<Superscript>13</Superscript>C-<Superscript>13</Superscript>C spin-spin coupling constants in structural studies: XLIV. Carbonyl-containing oximes

¹³C-¹³C spin-spin coupling constants in carbonyl-containing oximes were calculated in terms of the second-order polarization propagator approximation (SOPPA) with account taken of the results of theoretical conformational analysis. Stable conformations of all carbonyl-containing oximes were found to have s-trans orientation of the carbonyl group in the E and Z isomers. The corresponding ¹³C-¹³C coupling constants showed a characteristic dependence upon internal rotation of the carbonyl-containing substituent, which may be used to determine predominant rotational conformations of these compounds. A relation between orientation of the C=O bond and ¹³C-¹³C coupling constants for the adjacent bonds in oximes was revealed; it may be attributed to hyperconjugation between the corresponding carbon-carbon bond and antibonding orbital of the C=O bond.     

Nucleophilic addition of aromatic amide oximes to [2-B<Subscript>10</Subscript>H<Subscript>9</Subscript>NCC<Subscript>2</Subscript>H<Subscript>5</Subscript>]<Superscript>–</Superscript> anion

A series of closo-decaborate anions containing an O-iminoacylamide oxime fragment were synthesized by nucleophilic addition of aromatic amide oximes to 2-propionitrilium closo-decaborate anion. The isolated compounds were characterized by IR, ¹H, ¹³C–{¹H}, and ¹¹B–{¹H} NMR, and mass spectra. The structure of (Ph₄P)[2-B₁₀H₉NH=C(Et)ON=C(NH₂)C₆H₄Me-2] was determined by single-crystal X-ray analysis.     

The fragmentation of ortho-methoxyphenyl-2-propanone oximes and related compounds–further examples of an ortho-effect

An [M ? 31]⁺ ion was a prominent fragment in the mass spectra of three ortho-methoxy-phenyl-2-propanone oximes and is shown to be due to the expulsion of a methoxyl radical from the molecular ion as a result of an ortho-effect. In contrast, an [M ? 31]⁺ ion was absent from the spectra of a structurally related ketone and a hydroxylamine, and was not observed in the spectra of meta- and para-methoxyphenyl-2-propanone oximes.     

1H and 13C NMR spectra of N-vinylpyrroles

The position of the substituants in 2, 3-dialkyl-1-vinylpyrroles and 7-methyl-1 vinyl-4,5,6,7-tetrahydroindole was established on the basis of the ¹H and ¹³C NMR spectra. It was found that the S-trans conformation of the N-vinyl group is preferred. It is shown that the condensation of ketoximes with acetylene proceeds through the formation of free pyrroles and that vinyl oximes are not intermediates in the condensation.     

Electron impact and chemical ionization mass spectra of 2,2-diphenyl-3-arylcyclobutanone oximes. Formation of ion m/z 167

The electron impact (EI) and chemical ionization (CI) spectra of 2,2-diphenyl-3-aryl cyclobutanone oximes (1–5) are reported. Formation of diphenylmethyl cation at m/z 167 is a major fragmentation process in both EI and CI spectra. Labelling studies established that the hydrogen involved in this rearrangement transfers from the NOH group and not from cyclobutane ring positions. The [M + 3]⁺ ions are formed under CI conditions as a result of C?N double bond reduction. An interesting secondary kinetic isotope effect is observed in the formation of ion e at m/z 183 in both EI and CI spectra. Other characteristic fragmentation pathways occurring in the EI and CI spectra of these compounds are outlined.     

Comparative analysis of 13C shielding constants stereospecificity in the silicon and germanium derivatives of acetylenic aldehyde and ketone oximes based on the 13C NMR spectroscopy and GIAO calculations

In the acetylenic aldehyde oximes with substituents containing silicon and germanium, the ¹³C NMR signal of the C‐2 carbon of triple bond is shifted by 3.5 ppm to lower frequency and that of the C‐3 carbon is moved by 7 ppm to higher frequency on going from E to Z isomer. A greater low‐frequency effect of 5.5 ppm on the C‐2 carbon signal and a greater high‐frequency effect of 11 ppm on the C‐3 carbon signal are observed in the analogous acetylenic ketone oximes. The carbon chemical shift of the C?N bond is larger by 4 ppm in E isomer relative to Z isomer for the aldehyde and ketone oximes. The ²⁹Si chemical shifts in the silicon containing acetylenic aldehyde and ketone oximes are almost the same for the diverse isomers. The trends in changes of the measured chemical shifts are well reproduced by the gauge‐including atomic orbital (GIAO) calculations of the ¹³C and ²⁹Si shielding constants. Copyright © 2009 John Wiley & Sons, Ltd.     

DFT and experimental determination of conformations of 2‐(ethoxycarbonylmethoxy)‐5‐(arylazo)benzaldehydes and their oximes

2‐(Ethoxycarbonylmethoxy)‐5‐(arylazo)benzaldehydes 1–4 and their oximes 5–8 were synthesized and characterized by IR, ¹H and ¹³C NMR spectroscopy. The favoured conformations of aldehydes 1–4 and oximes 5–8 were predicted theoretically. Selected geometrical parameters and charges were derived from optimized structures. IR, ¹H and ¹³C NMR data were also computed using Gaussian‐03 package and compared with the observed values. ¹⁵N and ¹⁷O chemical shifts were also determined theoretically. Copyright © 2012 John Wiley & Sons, Ltd.     

