Synthesis and structure of the N-alkyl-2,6-dimethyl-4-oxopyridine-3-carboxylic acids

A range of N-alkyl-2,6-dimethyl-4-oxopyridine-3-carboxylic acids XV have been prepared via reactions of primary alkyl amines with differing 2,6-dimethyl-4-oxopyran-3-carboxylate esters IX . The quantity of desired product formed and the character of by-products formed are determined by the natures of the amine and ester IX respectively. X-ray crystallography data for the N-ethyl analogue of XV indicates very strong intramolecular hydrogen bonding to be present, with the heterocyclic ring exhibiting considerable aromaticity.     

Synthesis of pyrrole-2-carboxylic acids and their N-vinyl derivatives

Haloform cleavage of 2-trifluoroacetyl- and N-vinyl-2-trifluoroacetylpyrroles gives pyrrole-2-carboxylic acids and their N-vinyl derivatives in good yields; most of these compounds do not melt between 120–190C, but rather decompose with CO₂ evolution.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 612–616, May, 1990.     

New data on derivatives of 1-alkoxyaziridine-2-carboxylic acids

Esters of β-alkoxyamino-α-bromopropionic acids were obtained by reaction of α,β-dibromopropionic acid esters with alkoxyamines in the presence of triethylamine at 20°C for 1 month. When the products are refluxed in acetonitrile in the presence of triethylamine, they are converted to aziridines. Selective amidation of the alkoxyaziridines with excess dimethylamine in absolute methanol in the presence of sodium methoxide leads to enrichment with the cis isomer. The parameters of inversion of the nitrogen atom in the alkoxyaziridines were determined. Communication 20 from the series “Asymetric Unbridged Nitrogen”; see [1] for communication 19. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 212–215. February, 1980.     

Absolute configuration of diastereomeric derivatives of N-substituted aziridine-2-carboxylic acids

Individual diastereomers of a number of anilides of N-substituted aziridine-2-carboxylic acids have been obtained. Conclusions regarding the spatial structure of the compounds indicated have been drawn on the basis of the ¹H NMR, ¹⁵N NMR, and CD spectra.Report 37 of the series entitled Asymmetric nonbridging nitrogen. For report 36 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1343–1348, October, 1984.     

O-trimethylsilylquinoxalinol derivatives of aromatic alpha-keto acids. Mass spectra and quantitative gas chromatography

As an extension of earlier work on aliphatic alpha-keto acids, a method is described for the quantitative gas chromatographic determination of urinary aromatic alpha-keto acids. The keto acids are derivatized with o-phenylenediamine to yield the quinoxalinols. These compounds are chromatographed after trimethylsilylation. The aromatic keto acids are stabilized by sodium dithionite (4 mg/ml urine) and storage below 0 degrees. The final derivatives are stable for weeks at room temperature. Low resolution mass spectra are reported. The fragmentation mechanisms are elucidated by analysis of O-trimethylsilyl-(TMS)-quinoxalinois, O-(TMS-d9)-quinoxalinois and O-TMS-6(7)-chloroquinoxalinois.     

Mass spectra of benzoxazolone derivatives

N-Acetonylbenzoxazolones containing a substituent in the acetonyl residue, as well as their hydrazones and oximes, decompose under the influence of electron impact to give primarily fragments of N-methylene- or N-methylbenzoxazolones. For the oximes and hydrazones the characteristic ions are (M -OH) and (M — NH₂), which evidently have cyclic structures. The isomeric aryl triazinones undergo fragmentation via the scheme of the retrodiene synthesis. The characteristic ions that make it possible to distinguish the isomeric benzoxazolones, arylimidazolones, and aryltriazinones were found.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1493–1497, November, 1976.     

Mass spectra of phenoxyacetyl derivatives

The electron-impact-induced mass spectra of substituted N-phenylphenoxyacetamides are discussed. The structure of the rearrangement ion at m/z 108 is investigated and compared with the molecular ion of anisole by metastable ion and corrected collisionally activated dissociation spectra.     

