this review, we will describe 1) a novel type of palladium-catalyzed domino insertion-ring expansion reaction of dienylcyclobutanols, which could enable a stereospecific synthesis of (Z)-2-(3-aryl-1-propenyl)cyclopentanones, 2) ruthenium-catalyzed domino ring expansion-insertion reaction of 1-acetylenylcyclobutanols for a construction of 2-alkylidenecyclopentanones, and 3) DIBALH-mediated reductive ring expansion reaction of oximes and studies on the reaction mechanisms. The rationales for the observed stereoselectivities in each reaction are also discussed.

Implanting Nitrogen into Hydrocarbon Molecules through CH and CC Bond Cleavages: A Direct Approach to Tetrazoles

The development of novel methods for the preparation of tetrazoles is of long-standing interest and a challenge for organic chemists because of the importance of these compounds in chemistry and biology. In particular, 1,5-disubstituted tetrazoles are very useful compounds in medicinal chemistry and important synthetic intermediates. In the past several decades, some general strategies for the synthesis of 1,5-disubstituted tetrazoles from functionalized starting materials have been developed (Scheme 1). These methods include: a) the reactions of ketones or oximes with sodium azide and hydrogen azides, b) the reactions of amides with sodium azides in the presence of phosphorus(V) chloride or triflic anhydride and the reactions of amidrazones with dinitrogen tetroxide or nitrous acid, c) the reactions of imidoyl chlorides or imidoylbenzotriazoles with sodium azides and, d) the reactions of nitriles with alkyl azides. These developed methods significantly improved the synthesis of tetrazoles, but these approaches have some limitations, such as the use of protic acid catalysts, tedious workups, and the use of functionalized starting materials, hence encouraging scientists to discover new strategies. The direct transformation of hydrocarbon molecules by transition-metal-catalyzed selective C H and C C bond activation (cleavage) has attracted considerable attention, owing not only to its fundamental scientific appeal but also to its potential utility in organic synthesis. A direct approach to tetrazoles through C H and C C bond cleavages of simple hydrocarbon molecules is still an extremely attractive yet challenging goal. Herein, we demonstrate a novel and efficient Cu-promoted implanting of nitrogen into simple hydrocarbon molecules to construct 1, 5-disubstituted tetrazoles through C H and C C bond cleavages, and C N bond formation under mild and neutral reaction conditions (Scheme 1e). Azide has been widely used as a useful aminating reagent in organic synthesis. The application of azides for the direct synthesis of aryl nitriles and alkenyl nitriles through C H bond cleavage has been recently reported. Recent achievements on the functionalization of C H and C C bonds encouraged us to try the direct synthesis of

Expeditious preparation of isoxazoles from Δ2-isoxazolines as advanced intermediates for functional materials

A collection of isoxazoles derivatives has been efficiently synthesized in three steps. The oximation reaction of aldehydes followed by nitrile oxide [3+2] 1,3-dipolar cycloaddition and MnO2-oxidation reaction furnished the title compounds which were purified by simple filtration on celite®.

A Novel Reaction of α-Carbonyl Oxime and Amido Alcohol: Synthesis, Characterization, Crystal Structure, and Thermal Studies of an Amido Alcohol, a New Oximino Alcohol Ligand, and its Metal Complexes

In this study, a novel reaction was observed between isonitrosoacetophenone and 1-phenylethanol amine. Acetophenone was used as a starting material to synthesize isonitrosoacetophenone by reaction of acetophenone with n-butyl nitrite in the presence of sodium ethoxide and to synthesize 1-phenylethanol amine by reduction of isonitrosoacetophenone with LiAlH4 in diethyl ether. When the isonitrosoacetophenone reacted with 1-phenylethanol amine, (3E)-3-aza-5-(hydroxyimino)-1,4-diphenylpent-3-en-1-ol monohydrate, a new oximino alcohol ligand and amido alcohol were obtained as associated product interestingly. Four complexes were prepared by treatment of oximino alcohol with metal salts such as CuII, NiII, ZnII, and CoII. Amido alcohol was characterized by single-crystal x-ray diffraction, and all complexes were characterized by using spectroscopic techniques and thermogravimetric analysis (TGA).

