The mass spectrometric [M ? C2H4O]+ process in cyclic ketones. I—the nature of the C2H4O losss in bicyclo[3.3.1]nonan-2-one and 3-one

Although the loss of a C₂H₄O molecule from the molecular ions of the isomeric bicyclo[3.3.1]nonan-2- and 3-ones gives rise to the base peak at m/e 94 in both spectra, deuterium labelling results show that the processes leading to this ion are markedly different in the two cases. While the 2-one follows essentially (>80%) the same [M ? C₂H₄O]+ fragmentation pathway described for other 2-alkylcyclohexanones, the 3-one exhibits a more complex decomposition pathway in which one α-hydrogen is transferred away from the departing C₂ unit and three hydrogen atoms are subsequently rearranged to the eliminated C₂H₄O molecule. Similar competing fragmentation schemes have been invoked to explain deuterium labelling results in cycloheptanone, 2-methylcycloheptanone and cyclooctanone.     

Zum Mechanismus Massenspektrometrischer Fragmentierungsreaktionen. XVI—hydrid-Wanderungen bei der Fragmentierung von αω-Dimethoxyalkyl-Ionen

The isomerization and fragmentation of α,ω-dimethoxyalkyl ions a (CH₃OCH₂(CH₂)_n- CH⁺OCH₃, n = 1-6) has been investigated by deuterium labelling. It is shown that a isomerizes to ion a' by hydride transfer from the ω-CH₂ group to the positive charge at the α-C-atom before elimination of methanol. Both methoxy groups are lost as methanol. The amount of isomerization can be deduced from alkene elimination from [a ? CH₃OH]+ ions in deuterated derivatives of a. On average at 70 eV three rearrangement steps involving hydride transfer are observed.     

Fragmentation of pyrazolecarbaldehyde thio- and dithioacetals under electron impact and chemical ionization

The mass spectra of 1-substituted 3,5-dimethyl-1H-pyrazole-4-carbaldehyde bis(2-hydroxyethyl) dithioacetals and thioacetals were studied for the first time. The main fragmentation pathways of their molecular ions generated under electron impact and chemical ionization were similar. Primary decomposition of the molecular ions of bis(2-hydroxyethyl) dithioacetals involves elimination of 2-sulfanylethanol molecule with formation of the corresponding 1,3-oxathiolane radical cation. Fragmentation of the molecular ions [M]⁺ · and [M + H]⁺ derived from 2-(3,5-dimethyl-1H-pyrazol-4-yl)-1,4,6-oxadithiocanes includes cleavage of the eight-membered heteroring and elimination of C₄H₉OS ·. Substituents in the heteroring of pyrazolecarbaldehydes inhibit decomposition processes related to the aldehyde group.     

Syntheses and structures of silver(I) complexes of 4-amino-3,5-dimethyl-4<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazole and 4-amino-3,5-diethyl-4<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazole: role of the substituents

Five silver(I) adducts of 4-amino-3,5-diethyl-4H-1,2,4-triazole (4-NH₂-3,5-Et₂-tz) or 4-amino-3,5-dimethyl-4H-1,2,4-triazole (4-NH₂-3,5-Me₂-tz), namely [Ag₄(4-NH₂-3,5-Et₂-tz)₆](ClO₄)₄ (1), [Ag(4-NH₂-3,5-Et₂-tz)₂] _n ·n(ClO₄) (2), [Ag₄(4-NH₂-3,5-Et₂-tz)₆](CF₃SO₃)₄ (3), [Ag₄(4-NH₂-3,5-Me₂-tz)₆](ClO₄)₄·4H₂O (4) and [Ag₄(4-NH₂-3,5-Me₂-tz)₆](CF₃SO₃)₄·2H₂O (5), have been prepared and structurally characterised by X-ray single crystal diffraction. Two types of Ag₄tz₆ cluster have been observed in the structures of compound 1, 3, 4 and 5, which is rationalised based on the minimisation of the steric repulsions between the substituents on the 3,5-positions of triazole ring. Compound 2 displays an infinite chain structure and may be an intermediate or a minor product in the preparation.     

