Formation of Zinc(II) and Cadmium(II) Complexes with Pyridine Oxime Ligands in Aqueous Solution

Complex formation equilibria involving pyridine-2-carboxaldehyde oxime (1), 1-(2-pyridinyl)ethanone oxime (2) and 6-methylpyridine-2-carboxaldehyde oxime (3), HL, with zinc(II) and cadmium(II) ions were studied in aqueous 0.1 M NaCl solution at 25° C by potentiometric titrations with a glass electrode. Experimental data were analysed with the least-squares computer program SUPERQUAD to determine the complexes formed and their stability constants. With Ligands 1 and 2 the sets of complexes for Zn(II) and Cd(II) are essentially the same, mono- and dinuclear oxime complexes and their deprotonated/hydrolysed products H_pM_q(HL)^2q+p _r. Owing to the steric requirements of the 6-methyl group, sets of complexes formed with 3 are distinctly different. For zinc(II), only dinuclear oximato species H_pZn₂(HL)^4q+p ₂ ( p = ? 2, ? 3, ? 4) are found, while for the larger cadmium(II) ion mononuclear oximato species CdL⁺ and CdL₂ are detected in addition to the dinuclear complex H_pCd₂(HL)^4q+p ₂ ( p = ? 3).     

Oxydation vanadique de l'hydroxy-8-quinoleine,la methyl-2-hydroxy-8-quinoleine et l'amino-8-quinoleine : Applications Analytiques

(Oxidation of 8-quinolinol, 2-methyl-8-quinolinol and 8-quinolinamine with vanadium(V). Analytical applications.)The study of the oxidation by vanadium(V) in 5 M sulphuric acid of these quinoline derivatives demonstrates the essential part played by substitution at the 8-position. At room temperature with a reaction time of 15 min, 4–40 μmol (optimally 20–35 μmol) of the compounds can be determined, with a vanadium (V) consumption of 19–20 mol mol^?1, by back-titration with iron(II) solution to a potentiometric end-point; relative standard deviations are <3%. At higher temperatures, the oxidation involves opening of the homocycle of the quinoline molecule with formation 2-pyridone-3-carboxylic acids. The products are characterized by elemental analysis, and infrared, n.m.r. and mass spectrometries.     

A study of the electron impact induced retro-diels-alder process with selected 5,6,6a, 7,12,12a-hexahydrobenzo[a]anthracenes

The mass spectra of 5,6,6a,7,12,12a-hexahydrobenzo[a]anthracene and 2-methoxy, 3-methoxy-, 4-methoxy and 1-methyl-4-methoxy derivatives are reported. Among the fragment ions observed under electron impact ionization, [C₈H₈]^+· and [M? C₈H₈]^+· can be generated by a retro-Diels-Alder process. Studies of metastable ion reactions show these ions to be formed by fragmentation directly from the molecular ion. The CA spectra of the [C₈H₈]^+· ions from the subject compounds were compared with spectra from ions of the same composition from various sources. From these data, kinetic energy release measurements and stereochemical considerations, it is concluded that these ions are formed by a stepwise, rather than a concerted mechanism.     

Redistribution reactions in the ion source of a mass spectrometer of complexes of titanium (iv), tin (iv) and germanium (iv) with 8-quinolinolato and halo or ethoxy ligands

The relative intensities of peaks in the mass spectra of the compounds MX_4?nox_n (oxH = 8-quinolinol; n = 2; M = Ti; X = F, Cl, Br or OEt; M = Sn; X = F, Cl, Br or I; M = Ge; X = Cl or Br; n = 1; M = Ti; X = OEt) depend on the insertion temperature and the residence time of the sample in the mass spectrometer. In most cases ions which cannot arise by fragmentation of the respective molecular ions are observed. These ions arise from the ionisation and fragmentation of species which are due to redistribution reactions in the mass spectrometer. The fragmentation pattern of the compounds MX₂ox₂ (X = halogen), mainly involving loss of ligand radicals, is related to the common oxidation states of the metals and reflects the metal-halogen bond strength. The molecular ions of the compounds Ti(OEt)_4?nox_n (n = 0, 1 or 2) fragment by loss of intact ligand radicals.     