Characteristic frequencies in the infrared spectra of pyrazolines

Pyrazolines are characterized by valence vibrations at the following frequencies: C=N (1580–1627 cm^–1), H-C³=N (3040–3063 cm^–1), H-N (3270–3305 cm^–1) and CH₃-N (2780–2805 cm^–1). Lowering of the frequencies of the valence vibrations of C=N in pyrazolines, when compared with the magnitudes characteristic of alkyledene amines and oximes, is regarded as a consequence of coupling with the unshared electron pair of the neighboring nitrogen atom. By means of the IR spectra, it is possible to determine the position of the double bonds in the pyrazoline ring, to distinguish between pyrazolines substituted and nonsubstituted in positions 1 and 3, and to establish the presence of geminate (twin) methyl groups and methyl groups in position 1.     

One step from nitro to oxime: a convenient preparation of unsaturated oximes by the reduction of the corresponding vinylnitro compounds

A series of novel unsaturated oximes were conveniently prepared from the corresponding vinylnitro compounds by reduction with SnCl₂·2H₂O. The structures of the oximes were characterized by ¹H and ¹³C NMR, IR and HRMS, and X-ray crystallography analysis of 1-(6-chloro-pyridin-3-ylmethyl)-4,5-dihydro-1H-imidazole-2-carbaldehyde oxime 2a reveals that, the hydroxyl group is arranged in a trans configuration. Some evidences from a brief investigation suggest that these oximes seem to be formed by reduction of the aci form of nitro aliphatic compounds.     

Synthesis of α-amino oximes and bis-α-amino oximes from the monoterpene hydrocarbons 3-carene and α-pinene and α,ω-diamines

The reaction of nitroso chlorides of natural monoterpene hydrocarbons, 3-carene and -pinene, with simple ,-diamines (1,2-diaminoethane, 1,3-diaminopropane, piperazine, 1,6-diaminohexane, diethylenetriamine) results in the formation of -amino oximes and bis--amino oximes. The product structures were proved by spectroscopy. The procedures of separation and purification of diamino oximes and diamino dioximes are described. Detailed analysis of the ¹H and ¹³C NMR spectra of the new chiral nitrogen-containing derivatives was carried out.     

Reactions of 2-aryl (hetaryl) methylene-3-oxoquinuclidines with bifunctional nucleophilic reagents

The reactions of 2-aryl(hetaryl)methylene-3-oxoquinuclidines with hydrazine hydrate, thiourea, and phenylhydrazine gave, respectively, 7-phenyl-7,7a,dihydropyrazolo[3,4-b]quinuclidine, 7-(4-methoxyphenyl)-7,7a-dihydropyrazolo[3,4-b]quinuclidine, 7-(2-thienyl)-7,7a-dihydropyrazolo-[3,4-b]quinuclidine, 3,3-azinobis (2-benzylidenequinuclidine), 3,3-azinobis[2-(4-methoxybenzylidene)quinuclidine], 6-thio-8-phenyl-5,6,7,8-tetrahydropyrimido[5,4-b]quinuclidine, 2-benzylidene -3-oxoquinuclidine phenylhydrazone, and 2-(4-methoxybenzylidene)-3-oxoquinuclidine phenylhydrazone. The structures of the compounds were confirmed by the IR and ¹H and ¹³C NMR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 793–797, June, 1982.     

Study of three-dimensional structures of benzoylpyridine oximes and their ethers by 1H and 13C NMR spectroscopy

The ¹H and ¹³C NMR spectra of the E and Z isomers of 2-, 3-, and 4-benzoylpyridine oximes and their ethers were analyzed thoroughly, and the ¹H-¹³C spin-spin coupling constants (SSCC) were determined. It was established that the magnitude of the effect for the quaternary carbon atoms in the E and Z isomers depends on the site of substitution in the pyridine ring. It was assumed that the intermolecular hydrogen bond is stronger in the E form than in the Z form. The existence of the Z isomer of 2-benzoylpyridine oxime in deuterochloroform with an intramolecular hydrogen bond was proved.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 203–208, February, 1990.     

Stereospecificity of shielding constants of carbon-13 nuclei in 13C NMR spectra of oximes of hetarenecarbaldehydes and alkyl heteryl ketones

It has been discovered that the chemical shifts of carbon atoms in ¹³C NMR spectra of oximes having pyrrolyl, furyl, benzofuryl, thienyl, and pyridyl rings as substituents are changed systematically on going from the E- to the Z-isomer. This makes it possible to use the indicated chemical shifts for establishing the configuration of oximes with heterocyclic substituents and studying the special features of their electronic structure. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1523–1531, October, 2008.     

