The mass spectra of some para substituted triarylphosphines and triarylphosphine oxides

The mass spectra are reported for a series of tris(p-alkylaryl)phosphines and the corresponding phosphine oxides. The phosphines all give [M]^+˙ as the base peak except when the phenyl groups are not para substituted. For the oxides [M–H]⁺ gives the base peak with one exception for which [M]^+˙ is the most abundant ion.     

Phosphorylation of (1-aryl-1-hydroxymethyl)phosphonates

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The mass spectra of some substituted thiophene-2-carboxanilides

The mass spectra of some substituted thiophene-2-carboxanilides at 70 eV are reported. The primary degradation reaction of these compounds involves cleavage of the amide bond, followed by elimination of CO. The effect of substituents on the mass spectra are related by the Hammett equation. The correlation against σ and σ⁺ is poor.     

The mass spectra of some vicinally substituted nitropyridines

The fragmentation behaviour of 22 vicinally substituted nitropyridines has been studied under electron impact conditions. The decomposition patterns were found to be strongly affected by interaction of the substituent with the nitro group and the ring nitrogen. AH fragmentation sequences depend to a great extent on the position of the substituent in the ring.     

General synthesis of 8-aryl-2-tetralones

Two alternative routes are described for the synthesis of 8-aryl-2-tetralones (1). Route A starts from alpha-tetralone 3 and involves 3 or 4 steps, with the selective Na-EtOH reduction of 1-aryl-7-methoxynaphthalenes 2 being the key step. The exclusive reduction of the A ring of naphthalenes 2 occurs when the aryl group at C-1 has no substituent at the ortho positions, affording tetrahydronaphthalenes 11. Reduction of the B ring of 2 becomes the major process when the aryl fragment has two substituents at the ortho positions, affording 8-aryl-2-tetralones 1 as the major component. Route B involves 5 steps starting from 2-tetralone 5, with the key step being the Suzuki coupling with triflate 4. This approach allows the synthesis of 8-aryl-2-tetralones 1 with no substituent at the ortho positions of the aryl fragment and with naphthalene and anthracene rings at C-8.     

The mass spectra of substituted 2-methylbenzophenones

The mass spectra of some methoxy and methyl derivatives of 2-methylbenzophenone have been examined. Loss of a substituents from 3′-and 4′-positions as well as the previously known loss from 2′-positions are important fragmentation processes. Thus, these fragmentations are of little use in locating substituents on benzophenones of unknown structure. Deuterium labelling shows the [M - 1]⁺ ion from 3′,4,4′,5,5′-pentamethoxy-2-methyl benzophenone to be due largely to loss of hydrogen from 2′- and 6′-positions.     

Synthesis of some substituted 1-(2-propynyl)-4-piperidones

Summary Some 1-(1,2-dimethyl-2-propynyl)-4-piperidones were synthesized, and the effect of substitution in the piperidine ring on the reversible cyclization of unsaturated-alkylamino ketones into 4-piperidones was investigated.     

Chemical ionization and electron impact mass spectra of alicyclic substituted 2-aryl-1,3-dithianes

The methane and isobutane chemical ionization mass spectra of alicyclic substituted 2-aryl-1,3-dithianes were examined by gas chromatography mass spectrometry. The protonated molecular ion was found to be of low abundance in the methane spectra, while a protonated cyclic sulfide cation (m/z 107) appeared as the base peak. A protonated molecular ion was the base peak when isobutane was used as the reagent gas. Electron impact mass spectra displayed weak molecular ions and were characterized by the m/z 106 fragment.     

The mass spectra of some 2- and 4-pyridylethylamines

The mass spectra of some N,N-disubstituted 2-aminoethylpyridines are reported and their principle fragmentation routes analysed.     