Cloud point extraction of iron(III) and vanadium(V) using 8-quinolinol derivatives and Triton X-100 and determination of 10(-7)moldm(-3) level iron(III) in riverine water reference by a graphite furnace atomic absorption spectroscopy

The cloud point extraction behavior of iron(III) and vanadium(V) using 8-quinolinol derivatives (HA) such as 8-quinolinol (HQ), 2-methyl-8-quinolinol (HMQ), 5-butyloxymethyl-8-quinolinol (HO₄Q), 5-hexyloxymethyl-8-quinolinol (HO₆Q), and 2-methyl-5-octyloxymethyl-8-quinolinol (HMO₈Q) and Triton X-100 solution was investigated. Iron(III) was extracted with HA and 4% (v/v) Triton X-100 in the pH range of 1.70-5.44. Above pH 4.0, more than 95% of iron(III) was extracted with HQ, HMQ, and HMO₈Q. Vanadium(V) was also extracted with HA and 4% (v/v) Triton X-100 in the pH range of 2.07-5.00, and the extractability increased in the following order of HMQ < HQ < HO₄Q < HO₆Q. The cloud point extraction was applied to the determination of iron(III) in the riverine water reference by a graphite furnace atomic absorption spectroscopy. When 1.25 × 10⁻³ M HMQ and 1% (v/v) Triton X-100 were used, the found values showed a good agreement with the certified ones within the 2% of the R.S.D. Moreover, the effect of an alkyl group on the solubility of 5-alkyloxymethyl-8-quinolinol and 2-methyl-5-alkyloxymethyl-8-quinolinol in 4% (v/v) Triton X-100 at 25 °C was also investigated.     

Mass spectra of some 1-substituted-4-acetoacetyl-3-methylpyrazol-5-ols

The fragmentation of 1-phenyl-, l-(2′-pyridyl)- and 1-(4′-methyl-2′-quinolyl)-4-acetoacetyI-3-methyIpyrazol-5-ols (compounds 1, 2 and 3, respectively) on electron impact has been studied and the major processes interpreted. The common feature in the mass spectra of these compounds is the loss of ketene, acetonyl radical, acetone and two molecules of ketene from the molecular ion. Whereas the ion generated after the last process, which corresponds to 1-substituted-3-methyIpyrazol-5-ols, loses methyl cyanide in the case of 1, similar ions in the case of 2 and 3 lose ?₂HO moiety, necessitating an intramolecular hydrogen transfer followed by ring fission and subsequent loss of methyl cyanide. All these and other related processes have been substantiated with the help of accurate mass measurements of the fragment ions and B/E linked-scan spectra.     

Mixed-ligand complexes of osmium(III/IV)8-quinolinolates with one ketoximate ligand

Summary A group of mixed-tris chelates of type [OsAQ₂] [A = isonitrosoacetophenonate (A¹) and isonitroso-propiophenonate (A²); Q = deprotonated 8-quinolinol (Q¹) and 2-methyl-8-quinolinol (Q²)] have been prepared by two distinct synthetic approaches. [OsAQ₂]⁺, obtained by Ce^IV oxidation of [OsAQ₂], can be regenerated by hydrazine hydrate reduction of the former. The complexes, characterized by physico-chemical, magnetic and spectroscopic methods, exhibit several spin-allowed and spin-forbidden charge transfer transitions in their electronic spectra. In MeCN solution the OsN₃O₃ unit displays a nearly-reversible Os^IV-Os^III change and an Os^III-Os^II couple in the ca. -1.0– + 0.3V range versus s.c.e. The stability of the metal oxidation levels is discussed in terms of the chemical and electrochemical results.     

Synthesis of 2,10-diphenyl-2H-pyridazino[4,5-b]quinolin-1-one and 2,3-dihydro-9-phenyl-2-phenylamino-1H-pyrrolo[3,4-b]quinolin-1-one derivatives as peripheral-type benzodiazepine receptor ligands

The reaction of 2-chloromethyl-3-ethoxycarbonyl-4-phenylquinoline with phenylhydrazine, afforded 2,3-dihydro-9-phenyl-2-phenylamino-1H-pyrrolo[3,4-b]quinolin-1-one derivatives 2 along with a major amount of 3-ethoxycarbonyl-4-phenylquinoline-2-carboxaldehyde phenylhydrazone 4a . The geometric isomers of phenylhydrazone 4a , displaying solvent-dependent E-Z isomerism, were isolated, characterized by ¹H-nmr and mass spectra, and the Z-form easily cyclized to pyridazino[4,5-b]quinoline derivative 5a . Analogously, compounds 2b, 2c, 4b , 4c, 5b and 5c were obtained. The title compounds were tested as potential ligands for central and peripheral-type of benzodiazepine receptors, and the results are reported.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-containing drimane sesquiterpenoids from 11-dihomodriman-8α-ol-12-one

