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1.
Josef Emmeram Schachtner Thomas Zoukas Hans-Dietrich Stachel Kurt Polborn Heinrich Nth 《Journal of heterocyclic chemistry》1999,36(1):161-175
1,2-Dithiolopyrrolones and their heterologues of type 1 are resonance stabilized systems displaying a high dipole moment. Upon oxidation with organic peracids compounds 2 , 5 , 15a, 16a, 20a and 25a gave the corresponding S(2)-oxides and, depending on substituents, in some cases the S(2)- and S(1)-dioxides. The S(2)-monoxides showed a proclivity to disproportionation and were easily reduced to dithioles with symme trical dimethylhydrazine. From S(2)-oxides and several primary amines bicyclic isothiazole-S-oxides were obtained (S/N-exchange reaction). From the N-unsubstituted isothiazole S-oxide 10e the N-hydroxyisothiazole 9d was synthesized by an aza-Pummerer-type rearrangement. The assumption is made that S(2)-oxides may be biologically important as active metabolites of pyrrothines and analogues of type 1 in their action as antibacterials and antimycobacterials. 相似文献
2.
N. Soundararajan R. Palaniappan V. T. Ramakrishnan T. K. Thiruvengadam K. Kanakarajan K. Natarajan P. Shanmugam 《Journal of mass spectrometry : JMS》1980,15(12):651-658
A study has been made of the fragmentation upon electron impact of thieno(2,3-b)quinoline and sixteen of its derivatives containing methoxy, methylenedioxy, chloro, bromo, iodo, nitro and methyl substituents. Besides these, the fragmentation patterns of some S-oxides, and S,S-dioxides were also investigated. The majority of the spectra contain molecular ions and the principal fragmentation routes involve loss of carbon monosulphide and hydrogen cyanide from the molecular ion. Rearrangement of the molecular ion appears to precede the fragmentation process in the case of S,S-dioxides. The fragmentation of 4-methylthieno(2,3-b)quinoline is closely analogous to that of alkylquinolines. The main features of these spectra can be predicted from the fragmentation pathways proposed for the parent thieno(2,3-b)quinoline. 相似文献
3.
The characteristic fragmentation pattern in the mass spectra of 4-oxo-4H-pyrazole 1-oxides and 4-oxo-4H-pyrazole 1,2-dioxides involves scission of the ring into two fragments by cleavage of the nitrogen-nitrogen bond and one of the bonds to the carbonyl carbon. Loss of carbon monoxide or oxygen from the molecular ion is not observed. 相似文献
4.
The 17O chemical shift data for a series of azine N-oxides, diazine N-oxides and di-N-oxides at natural abundance are reported. Isomeric methyl substituted quinoline N-oxides exhibited chemical shifts which are interpreted in terms of electronic and compressional effects. The 17O chemical shift for 8-methylquinoline N-oxide (370 ppm) is deshielded by 25 ppm more than predicted, based upon electronic considerations. The 17O chemical shift for the N-oxide of 8-hydroxyquinoline (289 ppm) is substantially shielded as a result of intramolecular hydrogen bonding. The relative 17O chemical shifts for diazine N-oxides of pyrazine, pyridazine and pyrimidine follow predictions based on back donation considerations. Because of solubility limitations, spectra of only two N,N′-dioxides were obtained. The chemical shift of benzopyrazine di N-oxide in acetonitrile was shielded by 18 ppm compared to that of its mono N-oxide. 相似文献
5.
Silvana M. de Oliveira Wagner F. de Giovani Jos Ricardo Romero Joseph Miller 《Journal of mass spectrometry : JMS》1991,26(10):855-856
Mass spectra of picolinic, nicotinie and isonicotinie acids and of their respective N-oxides are presented. Picolinic acid and its N-oxide demonstrate the facile loss of carbon dioxide and low-intensity molecular ions. Fragmentation is relatively simple. Nicotiuic and isonicotinic acids show very similar fragmentation patterns. For both, the molecular ion is the base peak. The fragmentations of nicotinic acid N-oxide and of isonicotinic acid N-oxide are more complex than those of the previous four compounds, but are similar to each other. 相似文献
6.