Synthesis of 2,6-bis(fluoroalkyl)-2,6-dihydroxytetrahydro-2<Emphasis Type="Italic">H</Emphasis>-pyran-3,5-dicarboxylates from aldehydes and fluorinated β-oxo esters in the presence of ionic liquid-K<Subscript>2</Subscript>CO<Subscript>3</Subscript> as catalytic system

An efficient procedure has been developed for the synthesis of 4-substituted 2,6-bis(fluoroalkyl)-2,6-dihydroxytetrahydro-2H-pyran-3,5-dicarboxylates by reactions of aldehydes with fluorine-containing β-oxo esters in heterogeneous catalytic system 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF₄]-K₂CO₃ activated by ultrasound. The system retains its catalytic activity for three reaction cycles.     

Metal-cinnamic acids interactions. Part IV. Synthesis,study and antimicrobial activity of copper(II) complexes of 3,4-dimethoxyhydrocinnamic acid

Summary Compounds [Cu(DPP)₂] (1), [Cu(DPP)₂H₂O]MeOH (2) (DPPH=3,4-dimethoxyhydrocinnamic acid), were synthesized and investigated by means of electronic, i.r. and room and low temperature e.s.r. spectroscopy. Compound (2) shows an e.s.r. spectrum characteristic of axially symmetric carboxylate dimers with S=1, whereas the anhydrous compound (1) shows e.s.r. features that can be interpreted if the triplet state, depending on the temperature, is able to migrate through the crystal lattice. The results for the copper(II) compounds obtained with DPPH are compared with those obtained with 3,4- and 3,5-DMCH (3,4-, and 3,5-DMCH=3,4- and 3,5-dimethoxycinnamic acid). The ligands and their complexes have been tested for antimicrobial activity.     

Mass spectrometry of γ-Complexes of transition metals : XXII. Fragmentations of ferrocenyl-substituted pyrazolines-2 under electron impact

The mass spectra of 1-N-acetyl- and 1-N-phenyl-3-ferrocenyl-5-arylpyrazolines-2, their 5-ferrocenyl-3-aryl isomers and their 3,5-diferrocenyl analogues have been studied. The “pyrazoline” type of the molecular ion fragmentation involves various processes of heterocyclic nucleus destruction and elimination of the substituents or their fragments. The directions and intensifies of the processes observed are interpreted in terms of preferred positive charge localization on the transition metal atom. Interactions between the acetyl and ferrocenyl groups manifest themselves by the appearance of intense [P  C₅H₅]⁺ ions (ferrocenyl type fragmentation products) in the mass spectra of 1-N-acetyl-3-aryl-5-ferrocenylpyrazolines-2 only. The fragmentation mechanism leading from [P  C₅H₅]⁺ to C₇H₇OFe⁺ is discussed.     

Skeletal and hydrogen rearrangements in the electron impact mass spectrum of propene

The mass spectrum of propene-2-[¹³C] shows 81% retention of C-2 in the [C₂H₃]⁺ fragment ion at 70 eV electron energy, decreasing to 75% C-2 retention at low electron energies. The mass spectra of propene-2-d₁, propene-1,1,3,3,3-d₅, propene-1,1,2-d₃ and propene-3,3,3-d₃ also have been examined at a resolution sufficient to resolve H₂-D doublets. The results at 70 eV electron energy show complete H/D randomization prior to fragmentation to form [C₃(H, D)₅]⁺ but, in agreement with the ¹³C labelling data, incomplete H/D interchange prior to fragmentation to form [C₂(H, D)₃]⁺. The results are interpreted in terms of a reversible isomerization of the propene molecular ion to a cyclopropane structure in competition with fragmentation.     