Beckmann reaction products of 11-dihomodriman-8α-ol-12-one oxime with Ac₂O in pyridine, 86% H₃PO₄, p-TsCl in pyridine, and PCl₅ in ether were investigated. It has been found that the major product from treatment of the oxime with Ac₂O is the oxime acetate. Reaction of the oxime with 86% H₃PO₄ gave (1S,2S,4aS,8aS)-2,5,5,8a-tetramethyldecahydro-1H-naphtho[1, 2][5, 6]-3-methyl-4,5-dihydro[1, 2, 6]oxazine; with p-TsCl, (1S,2S,4aS,8aS)-2,5,5,8a-tetramethyldecahydro-1H-naphtho[1, 2][5, 6]-2-methyl-4,5dihydro[1, 3, 6]oxazine; with PCl₅, a mixture of products containing 11-acetylamino- and 11-methylaminooxodrimenes that were isomeric at the double bond, norambreinolide, and a 1,3,6-oxazine.     

Reversible cyclomerization and long range hydrogen abstraction by electron impact of 7-coumarinyl diesters ROOC(CH2)nCOOR

The mass spectra of 4-methyl-7-coumarinyl and 7-coumarinyl diestes ROOC(CH₂)_nCOOR (n = 2-12) have ben studied by appearance potential measurements, deuterium labelling and by comparison with suitable reference compounds such as the mised diestes ROOC(CH₂)_nCOOR′ (R=4-methyl-7-coumarinyl and R′ = methyl and phenyl) and 3.4-dihydro-4-methyl-coumarinyl diestes. Observations on the fragment ions of m/e 324, produced from the 7-coumrinyl diestes and their photocyclomers, by elimination of the central bridge as O?C?CH? (CH₂)_n–2? CH?C?O, demonstrate the existence and reversible formation of cyclomeric molecular ions. A stable bound system between the coumrin end groups is formed only at high internal energies by expulsion of a hydrogen atom, followed by elimination of the central bridge from the [M? H]⁺ ion. It is also shown that the lifetime of the open form molecular ions decreases remarkably for chain lengths with n larger than 6.     

Study of two diastereomeric pairs of regiosomeric 2-isoxazolines by tandem mass spectrometry with electron impact ionization

On electron impact (EI) ionization, two cis/trans pairs of 4-methyl-5-phenyl and 4-phenyl-5-methyl regioisomeric 3-carbethoxy-2-isoxazolines showed normal mass spectra and mass-analysed ion kinetic energy (MIKE) spectra of metastable (MI) and collision-activated (CA) molecule ions, allowing unequivocal differentiation of the regioisomers. The cis/trans stereoisomers of each regioisomer showed very similar normal mass spectra. Very interestingly, the cis- and trans-4-phenyl-5-methyl stereoisomers appeared reasonably differentiated by the molecule ion MIKE spectra, whereas the 4-methyl-5-phenyl regioisomeric pair of stereoisomers did not. The influence of the phenyl substituent to the fragmentation processes was notable. Some fragments of interest were studied by comparison of their MIKE spectra with those of model ions, generated by EI from suitable substrates, including (i) the isomeric α,β-unsaturated oxime, namely ethyl (Z)-2-(hydroxymino)-3-methyl-4-phenylbut-3-enoate, a by-product of importance for the mechanism(s) of the addition/cycloaddition reactions of nitrile oxides to alkenes and (ii) trans-β-methylstyrene, a dipolarophilic reactant in the same reactions. The favoured heterocyclic C(5)–O(1) bond cleavage occurred only for the ionized 4-methyl-5-phenyl 2-isoxazoline pair, leading to a distonic ion of relevance, as it can represent either a reasonable precursor for both the isomerization to the ionized α,β-unsaturated oxime and the EI-induced cycloreversion yielding ionized β-methylstyrene, or the ionized form of a zwitterionic intermediate, which had been proposed previously for the addition/cycloaddition mechanism(s) in the solution phase, currently under study.     

Positive and negative ion mass spectra of Aryl-ONN-azoxy compounds containing electron withdrawing groups

The positive and negative ion mass spectra, at 70 eV, of p-RC₆H₄N(O)?NCOOCH₃ (R?H, Cl, Br, NO₂), C₆H₅N(O)?NCOOC₂H₅, p-RC₆H₄N(O)?NCONH₂ (R?H, Cl, Br, NO₂) and p-RC₆H₄N(O)?NCOC₆H₅ (R?H, Cl, Br, NO₂) are reported. The azoxyester derivatives show abundant molecular ions and a number of weak fragment and rearrangement ions in the positive ion mass spectra, whereas weak molecular ions and abundant low mass fragment ions are present in the negative ion mass spectra. Similar behaviour is observed in the mass spectra of the azoxyamides. Conversely, for the azoxycarbonyl compounds the positive molecular ion is absent. A ready cleavage of the N? CO bond occurs and only few fragments of low diagnostic value are formed, whereas the negative molecular ion is the base peak for all these compounds with the exception of the p-NO₂ derivative, where [M? O]^?? is the base peak and [M]^?? is the second major ion. The behaviour under electron impact of these classes of compounds is compared with that of azoxycyanides reported previously.     

