PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Nitro Compounds”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25Linked to original sources
PubMed2005

Supramolecular oxidation of anilines using hydrogen peroxide as stoichiometric oxidant.

6A,6D-Di-O-(propan-2-on-1,3-diyl) alpha-cyclodextrin-6A,6D-dicarboxylate (2alpha) and 6A,6D-di-O-(propan-2-on-1,3-diyl) beta-cyclodextrin-6A,6D-dicarboxylate (2beta) were found to catalyze the oxidation of aromatic amines in the presence of hydrogen peroxide. The products were the corresponding nitro compounds or in some cases azo-, azoxy-, or other dimerization products. The catalysis was found to follow enzyme kinetics giving a rate increase (kcat/kuncat) of up to 1100 in the best case.

Journal Article↗
PubMed1977

Studies on anticoccidial agents. 11. Synthesis and anticoccidial activity of nitropyridinecarboxamides and derivatives.

Of the nine nitropyridinecarboxamides, which are isomers of 5-nitronicotinamide, a potent anticoccidial agent, 2-nitropyridine-3, -4, -5-, or 6-carboxamides and 3-nitropyridine-4- or 6-carboxamides were prepared from the corresponding acids via the esters of the acid chlorides. 3-Nitropyridine-2-carboxamide was obtained from 2-methyl-3-nitropyridine by oxidation with SeO2, oximation, dehydration with Ac2O, and hydrolysis with H2SO4. 4-Nitropyridine-2-carboxamide was prepared from 2-cyano-4-nitropyridine by hydrolysis, and the 3-carboxamide analogue was obtained from 4-amino-3-cyanopyridine by oxidation with H2O2 and fuming H2SO4. Of these compounds 2-nitro- and 3-nitro- but not 4-nitropyridinecarboxamides were found to be active against Eimeria tenella. N-Substituted analogues of 2-nitro- and 3-nitropyridine carboxamides were also prepared in a conventional manner and optimal anticoccidial activity was attained with 2-nitroisonicotinamide and its N-alkanoyl, N-aromatic, and N-heterocyclic acyl derivatives.

Animals↗
PubMed2000

An efficient preparation of vinamidinium hexafluorophosphate salts.

Substituted acetic acids or acetyl chlorides react with phosphorus oxychloride in DMF to yield the vinamidinium salts 3a-j in moderate to excellent recrystallized yields (28-90%). The cations are conveniently isolated as their hexafluorophosphate salts, which are easily handled nonhygroscopic solids. The nitro compound 3l is prepared in 91% yield by nitration of the parent vinamidinium 3k. The X-ray crystal structure is reported for the 2-phenyl isomer 3e and displays minimal overlap of the two pi-systems.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

Bone collagen cross-links: a convergent synthesis of (+)-deoxypyrrololine.

A convergent total synthesis of (+)-deoxypyrrololine (Dpl, 4), a putative cross-link of bone collagen, is described starting from a commercially available L-glutamic acid derivative, (4S)-5-(tert-butoxy)-4-[(tert-butoxycarbonyl)amino]-5- oxopentanoic acid (16). Condensation of aldehyde (S)-(-)-17 with nitro compound (S)-(-)-27, both of which were prepared from a common precursor (S)-16, gave the alpha-hydroxynitro compound 28, which upon acetylation afforded alpha-acetoxynitro compound 14 in good yield. Subsequent condensation and cyclization of alpha-acetoxynitro compound 14 with benzyl isocyanoacetate (15) in the presence of DBU in THF gave the key pyrrole intermediate (S,S)-(-)-12 in 57% yield. N-Alkylation of pyrrole (S,S)-(-)-12 with iodide (S)-(-)-13 using t-BuOK in THF afforded the 2-benzyloxycarbonyl-1,3,4-substituted pyrrole derivative (-)-29 in 42% yield. Removal of the protective groups in (-)-29 followed by hydrogenolysis and decarboxylation afforded the cross-link (+)-Dpl (4) in good overall yield. The synthesis of an analogue (S)-(+)-24 and formation of a novel tetrahydroindole derivative (-)-31 are also described.

Amino Acids↗
PubMed2002

Diethyl chlorophosphite: a versatile reagent.

Diethyl chlorophosphite (DECP) was previously described as a reducing agent for nitro compounds to the corresponding amines (Fischer, B.; Sheihet, L. J. Org. Chem. 1998, 63, 393). Here, the utility of this reagent was extended to chemical conversions of other oxygenated functional groups. In this paper we report on the scope of the reaction of DECP with N-oxides, epoxides, sulfones, sulfoxides, hydroxylamines, ketoximes, and aldoximes. The chemoselectivity of DECP is described, and conditions for a stepwise multiple conversion of functional groups on the same molecule with this reagent are provided.