Synthesis of Indenoporphyrins, Highly Modified Porphyrins with Reduced Diatropic Characteristics

Indene-fused porphyrins have been synthesized starting from 2-indanone. Knorr-type reaction of oximes derived from benzyl or tert-butyl acetoacetate with 2-indanone and zinc dust in propionic acid gave good yields of indenopyrroles. Treatment with N-chlorosuccinimide then gave 8-chloro derivatives, and these reacted with 5-unsubstituted pyrroles to give dipyrroles incorporating the fused indene unit. Hydrogenolysis of the benzyl ester protective groups afforded the related dicarboxylic acids, but condensation with a dipyrrylmethane dialdehyde under MacDonald "2 + 2" reaction conditions gave poor yields of the targeted indenoporphyrins. However, when an indene-fused dipyrrole was converted into the corresponding dialdehyde with TFA-trimethyl orthoformate and then reacted with a dipyrrylmethane dicarboxylic acid, an indenoporphyrin was isolated in 26% yield. The porphyrin gave a highly modified UV-vis absorption spectrum with three strong bands showing up in the Soret region and a series of Q bands that extended beyond 700 nm. The proton NMR spectrum also showed a significantly reduced diamagnetic ring current where the meso-protons gave resonances near 9.3 ppm instead of typical porphyrin values of 10 ppm. Nickel(II), copper(II), and zinc complexes were also prepared, and these exhibited unusual UV-vis absorption spectra with bathochromically shifted Soret and Q absorptions. The diamagnetic nickel(II) and zinc complexes also showed reduced diatropic character compared to typical nickel(II) and zinc porphyrins.

ChemInform Abstract: Gold‐Catalyzed Rearrangement of O‐Vinyl Oximes for the Synthesis of Highly Substituted Pyrroles.

AbstractO‐vinyl oximes, synthesized by reaction of oximes with alkynecarboxylates, undergo an unprecedented Au‐catalyzed rearrangement to yield pyrroles [e,g.

Dynamic Path Bifurcation in the Beckmann Reaction: Support from Kinetic Analyses

The reactions of oximes to amides, known as the Beckmann rearrangement, may undergo fragmentation to form carbocations + nitriles when the migrating groups have reasonable stability as cations. The reactions of oxime sulfonates of 1-substituted-phenyl-2-propanone derivatives (7-X) and related substrates (8-X, 9a-X) in aqueous CH(3)CN gave both rearrangement products (amides) and fragmentation products (alcohols), the ratio of which depends on the system; the reactions of 7-X gave amides predominantly, whereas 9a-X yielded alcohols as the major product. The logk-logk plots between the systems gave excellent linear correlations with slopes of near unity. The results support the occurrence of path bifurcation after the rate-determining TS of the Beckmann rearrangement/fragmentation reaction, which has previously been proposed on the basis of molecular dynamics simulations. It was concluded that path-bifurcation phenomenon could be more common than thought and that a reactivity-selectivity argument based on the traditional TS theory may not always be applicable even to a well-known textbook organic reaction.

Copper(II)-mediated oxime–nitrile coupling in non-aqueous solutions: Synthetic, structural and magnetic studies of the copper(II)–salicylaldehyde oxime reaction system

The reactions of salicylaldehyde oxime (H 2salox) with Cu II precursors yielded the known complexes [Cu(Hsalox) 2] ( 1) and [Cu(Hsalox) 2] n ( 2), as well as complexes [Cu 3(salox)(L 1)(L 2)]·MeCN ( 3·MeCN), [CuCl(L 1)] ( 4) and [Cu 2Na(O 2CMe) 5(HO 2CMe)] n ( 5), where L 1 − = o-O–C 6H 4–CH NO–C(CH 3) NH and L 2 3− = o-O–C 6H 4–CH NO–C( o-O–C 6H 4) N. L 1 − was formed in situ via the nucleophilic addition of the oximato O-atom of salox 2− to the unsaturated nitrile group of the MeCN reaction solvent. L 2 3− is also formed in situ probably through the nucleophilic attack of the oximato O-atom to the unsaturated nitrile group of salicylnitrile; the latter, although not directly added to the reaction mixture, can be produced via the dehydration of salox 2−. Compounds 1 and 2 contain Hsalox − bound to the metal center in two different coordination modes; they both contain the same mononuclear unit, however a 2D network is generated in 2 due to a relatively long Cu–O oximato bond. Compound 3 contains three different ligands, i.e. salox 2−, L 1 − and L 2 3−, which act as μ 3-κ 2 O:κ O′:κ N, κ O:κ N:κ N′ and μ 3-κ 2 O:κ 2 N:κ O′:κ N′, respectively, whereas 4 consists of a square planar Cu II atom bound to a κ O:κ N:κ N′ L 1 − and a chloride ion. Compound 5 consists of dinuclear [Cu 2(O 2CMe) 5(HO 2CMe)] − units and Na + ions assembled into an overall 3D network structure. Magnetic susceptibility measurements from polycrystalline samples of 2 and 5 gave best-fit parameters J = +0.36 cm −1 ( H = −J Ŝ i Ŝ j ) and J = −360 cm −1, zj = +20 cm −1 ( H = −J Ŝ i Ŝ j − zJ〈S z〉 Ŝ z ), respectively.