Synthesis and Structural Studies of 2-(hydroxyimino)-1-methylpropylideneamino-phenyliminobutan-2-one Oxime, Ligand and its Complexes with Cu(II) and Ni(II)

A new ligand incorporating a dioxime moiety, (2E,3E)-3-[(2-{[(1E,2E)-2-(hydroxyimino)-1-methylpropylidene]amino}phenyl)imino]butan-2-one oxime, (H₂Phmdo) (3) has been prepared by reacting 2,3-butanedionemono-{O-[4-(1-methyl-2-oxo-propylideneaminooxy)-2,3-bis-(1-methyl-2-oxo-propylideneaminooxy-methyl)-but-2-enyl]-oxime} (2) with 1,2-phenylenediamine. Mono-, di- and trinuclear copper(II) and/or nickel(II) complexes of H₂Phmdo were characterized by elemental analyses, magnetic moments, ¹H-n.m.r. and ¹³C-n.m.r., i.r. and mass spectral studies. The mononuclear copper(II) and nickel(II) complexes of H₂Phmdo were found to have a 1:1 metal:ligand ratio. Elemental analyses, stoichiometric and spectroscopic data of the metal complexes indicated that the metal ions are coordinated to the oxime and imine nitrogen atoms (C=N). In the dinuclear complexes, in which the first Cu^(II) or Ni^(II) ion was complexed with nitrogen atoms of the oxime and imine groups, the second Cu^(II) ion is ligated with dianionic oxygen atoms of the oxime groups and are linked to the 1,10-phenanthroline nitrogen atoms. The data support the proposed structure of H₂Phmdo and its complexes.     

Stereochemical applications of mass spectrometry. 3—Energy dependence of the fragmentation of stereoisomeric methylcyclohexanols

Breakdown graphs have been constructed from charge exchange data for the epimeric 2-methyl-, 3-methyl- and 4-methyl-cyclohexanols. Although the breakdown graphs for epimeric pairs are essentially identical above ～12 eV recombination energy, significant differences are observed for the epimeric 2-methyl- and 4-methyl-cyclohexanols at low internal energies. For the 2-methylcyclohexanols the ratio ([M? H₂O]^+·/[M]^+·)_cis/([M? H₂O]^+·/[M]^+·)_trans is 3.2 in the [C₆F₆]^+· charge exchange mass spectra. This is attributed to both energetic and conformational effects which favour the stereospecific cis-1,4-H₂O elimination for the cis epimer. The breakdown graph for trans-4-methylcyclohexanol shows a sharp peak in the abundance of the [M? H₂O]^+· ion at ～10 eV recombination energy which is absent from the breakdown graph for the cis epimer. This peak is attributed to the stereospecific cis-1,4-elimination of water from the molecular ion of the trans isomer; the reaction appears to have a low critical energy but a very unfavourable frequency factor, and alternative modes of water loss common to both epimers are observed at higher energies. As a result, in the [C₆F₆]^+· charge exchange mass spectra the ([M? H₂O]^+·/[M]^+·)_trans/([M? H₂O]^+·/[M]^+·)_cis ratio is ～24, compared to the value of 13 observed in the 70 eV EI mass spectra. No differences are observed in either the metastable ion abundances or the associated kinetic energy releases for epimeric molecules.     

A convenient synthesis of 2-amino-4H-1,3,4-oxadiazino[5,6-b]-quinoxaline derivatives

The reaction of 6-chloro-2-(1-methylhydrazino)quinoxaline 4-oxide 5 with a 2-fold molar amount of ethyl chloroglyoxalate gave ethyl 8-chloro-4-methyl-4H-1,3,4-oxadiazino[5,6-b]quinoxaline-2-carboxylate 6 , whose reaction with hydrazine hydrate afforded the C₂-hydrazinocarbonyl derivative 7 . The reaction of compound 7 with nitrous acid provided the C₂-acylazide derivative 8 , which was converted into the C₂-amino 9 , C₂-carbamate 11a-c, 12a,b , and C₂-ureido 13a-c, 14 derivatives. The mass spectral fragmentation patterns were examined for compounds 10–14 , wherein the molecular ion peak did not appear in the mass spectra of compounds 10c, 11a-c, 12a,b, 13c , and 14.     

