Mass spectra of some alkyl isoxazoles

The mass spectra of several compounds obtained during the process of Stork's isoxazole synthesis9 as well as the related isoxazoles have been investigated. The fragmentations of simple alkyl isoxazoles are nicely formulated via azirine intermediates. A striking difference between the spectra of isoxazoles and those of methylfurans as to the relative abundance of [M — l] peaks is noteworthy. The very low abundance of these peaks in the former reflects the unique character of isoxazole nucleus due to the preferential cleavage of N? O linkage rather than a benzylic C? H bond rupture. If an alkyl substituent is present at 4-position in 3,5-dimethylisoxazoles, strong peaks at m/e 110, 68 and 43 are common in their spectra. The analyses of metastable transitions and high resolution measurements have demonstrated that the formation of these ions can be interpreted by a mechanism involving the cleavage of N? O linkage.     

Trialkyl- and trialkoxy(trifluoroacetoxy alkyl)silanes

Conclusions A method was developed for the synthesis of trialkyl- and trialkoxy(trifluoroacetoxyalkyl)silanes, which is based on the reaction of the corresponding iodoalkyl or bromoalkyl derivatives with silver trifluoroacetate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1170–1172, May, 1978.     

Reaction of chloromethylalkoxysilanes with N-phenylaminoethoxy (alkyl) silanes

Conclusions bis-(N-Phenyl-2-aminoethoxy)dimethylsilane reacts with chloromethylalkoxysilanes to yield cyclic substitution products with the isolation of dimethyldimethoxysilane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 392–396, February, 1970.     

NMR spectra of some alkyl(oxinato)tin(IV) complexes

Proton magnetic resonance spectra of a series of alkyl(oxinato)tin(IV) complexes, alkyl(oxinato)thallium(III), dimethylbis(oxinato)lead(IV), 8-methoxyquinoline, 2-methyl-8-hydroxyquinoline and 8-hydroxyquinoline were studied. The indirect spin-spin coupling constants J₂₃, J₃₄ and J₂₄ of the oxinato ligand in the alkyl(oxinato)tin(IV) complexes and of 8-methoxyquinoline were found to be 4.4 ± 0.2, 8.3 ± 0.2 and 1.7 ± 0.2 Hz, respectively. When the interaction between tin and nitrogen in the oxinato ligand is not strong as in trialkyl(oxinato)tin(IV), the resonance of the 2-proton of the ligand shifts to high magnetic field relative to that of 8-methoxyquinoline, but in the case of the strong interaction, as in dimethyl(oxinato)halogenotin(IV), the resonance is shifted to low magnetic field. The 4-proton signals, however, shift monotonously to low magnetic field with increasing interaction. The behaviour of the 2-proton signals was explained by a paramagnetic anisotropic effect of a nitrogen lone pair of the oxinato ligand and an intramolecular electric field effect and that of the 4-proton by the latter effect. By comparing the change of the δ-values of the 2-, 3- and 4-protons of the alkyl(oxinato)tin(IV) complexes and those of 8-hydroxyquinoline by altering the solvents, from methylene chloride to benzene, it was found that the electron density around the 2-carbon is reduced in the complexes compared with that of 8-hydroxyquinoline.     

The mass spectra of some tris(trimethylsilyl)acylsilanes and tris(trimethylsilyl)silanes

While tris(trimethylsilyl) alkanoylsilanes fragment in the acylsilane form yielding [(Me₃Si)₃SiCO]⁺ by α-cleavage, the molecular ions of their aryl counterparts rearrange to ionized silaethenes prior to cleavage, paralleling known photochemical behaviour. Sila-allyl type structures are attributed to the stable [M? Me˙]⁺ ions obtained by subsequent cleavage. Metastable ion characteristics reveal the identity of the structures of the monomeric silaethene ions obtained from one of the aroylsilanes and a 1,2-disilacyclobutane. The non-compliance of the alkanoylsilanes with their photochemical behaviour is attributed to a preferred elimination of the stable alkyl radical (R˙) from the molecular ions. Several polysilanes display abundant odd-electron ions which may possess a disilene structure.     

Mass spectra and three-dimensional structures of γ-N-aryl(alkyl)aminopiperidines

The fragmentation of the investigated compounds proceeds with both retention and cleavage of the piperidine ring and makes it possible to distinguish the spatial orientation of the methyl group in the C₍₅₎ position of the ring in the analysis of the geometrical isomers of this series.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 813–818, June, 1988.     

Preparation of high molecular weight poly(vinylaniline)

For the first time, we believe, a high molecular weight soluble poly(vinylaniline) has been prepared. This was done by a bead polymerization with exclusion of oxygen. The polymer has little or no color and good stability in solution.     

Mass spectra of some azoles

The principal electron-impact fragmentation patterns of 3,4,5-triphenyl-1,2,4-triazole, 2,5-diphenyl-1,3,4-thiadiazole, their perfluorinated analogues and 2,5-di(pentafluorophenyl)-1,3,4-oxadiazole have been established from metastable ion evidence and precise mass measurements. Although ions produced by expulsion of nitrogen from the molecular-ions of these compounds are of low abundance, the simultaneous expulsion of nitrogen and a C₇X₅ radical (X = H or F) gives rise to abundant ions.     

Mass spectra of some furanosesquiterpenes

Some of the fragmentation modes operating in a few furanosesquiterpenes have been established from accurate mass measurements and metastable data.     

Mass spectra of some silylaryladamantanes

Conclusions The molecular weight and the number and nature of the substituents, and also their position, can be determined from the mass spectra of silylaryladamantanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 707–708, March, 1982.     

Mass spectra of some diazadiamides

Electron impact mass spectra at nominally low electron energies are reported for a series of diazadiamides. Diazadiamides are of interest because of their use as ligands in transition metal complexes.     

Mass spectra of some thionocarbamates

The mass spectra of a number O-alkylthionocarbamates with two, one or no alkyl substituents on the nitrogen atom are presented and discussed. The main primary fragmentation pathways are McLafferty rearrangements, including the double so-called protonated McLafferty rearrangement. Generally, rearrangement products give charge delocalized ions, which release hydroxyl or sulphydryl radicals and water or hydrogen sulphide, to produce stable fragments. It has been found that the position of alkyl moieties may be deduced on the basis of mass spectral fragmentation patterns.     

Mass spectra of steroidal alkyl ethers—I

The mass spectral fragmentation of saturated and unsaturated steroidal methyl and ethyl ethers and ethers of 4,4-dimethyl steroids are studied and compared to the fragmentation of steroidal alcohols, trimethylsilyl ethers and ethylene ketals. Unlike the trimethylsilyl ether the small fragment containing the alkoxy group is neither the base peak nor a very strong peak in the spectrum. A significant peak occurs at [M — ROH]^+·, however, sometimes even constituting the base peak of the spectrum. The fragmentations of the alkyl ethers are largely dependent on their environments. The present results also show the generalization that methyl ethers are better leaving groups than the corresponding alcohols in fragmentation processes, is not always valid.     

Mass spectra of some steroidal diols

The mass spectral fragmentations of a number of steroidal 3,5- and 4,5-diols and some derivatives have been examined using high resolution mass spectrometry and deuterium labelling. Although the 3,5- and 4,5-diols have very similar mass spectra those of the derived ketols are quite characteristic. A pathway for the formation of the important m/e 332 ion in the mass spectrum of cholestan-4β,5α-diol has been postulated.