Mass spectra of nucleoside derivatives

The mass spectra of derivatives of uridine, adenosine, cytidine and guanosine are recorded. Derivatization techniques include permethylation, acetylation, trifluoroacetylation, trimethylsilylation and the synthesis of 2′,3′-O-isopropylidenes and 2′,3′-O-phenylboronic esters. Sequential derivatization by a selective combination of some of these procedures results in nucleosides which are blocked with a characteristic group at the cis 1,2 diol position, and, which contain other substituent groups that enhance the volatility of the compound. The specific substitution at the cis-glycol region has been shown to be particularly useful in asymmetrically derivatizing dinucleoside phosphates since certain fragment ions from their mass spectra indicate the sequence of the two nucleoside components. Sequence isomers such as adenylyl-(3′-5′)-uridine and uridylyl-(3′-5′)-adenosine can be unambiguously distinguished.     

2-aryl-5-arylsulfanyl-1,3-oxazole-4-carboxylic acids and their derivatives

A convenient preparative procedure has been developed for the synthesis of previously unknown 2-aryl-5-arylsulfanyl-1,3-oxazole-4-carboxylic acids and their functional derivatives from accessible multicenter substrates of the general formula Cl₂C=C(NHCOR)C(O)OMe. The products turned out to be suitable for various subsequent transformations. Some oxazole-4-carboxylic acid hydrazide derivatives containing a substituted oxazol-5-yl fragment at the N² atom in the hydrazine moiety underwent recyclization on heating in acetic acid; as a result, one oxazole ring was converted into 1,3,4-oxadiazole.     

Mass spectra of pyrazino- and piperazinoindole derivatives

The behavior of compounds of the pyrazino- and piperazinoindole series under the influence of electron impact was studied. The fragmentation was examined as a function of the type of substituents attached to the nitrogen atom in the piperazine ring and the degree of saturation of the condensed rings. Deuterium labeling and model analogs were used to prove the fragmentation mechanisms. It is shown that the positive charge in the molecular and fragment ions may be localized both on the bridge nitrogen atom of the indole ring and on the N atoms of the pyrazine or piperazine ring. The characteristic fragments for each type of compound were found. The results can be used to study the structures of new derivatives of pyrazino- and piperazinoindoles or the products of their metabolism.Communication VII from the series Application of mass spectrometry in structural and stereochemical investigations. See [1] for communication VI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 827–832, June, 1978.     

Mass spectra of some oxadiazole derivatives

The mass spectra of some substituted oxadiazoles have been determined and analysed with the aid of high resolution mass spectrometry. Some characteristic and major differences between their spectra have been noted, and possible rationalizations have been advanced. The main fragmentation patterns of the 1,3,4-oxadiazole derivatives have been interpreted in terms of diazirine intermediates. Specific skeletal rearrangement processes have been observed in the spectra of the 1,3,4- and 1,2,4-oxadiazoles, and possible mechanisms are proposed.     

Mass spectra of some neopentylphosphorus derivatives

The fragmentation patterns and major metastable ions of the mass spectra of the neopentyl-phosphorus derivatives [(CH₃)₃CCH₂]₃P, [(CH₃)₃CCH₂]₂P(O)H, [(CH₃)₃CCH₂]_nPX_3-n (n = 1 and 2; X = H, Cl, C₆H₅ and CH = CH₂), [(CH₃)₃CCH₂]₃PS, [(CH₃)₃CCH₂]_nP(S)R_3-n (n = 1 and 2; R = C₆H₅ and CH = CH₂), [(CH₃)₃ CCH₂]₂PCH₂CH₂P[CH₂C(CH₃)₃]₂, ([CH₃)₃CCH₂]₂PCH₂PCH₂-CH₂P(H)C₆H₅ and [(CH₃)₃CCH₂]₂PCH₂CH₂P(S)(CH₃)₂ are described. Fragmentation of a neopentyl group by elimination of either C₄H₈ or CH₃ is very favourable when the neopentyl group is bonded to either a tricoordinate or tetracoordinate phosphorus atom. In neopentylphosphines with two or three neopentyl groups, stepwise elimination of C₄H₈ from all of the neopentyl groups occurs very readily. The resulting [(CH₃)_nPX]^+._3-n ions are often the most intense ions in the mass spectra.     

三羰基铬苯乙烯甲酰衍生物的质谱研究

含有α、β不饱和酮和酰胺的三羰基铬芳基配合物的质谱未见有详细报道,本文报道标题化合物电子轰击(EI)质谱,并利用高分辨质谱数据和MS/MS联用技术探讨其裂解机理,观察到R基团的重排反应和在不同汽化温度下发生的双分子裂解反应和氢化反应等。