Bestimmung des Oxydationszustandes in Vanadiumkomplexen mit Hilfe von V—K-Röntgenabsorptionsspektren

Determination of the Oxydation State in Vanadium Complexes using V—K-Absorption Spectra The compounds resulting from the reaction of oxovanadium(IV) sulfate with 8-quinolinols in air were characterized by magnetic moments and V—K-absorption spectra. 8-quinolinol and its Mannich derivates (“CMAB-oxine”, “CMAP-oxine”) form vanadium(V) complexes. The oxovanadium(IV) compound of 7-methyl-8-quinolinol initially formed is not very stable in solution and tends to oxydation. Only the oxovanadium(IV) complex of 2-methyl-8-quinolinol has a good stability corresponding to that of β-diketone compounds.     

Elimination of carbon monoxide by electron impact on quinoline N-oxide,carbostyril and 8-hydroxyquinoline

Under electron impact, the molecular ions of quinoline N-oxide, carbostyril and 8-hydroxyquinoline lose carbon monoxide giving a fragment ion C₈H₇N (m/z 117), which was shown by collision-activated dissociation in each case to have the structure of the molecular ion of indole. Its formation from 8-hydroxyquinoline requires an unusual rearrangement. Isoquinoline N-oxide loses HCN rather than CO and gives a fragment which has the structure of the molecular ion of benzofuran. When the first three compounds were subjected to flash vacuum pyrolysis, quinoline N-oxide at 500–700°C gave carbostyril and indole was detected by gas chromatography/mass Spectrometry. At 900°C carbostyril and 8-hydroxyquinoline both gave indole in small amounts, detected by gas chromatography/mass Spectrometry.     

Ring contractions of dihydro- and tetrahydro-1,5-benzodiazepines in electron ionization mass spectrometry

Electron ionization mass spectra of a series of 2,4-disubstituted dihydro- and tetrahydro-1,5-benzodiazepines are discussed. The fragmentation of these compounds is dominated by ring contractions of diazepine, which give both five- and six-membered rings, benzimidazoles and quinoxalines. Tetrahydro compounds showed a tendency to eliminate one nitrogen from the ring system and give quinoline rings through NH₂ and NH₄ eliminations. The electron ionization spectra of cis and trans isomers of tetrahydro compounds are identical.     

Redox troponization as a novel method for the synthesis of stereoisomeric Eschenmoser's oximes and related non-benzenoid aromatic systems

A novel method for the synthesis of the oxime of 4-methyl-2,4,6-cycloheptatrien-1-one (Eschenmoser's oxime) is proposed. The method involves redox enlargement of the ring of 4-dibromomethyl-4-methyl-2,5-cyclohexadien-1-one oxime through the action of Ni(PPh₃)₄ in DMF (in the presence of Zn). The product is formed as a mixture ofsyn- andanti-forms readily interconverting in solutions. A similar reaction of 4-methyl-4-trichloromethyl-2,5-cyclohexadien-1-one oxime afforded the dimer of agem--centered semiquinoid carbene (1,2-bis-(1-methyl-4-oxyimino-2,5-cyclohexadienyl)-1,2-dichloroethylene), together withsyn- andanti-isomers of 4-chloro-5-methyl-2,4,6-cycloheptatrien-1-one oxime, which are readily separable but also quickly interconverting in solutions. For the latter compounds, the complete¹H NMR assignment of the stereoisomeric structures has been carried out.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 519–523, March, 1995.The authors are grateful to the International Science Foundation (Grant MHW000) as well as the Russian Foundation for Basic Research (Project No. 94-03-08873) for the financial support of the work.     

Organic mass spectrometry—X. Electron impact fragmentations of alkylthio group in 2-alkylthio-5-aminothiazolo[5,4-d] pyrimidines

In order to discuss hydrogen transfer in the skeletal fragmentation of thioethers on electron impact, mass spectra of a series of 2-n-alkylthio-5-aminothiazolo [5,4-d]pyrimidines have been determined. To aid the interpretation of the hydrogen migration, deuterium-labeled compounds which are substituted with deuterium in each position of 2-n-butylthio-5-aminothiazolo-pyrimidines were studied. By correlation of the spectra obtained from such labeled compounds, the initial hydrogen migration in the fragmentation to produce [M ? SH], [MS ? CH₃] and m/e 184 ions is concluded to be as follows: migration of the α-hydrogen atom to the sulfur induces formation of the [M ? SH] ion; migration of the β-hydrogen atom to the sulfur or nitrogen atom by a McLafferty rearrangement induces formation of the m/e 184 ion; and migration of γ-hydrogen atom to the sulfur induces formation of the [M ? SCH₃] ion.