The structures of 2-(4,5-dihydro-5-aryl-3-isoxazolyl)-1-arylethanone oximes. An unusual behaviour in its 1H-NMR and mass spectra

The reaction of dibenzalacetones substituted on the aromatic ring with hydroxylamine hydrochloride and potassium hydroxide in refluxing ethanol affords several compounds. Herein, we report the structures and spectral properties of several oximes of 2-(4,5-dihydro-5-aryl-3-isoxazolyl)-1-arylethanones 6 . Unusual behaviour on its ¹H-nmr and mass spectra was observed. Single crystal X-ray diffraction was performed on compound 6d to support our structural considerations abouth the title compounds.     

A concise synthesis of 2-benzoyl-1-indanones and 1-indanones from 2-aryl-1-tetralones

Abstract

Methyl-2-(3-oxo-3-aryl) benzoates derived from acid catalyzed air oxidative fragmentation of 2-aryl-1-tetralones were efficiently undergone intramolecular-Claisen condensation in the presence of potassium tertiary butoxide. The resulting 2-benzoyl-1-indanones formed in two-step ring contractions were further subjected to indium triflate mediated retro-Claisen condensation to get 1-indanones.     

The mass spectra of 1- and 2-alkylbenzotriazoles

The fragmentation patterns of a series of 1- and 2-alkylbenzotriazoles are recorded and interpreted in comparison with available literature data. 1- and 2-Substituted benzotriazoles are readily differentiated on the basis of the relative ease with which a 1-substituted isomer loses nitrogen compared with the corresponding 2-isomer, resulting in generally weak parent ions for the former and strong parent ions for the latter. This loss of nitrogen in the 1-isomer ultimately gives rise to a strong peak at m/z 104, which is small or absent in the 2-isomer. In addition, examination of the intensity and distribution of peaks clustered around m/z 118 reveals that weak signals with a maximum intensity at m/z 117 or 118 are indicative of the 1-isomers, while strong signals with a maximum intensity at 119 or 120 are typical of the 2-isomers. Thus, isomers are distinguished by analysis of mass spectral cracking patterns. © 1997 John Wiley & Sons, Inc. Heteroatom Chem. 8: 459–464, 1997     

Negative and positive mass spectra of some substituted trinitromethanes

The negative and positive ion mass spectra of a series of substituted trinitroalkanes (nitroform, tetranitro methane, methyl, fluoro, chloro, bromo and iodo-trinitro methane) have been measured with an Aatlas CH-4 Mass Spectrometer, under varying electron energies from 70 over the total range at which ions are produced. The modes of decomposition of the compounds are presented. A few metastable transitions are observable in the negative ion spectra, but only at high electron energies (ion pair region) and are very low in intensity. the negative and positive ion clastograms of these polynitro compounds showed little parent-daughter ion correlation. Finally, the negative ions formed appear to contain excess amounts of kinetic energy even at low electron energies; as a retult there is a great deal of overlap in the various mechanisms for the formation of negative ions.     

Electron impact mass spectra of 1-methyl-3-(2-benzothiazolylhydrazono)-2-indolinones

A study of the fragmentation of l-methyl-3-(2-benzothiazolylhydrazono)-2-indolinones on electron impact reveals that the major processes involve N? N bond fission and the competing loss of CO from the molecular ion.     

Transformation of trans-4-aryl-3-chloro-1-(2-chloroethyl)azetidin-2-ones into 3-aryl-2-(ethylamino)propan-1-ols via intermediate 1-(1-aryl-2-chloro-3-hydroxypropyl)aziridines and trans-2-aryl-3-(hydroxymethyl)aziridines

trans-4-Aryl-3-chloro-1-(2-chloroethyl)azetidin-2-ones, prepared through cyclocondensation of chloroketene and the appropriate imines in a diastereoselective way, were unexpectedly transformed into 3-aryl-2-(ethylamino)propan-1-ols using LiAlH(4) in THF under reflux. A stepwise analysis showed that the initially formed 1-(1-aryl-2-chloro-3-hydroxypropyl)aziridines were converted into trans-2-aryl-3-(hydroxymethyl)aziridines, most probably via N-spiro bis-aziridinium intermediates, which were subsequently prone to undergo ring opening by LiAlH(4) to afford 3-aryl-2-(ethylamino)propan-1-ols.