Selective conversion of C=N bonds to their corresponding carbonyl compounds by the tribromoisocyanuric acid/wet SiO2 system as a novel reagent

Abstract  

Tribromoisocyanuric acid/wet SiO₂ was used for the conversion of C=N bonds to their corresponding carbonyl compounds in oximes, semicarbazones, azines, and Schiff bases. The interesting feature of this system is that in those oximes, semicarbazones, azines, and Schiff bases which have conjugated or unconjugated C=C bonds, the C=N bond will selectively change to the relevant C=O bond while the conjugated or unconjugated C=C bond will remain intact.     

Mass Spectra of Furfuryl Aldoximes and Ketoximes

The mass spectra of 8 furfuryl aldoximes and ketoximes were studied under EI and CI conditions. Complicated fragmentation patterns were obtained in EI conditions, including formation of a furfuryl cation radical, furfuryl cation, and [M-17]⁺. The relatively simple patterns of cleavage resulted in few major ion peaks contributed from the adducts, protonation products, and dehydration products under CH₄-CI and NH₃-CI conditions. Comparison with the spectra of their isomeric amides indicated no evidence that the isomerization took place from oximes before fragmentation in both ionization methods.     

Axial ligation of imidazole to cobalt(III) oximes

Summary Non-homoleptic, octahedral cobalt(III) complexes are formed by the aerial oxidation of cobalt(II) salts in the presence of either (anti)-furfuraldoxime (HL¹) or salicylaldoxime (HL²) and imidazole. The analytical data, electrical conductance, electronic, vibrational and n.m.r. (¹H and¹³C) spectra as well as magnetic susceptibility and thermal decomposition measurements have been employed to deduce the stoichiometry and stereochemistry of the complexes. The oximes are bonded as bidentate chelates occupying the planar positions and the complexes havetrans-octahedral geometry with the imidazole and an anion in the axial positions. The thermogravimetric analysis of the complexes indicate their thermal stability at ambient temperatures, and with the increase in temperature they lose the ligands in discrete steps forming polymeric intermediates, and Co₃O₄ as the ultimate end product above 500°C.     

<Superscript>1</Superscript>H and <Superscript>31</Superscript>P nuclear spin-lattice relaxation in C-phosphorylated oximes

The ¹H spin-lattice relaxation times of the proton-bearing groups and the ³¹P spin-lattice relaxation times in C-phosphorylated oximes R¹C(=NOH)P(=O)R²R³ (R¹ = Ph, R² = R³ = OMe; R¹ = Ph, R² = OMe, R³ = OCH²CH²Br; R¹ = PhCH², R² = R³ = OCHMe²) and dioxime R²P(=O)C(=NOH)(CH₂)₄C(=NOH)P(=O)R² (R = OMe) in DMSO-d₆ were measured. The characteristic reorientation times of the whole molecules were estimated using the measured values of the ¹H relaxation times and the results of semiempirical PM3 quantum chemical calculations of the molecular geometries. The reorientation times were used to identify the contributions of different relaxation mechanisms to the rate of ³¹P spin-lattice relaxation. The anisotropy of the chemical shielding of ³¹P nuclei was evaluated from the difference between the ³¹P relaxation rates measured at 101.27 and 161.92 MHz.     

Monomere Tetramethylarsen- und Antimon-Verbindungen mit fünffacher Koordination am Zentralatom

Monomeric Tetramethylarsenic and Antimony Compounds with Coordination Number Five at the Central Atom The pentaalkyl compounds (CH₃)₅As and (CH₃)₅Sb react with aequimolar amounts of alcohols, hydroxylamines, and oximes to produce methane and the compounds (CH₃)₄MX (with X = ? OR, ? ONH₂, ? ONR₂, ? ON?CR₂ and M?As, Sb). According to vibrational spectra and low temperature ¹H-n.m.r. spectra the monomeric compounds posses a trigonal bipyramidal structure.     

C（sp3）-H bond functionalization of oximes derivatives via 1,5-hydrogen atom transfer induced by iminyl radical

Oximes derivatives have been vastly used in organic synthesis. In this review, C（sp³）-H bond functionalization of oximes derivatives via iminyl radical induced 1,5-hydrogen atom transfer was discussed. According to the different type of products, this review was divided into three parts:（1） C（sp³）-H bond functionalization for C-C bond formation.（2） C（sp³）-H bond functionalization for C-N bond formation.（3） C（sp³）-H bond functionalization for C-S, C-F b...     

Steroids and Sex Hormons. Part 263. [1]. On the Mechanism of the Reaction of 17-Hydroxyimino-steroids with Carbodiimide/Dimethylsulfoxide

Treatment of the (Z)-isomers 6 and 7 of the four isomeric 16-acetoxy-17-hydroxyimino-steroids 6–9 with DCC/DMSO/CF₃COOH (Moffat fragmentation of oximes) yielded the seco-α-acetoxy-nitriles 10 and 11 , respectively, while similar treatment of both (E)-isomers 8 and 9 gave the formyl-carbonitrile 14. The mechanism of these fragmentations is discussed. ¹³C-NMR. data of oximes are presented which show the γ-gauche effect being associated with σ (C? H)-bond polarization.