Gold-catalysed rearrangement of O-vinyl oximes for the synthesis of highly substituted pyrroles

O-Vinyl oximes were synthesised from the reaction of oximes with activated alkynes and subsequently rearranged using gold catalysis to afford highly substituted pyrroles in an efficient and regiocontrolled process. Additionally, pyrroles were formed directly from oximes and activated alkynes in a multifaceted catalysis process.

Supercritical Water Properties and Beckmann Rearrangement Reaction: First Principles Molecular Dynamics Study

Physical and chemical properties of supercritical water were investigated by first principles molecular dynamics (FPMD). Hydrogen bonds are present in supercritical water, but do not form a network, resulting in formation of various sizes of clusters. FPMD confirmed that Beckmann rearrangement reaction of cyclohexanone oxime to ε-caprolactam occurs via a hydronium ion in the supercritical water at 670 K and 0.7 g/cm3, not due to the high temperature but to the low density. The hydronium ion is not completely solvated by three water molecules because of the low density of the supercritical water, resulting in high reactivity. No Beckmann rearrangement reaction takes place even at 670 K and normal water density of 1 g/cm3, since the hydronium ion is stabilized by complete solvation.

A novel microreactor approach for analysis of ketones and aldehydes in breath

We report a fabricated microreactor with thousands of micropillars in channels. Each micropillar surface is chemically functionalized to selectively preconcentrate gaseous ketones and aldehydes of exhaled breath and to enhance ultra-trace, rapid analysis by direct-infusion Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometry (MS). The micropillar reactive coating contains the quaternary ammonium aminooxy salt 2-(aminooxy)ethyl-N,N,N-trimethylammonium iodide (ATM) for capturing trace carbonyl VOCs by means of an oximation reaction. We demonstrate the utility of this approach for detection of C(1) to C(12) aldehydes and ketones in exhaled breath, but the approach is applicable to any gaseous sample.

Novel Condensed Ring Carboxylic Hydroxamic Acid Studied in the Flotation Behavior of Diaspore and Aluminosilicates

Flotation reagents are the critical technique in the flotation separation process for desilication. Aimed at the highly selective reagent for direct flotation of diasporic bauxite, a novel compound, dibenzo-1-(7-carboxyl-4-hydroxyl bicycle [2.2.2] octan-7,8-diyl) carboxamic acid (DBCA) with two functional groups carboxyl and hydroxamate in the same molecule, was synthesized through Diels-Alder reaction followed by oximation reaction. Subsequently, the floatability of diaspore, kaolinite, and illite was measured by using DBCA as a collector, the interaction mechanism between minerals and DBCA was investigated through zeta potential measurements and FT-IR spectrum, and the structure and property relationship of the collector were also discussed. The flotation experimental results showed that DBCA had a very strong collecting ability for diaspore, while poor activity was observed for kaolinite and illite. The interaction of DBCA on diaspore surfaces may be mainly dominated by chemical bonding as the formation of three chelation rings; however, those on the surfaces of kaolinite and illite are mainly hydrogen bonding or physical adsorption. Consequently, it is possible to separate diaspore from such aluminosilicates as kaolinte and illite employing DBCA as a collector.