π-Conjugated soluble and fluorescent poly(thiophene-2,5-diyl)s with phenolic,hindered phenolic and p-C6H4OCH3 substituents. Preparation,optical properties,and redox reaction

Dehalogenation polycondensation of 3-(4-methoxyphenyl)-2,5-dibromothiophene with Mg and a zerovalent nickel complex as well as chemical oxidative polymerization of 3-(4-methoxyphenyl)thiophene with FeCl₃ gives poly[3-(4-methoxyphenyl)thiophene-2,5-diyl] P3(4-MeOPh)Th. Treatment of soluble P3(4-MeOPh)Th with BBr₃ converts the OCH₃ group to an OH group and gives poly[3-(4-hydroxyphenyl)thiophene-2,5-diyl] P3(4-OHPh)Th. Oxidative polymerization of 3-[3,5-di-t-butyl-4-{(trimethylsilyl)oxy}phenyl]thiophene with FeCl₃ in an aqueous medium directly affords another kind of polythiophene with a sterically hindered phenolic group, poly[3-(3,5-di-t-butyl-4-hydroxyphenyl)thiophene-2,5-diyl] P3(4-OH-3,5-tBu₂Ph)Th. An organometallic dehalogenation polymerization using a nickel complex also affords P3(4-OH-3,5-tBu₂Ph)Th. All the polymers described above show strong photoluminescence in a region of 500–600 nm. Oxidation of P3(4-OH-3,5-tBu₂Ph)Th with PbO₂ gives stable radical species as confirmed by IR and ESR spectroscopy. Electrochemical redox behavior of the polymers is compared with that of other polythiophenes. © 1997 John Wiley & Sons, Inc.     

Hydrogen migrations in mass spectrometry. II—single and double hydrogen migrations in the electron impact fragmentation of n-propyl benzoate

The sources of the migrant hydrogen atom(s) in reactions (a) and (b) in the electron impact mass spectrum of n-propyl benzoate have been investigated: (a) [C₆H₅CO₂C₃H₇]⁺ →[C₆H₅CO₂H]⁺ + C₃H₆; (b) [C₆H₅CO₂C₃H₇]⁺ → [C₆H₅CO₂H₂]⁺ + C₃H₅^sdot;. Deuterium labelling of the propyl group showed that, for reaction (a) at 70 eV ionizing energy 3 ± 1% of the hydrogen originates from C-1 of the propyl group, 86 ± 4% from C-2 and 11 ± 3% from C-3. The specificity of the transfer from C-2 increases as the internal energy of the fragmenting ions decreases, indicating that the results cannot be rationalized in terms of H/D interchanges between positions in the propyl group, but rather that the reaction involves specific, competing, H transfer reactions from each propyl position, in contrast to the high site specificity characteristic of the McLafferty rearrangement. Reaction (b) involves, almost exclusively, transfer of one hydrogen from C-2 and one from C-3 with only very minor participation of C-1 hydrogens. The [C₆H₅COOH]⁺ ion produced in reaction (a) fragments further to [C₆H₅CO]⁺ + OH. and the labelling results indicate some interchange of the carboxylic hydrogen with (ortho) ring hydrogens for those ions fragmenting in the first drift region. The extent of interchange is less than that observed for fragmentation of the same ion produced by direct ionization of benzoic acid or by reaction (a) in ethyl benzoate.     

Mass spectrometry of heterocyclic compounds—II: Electron-impact induced fragmentation of 3,5-diphenyl-1,2,4-oxadiazole

The electron-impact induced fragmentation of 3,5-diphenyl-1,2,4-oxadiazole has been investigated by labelling experiments, defocused metastable ion detections and high resolution mass measurements. The main fragmentation process suggests heterocyclic cleavage at the 1 to 5 and 3 to 4 bonds confirming our previous interpretation. The structure of the major fragment ion [C₇H₅NO]⁺· has been interpreted as being represented by the isomeric benzonitrile oxide and phenylisocyanate structures, the latter isomerising irreversibly from the former. The benzonitrile oxide structure is consistent with [C₇H₅NO]⁺· formation by cleavage of the 1 to 5 and 3 to 4 bonds.     