Claude CommandeurMalgorzata Commandeur Kathell BathanyBrice Kauffmann Andrew J.F. EdmundsPeter Maienfisch Léon Ghosez 《Tetrahedron》2011,67(51):9899-9908
This report describes a detailed study of the oxidation-Meisenheimer rearrangement of N-methyl-3-hydroxy-7-chloropyrroloindoline ethyl ester and the corresponding O-Boc and N-Boc derivatives. Experimental conditions were found, which allowed the selective Boc protection of either the tertiary alcohol substituent or the NH group of the aminal function. It was shown that both the parent compound and its O-Boc derivative yielded a mixture of oxazines and, in some cases, N-oxides upon treatment with m-CPBA. MS fragmentation (APCI) clearly differentiates formation of N-oxides and oxazines. The N-Boc derivatives exclusively yielded the N-oxides showing that the Meisenheimer rearrangement requires the presence of a high energy lone pair on the neighbouring nitrogen atom. Both the parent compound and the O-Boc derivative gave a mixture of rearranged products and N-oxide depending on the reaction conditions. 相似文献
7.
M. Bartoszek D. Salzwedel G. Stumm H.-J. Niclas 《Journal of mass spectrometry : JMS》1987,22(5):259-268
Quinoxaline N-oxides substituted at the ortho position to the NO group give characteristic [M – OH]+ fragments. With the di-N-oxides the peak intensities depend on the electron-withdrawing strength of the 2- and 3-substituents. Linear discriminant analysis was used to study the fragmentation of quinoxaline N-oxides as determined by the number of NO groups. Results of peak selection and discriminant analysis (Fisher quotients and discriminant vector coefficients) were interpreted with regard to the mass spectrometric decomposition of quinoxaline and quinoxaline N-oxide molecules. For the substituted quinoxaline TV-oxides, fragmentations involving molecular rearrangements like those observed for unsubstituted quinoxaline N-oxidles were also found. For these compounds, partial rearrangement to quinoxalinones is confirmed. 相似文献
8.
Seiji Yamaguchi Keiko Orito Noriko Shimizu Katsunori Taniguchi Hideo Saitoh Masahide Kurosaki Hajime Yokoyama Yoshiro Hirai Shunsaku Shiotani 《Journal of heterocyclic chemistry》1999,36(1):81-94
Furo[2,3-b:4,5-c‘]- 1a , -[3,2-b:4,5-c’]- 1b , -[2,3-c:4,5-c‘]- 1c and -[3,2-c:4,5-c’]dipyridine 1d were derived to the N-oxides 2a-d , N‘-oxides 2′b , 2′c or N,N’-dioxide 3b-d by N-oxidation with m-chloroperbenzoic acid. Chlorination of these N-oxides, N′-oxide and N,N′-dioxides with phosphorus oxychloride afforded compounds chlorinated at the α-position(s) to the ring nitrogen 4a-d , 4′c , 14b-d and 14′b . Acetoxylation of N-oxides 2a-d and 2′c with acetic anhydride gave the corresponding pyridone compounds 6a-d and 6′c in good yields, while the acetoxylation of N,N′-dioxides gave a complex mixture from which no compound could be isolated. Cyanation of 2a-d, 2′c and 3b-d with trimethylsilyl cyanide yielded the cyano compounds 7a-d , 7′c , cyano-N-oxides 15b-d and dicyano compounds 15′c and 15′d . Monocyano compounds 7a-d and 7′c were converted to the imino esters 8a-d and 8′c by treatment with sodium ethoxide. Imino esters were derived to the carboxylic esters 9a-d and 9′c , from which the corresponding alde hydes 10a-d and 10′c were obtained by reduction with diisobutylaluminum hydride. Dicyanide 15′c was converted to dialdehyde 19 by the treatment with sodium ethoxide, and the subsequent hydrolysis of the imino ester and reduction of the carboxylic ester with diisobutylaluminum hydride. 相似文献
9.