ChemInform Abstract: Chemoselective Protection of α‐Ketoacids by Direct Annulations with Oximes.

AbstractCyclic nitrones, generated in the reaction of oximes with α‐ketoacids, serve as stable masked α‐ketoacids.

ChemInform Abstract: Some Properties of Cyclopropenone Oximes Under Beckmann Reaction Conditions.

The reaction of diphenylcyclopropenone oxime (1a) with acetyl or tosyl isocyanate, carboxylic anhydrides, or nitrohalobenzenes yielded the cyclopropenone O-substituted oxime derivatives. Treating with thionyl bromide and chloride 1a gave 3-haloacrylonitriles. Whereas 1a as well as other cyclopropenone oximes, were stable under acidic conditions, heating in methanolic sodium hydroxide gave the ring-opened α,α-dimethoxyketones oximes.

ChemInform Abstract: Additional Reactions of Sugar Oximes, Nitrile Oxides and Hydroximolactones.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

In situ multinuclear solid-state NMR spectroscopy study of Beckmann rearrangement of cyclododecanone oxime in ionic liquids: The nature of catalytic sites

The Beckmann rearrangement of cyclododecanone oxime into ω-laurolactam has been investigated in four ionic liquids: 1-butyl-3-methylimidazolium hexafluorophosphate and tetrafluoroborate ( [ C 4 mim ] + PF 6 - , [ C 4 mim ] + BF 4 - ) , and 1-butyl-2,3-dimethylimidazolium and 1-butyl-4-methylpyridinium hexafluorophosphates ( [ C 4 mpyr ] + PF 6 - , [ C 4 m 2 im ] + PF 6 - ) , in a batch reactor as well as by ‘in situ’ multinuclear solid-state NMR spectroscopy. The Beckmann rearrangement reaction of cyclododecanone oxime takes place in [ C 4 mim ] + PF 6 - and [ C 4 mpyr ] + PF 6 - with excellent activity and selectivity, while practically null activity is observed in [ C 4 m 2 im ] + PF 6 - and [ C 4 mim ] + BF 4 - . The results obtained indicate that a very low level of hydrolysis of the PF 6 - anion in [ C 4 mim ] + PF 6 - and [ C 4 mpyr ] + PF 6 - occurs under reaction conditions (130 °C), and the HF formed at the level of ppm acts as catalyst in the Beckmann rearrangement with excellent conversion and selectivity.

ChemInform Abstract: 1,3,5‐Triphenylbenzene as Unexpected By‐Product in the Synthesis of 2,5‐Diphenylpyrrole from Acetophenone Oxime and Phenylacetylene.

Despite poor yield of the target product (25%), the reaction of acetophenone oxime (I) with phenylacetylene (II) in superbasic medium (Trofimov reaction) [1–4], leading to 2,5-diphenyl-1H-pyrrole (III), attracts interest from the preparative viewpoint, for alternative methods include a number of steps [5], and the overall yield (calculated with account taken of all steps) is comparable to that in the Trofimov synthesis. Determination of structure of by-products in the reaction of oxime I with acetylene II may be useful for understanding its mechanism and further optimization to enhance its preparative efficiency. We were the first to isolate from the product mixture (LiOH–DMSO, 130°C, 5 h) 6% of 1,3,5-triphenylbenzene (V) together with pyrrole III and acetophenone IV (deoximation product of initial oxime I) (Scheme 1). However, this assumption was not confirmed experimentally. We also found that under the given conditions compound V cannot be formed as a result of autocondensation of oxime I or ketone IV. Presumably, O-vinyl oxime VI which is the primary intermediate in the synthesis of pyrroles from ketone oximes and acetylene [6] (Scheme 2) undergoes rearrangement into nitrone VII (as reported in [7] for cyclohexanone oxime O-allyl ether). Enhanced CH acidity of the CH3 group in VII due to strong electron-withdrawing effect of the N-oxide fragment favors aldolization (crotonization) of VII with acetophenone IV. The condensation of azatriene VIII thus formed with the second acetophenone molecule gives azatetraene IX, and cyclization of the latter, followed by aromatization of dihydrobenzene X via elimination of vinylnitrone XI, yields triphenylbenzene V. Compound XI can be converted into acetophenone oxime (I).