Stereoselective Synthesis of (3R)‐3,4‐Dihydro‐6,8‐dimethoxy‐3‐undecyl‐ 1H‐[2]benzopyran‐1‐one and Derivatives,Metabolites from Ononis natrix

A short stereoselective synthesis of (3R)‐3,4‐dihydro‐6,8‐dimethoxy‐3‐undecyl‐1H‐[2]benzopyran‐1‐one and derivatives isolated from Ononis natrix has been described. Condensation of dodecanoyl chloride with 3,5‐dimethoxyhomophthalic acid afforded 6,8‐dimethoxy‐3‐undecylisocoumarin 3 , which, on sequential saponification and esterification, yielded the keto ester 5 . Enantioselective reduction of 5 with TarB‐NO₂/LiBH₄ directly furnished the title dihydroisocoumarin 1a in 80% ee (82% yield). Partial as well as complete demethylation of the latter provided the dihydroisocoumarins 1b and 1c , respectively. Diastereotopy of the CH₂ H‐atoms on either side of the stereogenic center (C(3)) and the mass‐fragmentation pattern of the dihydroisocoumarins have also been described. All of the compounds synthesized were examined in vitro for antifungal activity.     

Conjugated Schiff's bases 16—Substituent effect on electron impact fragmentation of some 1-oxa-4-azabutadienes1

The electron impact fragmentation patterns of some 1-oxa-4-azabutadienes have been determined and supported by the corresponding metastables. The effect of substituents on this fragmentation has been investigated. Satisfactory correlation of intensity ratios of the peaks characterizing the primary fragmentation versus the Brown and Okamoto σ⁺ substituent parameters has been found. The relationship between the substituent parameters and the dissociation energy E_D,C(3)-C(5), estimated with the help of appearance energies has been considered.     

Tetrazole compounds. 11. electron impact mass spectrometry of 1-aryl-5-(l-acyl-2-dialkylaminovinyl)-1H-tetrazoles

The mass spectrometric behaviour of 1-aryl-5-(1-acyl-2-dialkylaminovinyl)-1H-tetrazoles was studied, especially using 1-phenyl-5-(1-benzoyl-2-dimethylaminovinyl)-1H-tetrazole 1 and its D-and ¹⁵N-labeled derivatives. All tetrazoles investigated showed a clearly observable molecular ion and underwent as the main fragmentation the elimination of nitrogen followed by a number of various subsequent processes. Besides, primary fragments such as [M ? N₃^?]⁺ and [M — ArN₃]^+? were also observed.     

Phospha-s-triazines II. Mass spectra of mono(diarylphospha)-s-triazines

Electron impact fragmentation patterns were obtained for 1-dephenylphospha-3,5-bis(perfluoro-n-heptyl)-2,4,6-triazine, 1-diphenylphospha-3,5-bis[C₃F₇(OCF(CF₃)CF₂)_xOCF(CF₃]-2,4,6-triazine (x=1 and 2) and their pentafluorophenyl analogues. In each instance the ion R₂PN₂C⁺ (RC₆H₅ or C₆F₅) constituted the base peak. Based on the observed metastable peaks, fragmentation pathways leading to the formation of this and other significant ions are postulated and similarities to s-triazine and diphenyl phosphazene trimer breakdown patterns are discussed.     

Energetische Betrachtungen zur Intramolekularen Solvatisierung von Ionen bei der Elektronenstoss-Induzierten Fragmentierung von α,ω-Bis-(Trimethylsilyl)-Äthern

By means of AP measurements it has been shown that the stable [M? CH3]+ ions from α,ω-bis(trimethylsilyl) ethers of the type TMS? o? (CH₂)_n? O? TMS (n = 2 to 7) do not possess a cyclic structure.     