J. V. Frechina P. Palanca T. Picher V. Sanz J. A. Ramirez 《Journal of heterocyclic chemistry》1993,30(3):663-665
4-Substituted 1,3-oxathiolan-5-ones have been synthesized via the Pummerer rearrangement from the S-oxide of the parent molecule. The 4,5-dione is obtained in the presence of pyridine N-oxide. 相似文献
10.
V. A. Samsonov Yu. V. Gatilov V. A. Savel’ev S. S. Baranova 《Russian Journal of Organic Chemistry》2012,48(3):399-410
Reactions of 5-nitrospiro[benzimidazole-2,1′-cyclohexane] 1,3-dioxide with aliphatic amines and sodium hydroxide resulted
in removal of one N-oxide oxygen atom and formation of 4-alkylamino- or 4-hydroxy-substituted 5-nitrospiro[benzimidazole-2,1′-cyclohexane] 1-oxides,
respectively. The title compound reacted with ammonia and methylamine in the presence of MnO2 with conservation of both N-oxide moieties, and the products were 4-amino- and 4-methylamino-5-nitrospiro[benzimidazole-2,1′-cyclohexane] 1,3-dioxides.
The reactions with aromatic amines were accompanied by removal of both N-oxide oxygen atoms with formation of N-aryl-5-nitrospiro[benzimidazole-2,1′-cyclohexane]-4-amines. In the reactions of 5-nitrospiro-[benzimidazole-2,1′-cyclohexane]
1,3-dioxide with sodium azide and aromatic amine hydrochlorides nucleophilic replacement of the 5-nitro group by azido or
arylamino occurred, in the first case both N-oxide fragments being conserved. The reactions with aromatic amine hydrochlorides afforded N-aryl-5-nitrospiro[benzimidazole-2,1′-cyclohexan]-4-amine 1-oxides. Treatment of 5-nitrospiro[benzimidazole-2,1′-cyclohexane]
1,3-dioxide with sodium cyanide led to the formation of 5-oxo-3,5-dihydrospiro[benzimidazole-2,1′-cyclohexane]-4-carbonitrile
1-oxide. 相似文献
11.
Xiu-Sheng Miao Raymond E. March Chris D. Metcalfe 《International journal of mass spectrometry》2003,230(2-3):123
A mass spectrometric study of three N-oxides, quinoline N-oxide, and the synthetic antibiotics carbadox and olaquindox, was carried out with a hybrid quadrupole/time-of-flight (TOF) mass spectrometer coupled with electrospray (ES) and atmospheric pressure chemical ionization (APCI) sources. The full scan mass spectra of the N-oxides obtained with ES are similar to those obtained with APCI, and the characteristic fragment ions corresponding to [M+H−O]+√ were observed in the full scan mass spectrum of each N-oxide examined. The protonated molecule of each N-oxide was subjected to collision-induced dissociation (CID) and accurate mass measurements were made of each fragment ion so as to determine its elemental composition. Fragment ions generated at enhanced cone voltages upstream of the first mass-resolving element were subjected to CID so as to identify the direct product ion–precursor ion relationship. Plausible structures have been proposed for most of the fragment ions observed. Elimination of OH√ radicals generated from the N→O functional group is a characteristic fragmentation pathway of the N-oxides. The expulsion of radicals and small stable molecules is accompanied by formation and subsequent contraction of heterocyclic rings. 相似文献
12.