Journal Article↗
PubMed2002

Chelation-controlled reduction: stereoselective formation of syn-1,3-diols and synthesis of compactin and mevinolin lactone.

Chelation-controlled reduction of chiral beta-alkoxy ketones containing a competing beta'-oxygen functionality has been investigated. Various syn-1,3-diols were prepared conveniently by reduction of beta-alkoxy ketones with LiI/LiAlH(4) (syn:anti selectivity up to >99:1). The corresponding beta-alkoxy ketones were derived from nitro-aldol reactions of chiral alkoxy aldehydes with a series of nitro compounds. This methodology is utilized in a short and efficient synthesis of the delta-lactone moiety of the HMG-CoA reductase inhibitors compactin and mevinolin.

Alcohols↗
PubMed2003

Phosphoramidites are efficient, green organocatalysts for the Michael reaction. Mechanistic insights into the phosphorus-catalyzed Michael reaction of alkynones and implications for asymmetric catalysis.

Hexamethylphosphorous triamide (HMPT) and other phosphoramidites and phosphites have been found to be efficient catalysts for the Michael reaction of alkenones and alkynones with malonates, alpha-cyano esters, beta-keto esters, and nitro compounds. The relatively nontoxic, easily hydrolyzed HMPT catalyzes the Michael reaction within seconds at room temperature in the absence of a solvent, and the reaction is worked up simply by removing the catalyst in vacuo. The Michael reactions of alkynones, unlike those of alkenones, are shown to be irreversible. The implications for asymmetric catalysis are discussed.

Alkenes↗
PubMed2004

New synthetic equivalent of nitromalonaldehyde treatable in organic media.

beta-Nitroenamines having a formyl group at the beta-position behave as the synthetic equivalent of unstable nitromalonaldehyde, which is a useful synthon for syntheses of versatile nitro compounds. High solubility of the nitroenamines into general organic solvents enables us to conduct reactions in the organic media accompanied by easy experimental manipulations and considerable safety. When nitroenamines are treated with 1,2-bifunctional nucleophiles such as hydrazines, hydroxylamine and glycine ester, nitrated pyrazoles, isoxazole and pyrrole-2-carboxylate were readily prepared. This methodology was also applicable to guanidines and 1,2-diamines, leading to pyrimidines and 1,4-diazepines, respectively.

Journal Article↗
PubMed2005

Study of photoinduced N-hydroxy-arylnitroxide radicals (ArNO*OH) by time-resolved EPR.

The photoreduction of aromatic nitro compounds by alcohols is a well-known reaction; however, the first stages of its mechanism remain controversial. This study aims at characterizing the "primary" radicalar transients involved in this reaction by EPR spectroscopy. Laser flash photolysis (lambda = 266 nm) of nitrobenzene, 5-nitrouracil, p-nitroacetophenone, o-propylnitrobenzene, and 2-nitroresorcinol in ethylene glycol was followed by time-resolved EPR spectroscopy. In all reported TR-EPR spectra, except those obtained from the photolysis of 2-nitroresorcinol, the key intermediate N-hydroxy-arylnitroxide radicals (ArNO*OH, 1-4) could be identified unambiguously. In 2-nitroresorcinol, the radical anion (ArNO*O(-), 5) and a sigma iminoxy radical (6) were observed, and a third radical (7) remains unidentified. These observations indicate that two radicalar mechanisms (by H* transfer and by electron transfer) are competing in the photoreduction mechanism. The attribution of the EPR spectra was helped by DFT calculations of the hyperfine coupling constants (hcc's).

Electron Spin Resonance Spectroscopy↗
PubMed2006

Uptake of HNO3 on hexane and aviation kerosene soots.

The uptake of HNO(3) on aviation kerosene (TC-1) soot was measured as a function of temperature (253-295 K) and the partial pressure of HNO(3), and the uptake of HNO(3) on hexane soot was studied at 295 K and over a limited partial pressure of HNO(3). The HNO(3) uptake was mostly reversible and did not release measurable amounts of gas-phase products such as HONO, NO(3), NO(2) or N(2)O(5). The heat of adsorption of HNO(3) on soot was dependent on the surface coverage. The isosteric heats of adsorption, Delta(0)H(isosteric), were determined as a function of coverage. Delta(0)H(isosteric) values were in the range -16 to -13 kcal mol(-1). The heats of adsorption decrease with increasing coverage. The adsorption data were fit to Freundlich and to Langmuir-Freundlich isotherms. The heterogeneity parameter values were close to 0.5, which suggested that a HNO(3) molecule can occupy two sites on the surface with or without being dissociated and that the soot surface could be nonuniform. Surface FTIR studies on the interaction of soot with HNO(3) did not reveal formation of any minor product such as organic nitrate or nitro compound on the soot surface. Using our measured coverage, we calculate that the partitioning of gas-phase nitric acid to black carbon aerosol is not a significant loss process of HNO(3) in the atmosphere.