Zum Mechanismus Massenspektrometrischer Fragmentierungsreaktionen—V: Substituenteneffekte auf Intramolekulare Substitutionen des Phenylrestes in den Massenspektren von N,N-Dimethyl-N′-Phenylformamidinen

The mass spectrum of N,N-dimethyl-N′-phenyl-formamidine (I) contains a large peak due to [M ? H]+-ions. As is shown by deuterium labelling, one of the ortho hydrogen atoms of the phenyl group is lost. The same result has been observed for the corresponding fragmentation of thioformanilide (V). This can be explained by the formation of benzimidazolium-ions (a). The effect of substituents at the phenyl group on the intensities and AP of these ions and on the IP of the molecular ions has been investigated. A mechanism of the cyclization reaction is proposed.     

A novel dinuclear MoVI complex with tris(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)methane

Recrystallization of [MoO₂Cl{HC(3,5‐Me₂pz)₃}]Cl [where HC(3,5‐Me₂pz)₃ is tris(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)methane] led to the isolation of large quantities of the dinuclear complex dichlorido‐2κ²Cl‐μ‐oxido‐κ²O:O‐tetraoxido‐1κ²O,2κ²O‐[tris(3,5‐dimethyl‐1H‐pyrazol‐1‐yl‐1κN²)methane]dimolybdenum(IV) acetonitrile monosolvate, [Mo₂Cl₂O₄(C₁₆H₂₂N₆)]·CH₃CN or [{MoO₂Cl₂}(μ₂‐O){MoO₂[HC(3,5‐Me₂pz)₃]}]·CH₃CN. At 150 K, this complex cocrystallizes in the orthorhombic space group Pbcm with an acetonitrile molecule. The complex has mirror symmetry: only half of the complex constitutes the asymmetric unit and all the heavy elements (namely Mo and Cl) are located on the mirror plane. The acetonitrile molecule also lies on a mirror plane. The two crystallographically independent Mo⁶⁺ centres have drastically different coordination environments: while one Mo atom is hexacoordinated and chelated to HC(3,5‐Me₂pz)₃ (which occupies one face of the octahedron), the other Mo atom is instead pentacoordinated, having two chloride anions in the apical positions of the distorted trigonal bipyramid. This latter coordination mode of Mo^VI was found to be unprecedented. Individual complexes and solvent molecules are close‐packed in the solid state, mediated by various supramolecular contacts.     

Multifunctional iron thiocarboxylate complexes: synthesis,reactivity and structure of CpFe(CO)<Subscript>2</Subscript>SCO-3,5-C<Subscript>6</Subscript>H<Subscript>4</Subscript>(COCl)<Subscript>2</Subscript>

A controlled substitution reaction of the chlorine atoms of 1,3,5-benzenetricarbonyl trichloride by the organoiron fragment (CpFe(CO)₂S) has been achieved. The complexes CpFe(CO)₂SCO-3,5-C₆H₃(COCl)₂ (1), 1,3-[CpFe(CO)₂SCO]₂-5-C₆H₃COCl (2) and 1,3,5-[CpFe(CO)₂SCO]₃C₆H₃ (3) were prepared from the reaction of (μ-S _x )[CpFe(CO)₂]₂ (x = 3, 4) with 1,3,5-C₆H₃(COCl)₃ in a 1:1, 2:1, or 3:1 metal to ligand molar ratio. The reactions of (1) with amines, thiols, and carboxylic acids produce the trifunctional mono-iron complexes CpFe(CO)₂SCO-3,5-C₆H₃(COY)₂ [Y = NR₂ (4), SR (5), OCOR (4)]. The X-ray structure determination of (1) is reported.     

Copper(II) complexes with <Emphasis Type="Italic">N</Emphasis>-(phenyl)alkylthiosemicarbazones of 3,5-dichloro- and 3,5-diiodosalicylic aldehydes

N-(Phenyl)alkylthiosemicarbazones of 3,5-dichloro- and 3,5-diiodosalicylic aldehydes (H₂L) and their copper(II) complexes [Cu(HL)(CH₃OH)]⁺(NO₃)^– have been synthesized. The structure of one of the complexes has been determined by X-ray analysis.