Ja-An Su Ernest Siew Ellis V. Brown Stanford L. Smith 《Magnetic resonance in chemistry : MRC》1978,11(11):565-574
Carbon-13 chemical shift assignments are reported for four chloroquinolines, six chloroisoquinolines, one dichloroquinoline, four dichloroisoquinolines, four methylchloroquinolines, two methylchloroisoquinolines, quinoline N-oxide, isoquinoline N-oxide, five methylquinoline N-oxides, two methylisoquinoline N-oxides and three chloroisoquinoline N-oxides. Chlorine substituent chemical shift (SCS) effects are reported for the alpha, ortho, meta, para and peri positions. Consistent patterns are observed for the para and peri positions, a vinylogous ortho pattern is reported and the additivity of these SCS effects is demonstrated. Alpha SCS effects vary widely from 1.1 ppm upfield in 1-chloroisoquinoline to 6.7 ppm downfield in 4-chloroquinoline. These results, together with those in the literature, permit the definition of steric and nitrogen lone-pair contributions which modify the ‘normal’ chlorine SCS effect, and these modifying contributions are shown to be roughly additive. Large (6–16 ppm) upfield shifts are observed for the carbons ortho and para to the N-oxide group. The individual magnitudes of these shifts and their sum are constant and the effects are additive in substituted systems. A 9.5 ppm upfield shift is also observed for C-8 in quinoline N-oxides which is attributed to a space–charge interaction. Substituent chemical shift (SCS) effects for the chloro and methyl groups and the chemical shifts of the methyl carbons are essentially the same in the N-oxides as in the parent heterocycles and are additive, except for those molecules where the substituent is adjacent to the N-oxide moiety, in which cases substantial interactions are observed. 相似文献
13.
Ya. V. Veremeichik P. V. Merabov A. V. Chuiko O. A. Lodochnikova V. V. Plemenkov 《Russian Journal of Organic Chemistry》2013,49(11):1605-1609
From substituted N-sulfinylanilines acting as dienes in the Diels-Alder reaction with norbornadiene S-oxides of benzo-ortho-thiazines were obtained, which were oxidized into the corresponding S,S-dioxides belonging to the class of hybrid thiazinesulfonamide compounds. 相似文献
14.
Thomas Blumenthal Richard G. Gillis Quentin N. Porter Li Li Yeoh 《Journal of mass spectrometry : JMS》1991,26(4):247-249
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. 相似文献
15.
Reactions of pyridine N-oxides, pyrazine di-N-oxides, and their benzologues with formamide are described. Carbamoylation mainly occurred at aromatic ring with loss of the N-oxide oxygen atom, however, 2,4,6-trimethylpyridine 1-oxide gave 2- and 4-pyrimidinyl derivatives. 相似文献
16.
Giulia Caron Giuseppe Ermondi Donatella Boschi Pierre-Alain Carrupt Roberta Fruttero Bernard Testa Alberto Gasco 《Helvetica chimica acta》1999,82(10):1630-1639
Homologous N,N-dimethyl-phenylalkylamine oxides and N,N-dimethyl-diphenylalkylamine oxides were prepared. Their basicity and lipophilicity (octan-1-ol/H2O) were compared to those of the parent amines. In contrast to the amines, the basicity of all N,N-dimethyl-arylalkylamine oxides showed very limited pKa variations (range 4.65 – 5.01) with increasing chain length and number of Ph groups. The N-oxides in their neutral form had a log PN value lower by 2.77±0.34 (n=9) units than that of the parent amine. The log PC of the cationic N,N-dimethyl-diphenylalkylamines was lower than that of their neutral form, with a decrement diff(log PN−C) that increased from 3.25 to 4.21 in the homologous series. Unexpectedly, the decrement diff(log PN−C) for the N-oxides was much smaller than for the tertiary amines, being 0.23 for the aliphatic N,N-dimethyl-pentylamine oxide, 0.47±0.13 for the phenylalkylamine oxides, and 0.80±0.07 for the diphenylalkylamine oxides. In fact, the protonated N-oxides had log PC values that were quite comparable to those of the protonated parent amines. Because of the differences in basicity, the difference in distribution coefficients at physiological pH (log D7.4) between a tertiary arylalkylamine and its N-oxide was 0.82±0.66 (n=9). The pharmacokinetic implication is that N-oxygenation may have a smaller effect on the urinary excretion of tertiary amines than usually assumed. 相似文献
17.