Aviation↗
PubMed2006

Double-layer effects and distance dependence of electron transfer in reduction of nitro aromatic radical anions.

The first example of the effect of an electric double layer on the reduction of electrochemically generated radical species is reported. The anion radical of methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate (pesticide bifenox) is electrochemically reduced in acetonitrile to a phenylhydroxylamine derivative in a process involving three electrons. This heterogeneous reaction is strongly influenced by the concentration and nature of the cation of the indifferent electrolyte. Depending on the type of tetraalkylammonium cation, the redox potential changes by 0.45 V. The kinetic parameters were obtained for five tetraalkylammonium hexafluorophosphate salts. The Frumkin correction, which assumes that the outer Helmholtz plane coincides with the reaction site, was applied to kinetic data of the radical anion reduction. The correction of the apparent rate accounted for the observed effect only in the case of tetramethylammonium salt. The presence of higher tetraalkylammonium homologues causes deviations from the predicted dependence of the electron-transfer rate on the phi2 potential of the outer Helmholtz plane. Hence, the nature of the cation of the electrolyte exerts a further effect extending beyond the electrostatic repulsion only. The corrected rate of electron transfer decreases exponentially with increasing size of the alkyl chain of the indifferent electrolyte cation in the order methyl > ethyl > propyl > butyl > hexyl. The rate decay is characterized by an exponent beta = 0.83. This confirms that the reaction plane for the reduction of the bifenox radical anion is different for each electrolyte. Due to this fact the Frumkin correction cannot fully account for the observed dependence of the heterogeneous rate on the solution composition. The observed effect is not specific to the bifenox radical. A similar influence of the concentration and nature of the cation of the indifferent electrolyte was observed for other nitro compounds, namely, nitrobenzene, nitrobenzoate, and nitrofen.

Journal Article↗
PubMed2001

A new polymer-anchored chiral catalyst for asymmetric Michael addition reactions.

[figure: see text] Monomer (R,R)-3-aza-3-(p-vinylbenzyl)-1,5-diphenyl-1,5-dihydroxypentane (2) when polymerized with styrene and divinylbenzene affords polymers, onto which lithium and aluminum are incorporated via reaction with lithium aluminum hydride. The resulting insoluble polymers containing chiral lithium and aluminum active centers are quite effective for asymmetric Michael addition of nitro compounds, thiols, and amines. The optimized reaction conditions yield Michael adducts in good yield with high enantiomeric excesses.

Journal Article↗
PubMed2001

Catalytic direct asymmetric Michael reactions: taming naked aldehyde donors.

[reaction--see text] Direct catalytic enantio- and diastereoselective Michael addition reactions of unmodified aldehydes to nitro olefins using (S)-2-(morpholinomethyl)pyrrolidine as a catalyst are described. The reactions proceed in good yield (up to 96%) in a highly syn-selective manner (up to 98:2) with enantioselectivities approaching 80%. The resulting gamma-formyl nitro compounds are readily converted to chiral, nonracemic 3,4-disubstituted pyrrolidines.

Aldehydes↗
PubMed2002

Conversion of N-aromatic amides to O-aromatic esters.

[reaction: see text] N-Aromatic secondary amides can be transformed into O-aromatic esters in high yield via N-nitrosamide intermediates. The amides can be generated in situ from the corresponding aromatic amines or nitro compounds, and phenols can easily be made from the esters. The reaction can be modified by addition of methyl methacrylate or toluene at 0 degrees C to give polymerization or deamination, respectively. The rearrangement mechanism may involve radical formation and recombination.

Journal Article↗
PubMed2003

New approach for the synthesis of isoxazoline-N-oxides.

A strategy for the synthesis of isoxazoline-N-oxides (cyclic five-membered nitronates) from primary nitro compounds and olefins is described. The key step of the process involves 1,3-dipolar cycloaddition of corresponding 1-bromosilyl nitronates with alkenes. [reaction: see text]

Journal Article↗