Charles W. Koch Richard M. Milberg Robert J. Katt J. Hodge Markgraf P. M. Wege 《Journal of heterocyclic chemistry》1974,11(4):475-479
High resolution mass spectra of compounds 1—8 were investigated. For the quinolines (1–3) the absence of major peaks other than M+ and (M-1)+ reflects the stability of those systems. The N-oxides (4–6) all exhibit major peaks at M+, (M-16)+, and (M-17)+. In addition, 4 shows prominent fragmentations reflecting loss of hydrogen and carbon monoxide. The pathways are related to the geometries of the N-oxides; deuterated compounds (7–8) aided these assignments. 相似文献
18.
Yoshihisa Kurasawa Atsushi Takada Ho Sik Kim 《Journal of heterocyclic chemistry》1995,32(4):1085-1114
This review describes the 1,3-dipolar cycloaddition reaction, deoxygenation, deoxygenative transformation, ring transformation and photochemical reaction of quinoxaline N-oxides and N,N′-dioxides. 相似文献
19.
Wang C Li Y Gao J He Y Xiong A Yang L Cheng X Ma Y Wang Z 《Analytical and bioanalytical chemistry》2011,401(1):275-287
Pyrrolizidine alkaloids (PAs) are considered to be one of the most hepatotoxic groups of compounds of plant origin and are
present in about 3% of the world’s flowering plants. Most PAs represent a considerable health hazard to both livestock and
humans through the consumption of plants and PA-contaminated products such as milk, honey, herbal teas, and medicines. This
study determined the differences in the in vivo pharmacokinetic behavior of senecionine (SEN), adonifoline (ADO), and their
main metabolites in rats after intravenous administration and oral administration by ultraperformance liquid chromatography/electrospray
ionization mass spectrometry. Upon intravenous administration and oral administration of SEN and ADO, significant differences
in pharmacokinetics were observed, with the SEN and ADO being absorbed fast with lower bioavailability and being quickly metabolized
to PA N-oxides and hydroxylation products of PAs or their N-oxides. It could be seen that the plasma concentration ratio of senecionine N-oxide (SEN-NO) to SEN (C
SEN-NO/C
SEN) was significantly larger than that for adonifoline N-oxide (ADO-NO) and ADO (C
ADO-NO/C
ADO) (P < 0.001) for both dosing routes in rats. The high N-oxygenation activity and extensive toxicity of SEN, compared with ADO, in rats raised the question of whether or not the
higher metabolic rate of SEN in rats in vivo was related to its potent toxicity. The toxicity of SEN-NO and ADO-NO needs to
be evaluated further and compared in vitro/in vivo. This study was most helpful for interpreting the metabolism of metabolic
bioactivation and detoxication, and toxicity differences among SEN, ADO and other PAs. 相似文献
20.
The noise-decoupled nitrogen-15 NMR spectra of ten pyridine N-oxides and two quinoline N-oxides have been obtained at the natural-abundance level by high-resolution NMR spectroscopy. Substituents at the 4-ring position of pyridine N-oxide, capable of resonance interaction with the N-O moiety, give fairly large shifts in the expected directions. Spectra taken in dimethyl sulfoxide solution give 5–20 ppm and 33–55 ppm downfield shifts with respect to the solutions of the same substances in 2,2,2-trifluoroethanol and trifluoroacetic acid. Solvent influences are discussed in terms of hydrogen bonding and protonation of the N-oxide oxygen. Carbon-13 chemical shifts and one-bond carbon-hydrogen coupling constants of some substituted pyridine N-oxides are reported and discussed. 相似文献