3-imidazoline 3-oxide Research Articles

Synthesis and characterization of some novel 4-furyl substituted 3-imidazoline 3-oxides

Novel 4-furyl substituted 3-imidazoline 3-oxides were synthesized by the reaction of 2-bromo-1- (2-furanyl)ethanone oxime with aromatic amines and aldehydes, including formaldehyde, using one pot procedures involving the reactions of in situ formed α-amino oximes with aldehydes and also by one pot procedures involving the reactions of in situ formed imines with α-halo oximes.

α-Organoelement Nitrones: Synthesis, Properties, and IR and 13C NMR Spectral and X-ray Structural Characterization

α-Organoelement-substituted nitrones have been synthesized for the first time through the reaction of the α-lithiated cyclic aldonitrones of 3-imidazoline 3-oxide, pyrroline 1-oxide, 2H-imidazole 1-oxide, and 3,4-dihydroisoquinoline 2-oxide series with electrophilic reagents such as HgCl2, (CH3)3SiCl, (C2H5)3GeCl, (n-C4H9)3SnBr, Ph2P(O)Cl, Ph2PCl, PhSSPh, PhSeSePh, TsCl, and TsF. Aldonitrones of the 3-imidazoline 3-oxide and pyrroline 1-oxide series were shown to readily afford the products of the lithiation−electrophilic substitution reaction. In contrast, aldonitrones of the 2H-imidazole 1-oxide and 3,4-dihydroisoquinoline 2-oxide series react smoothly only with halogen-free electrophiles. It was found that an aldonitrone group could be lithiated and selectively reacted with electrophiles even when kinetically more acidic methylene and amino groups are present in the molecule. Characteristic features of IR and 13C NMR spectra of the compounds synthesized are discussed. Selected α-organoelement nitrones are characterized by an X-ray diffraction study.

Dipolar Cycloadditions of Imidazoline 3‐Oxides with N‐Arylmaleimides. Synthesis and Diethylamine Induced Ring‐Opening of exo and endo Hexahydro‐7‐oxa‐2,5,6a‐triaza‐cyclopenta[a]pentalene‐1,3‐diones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Dipolar cycloadditions of imidazoline 3-oxides with N-arylmaleimides. Synthesis and diethylamine induced ring-opening of exo and endo hexahydro-7-oxa-2,5,6a-triaza-cyclopenta[ a]pentalene-1,3-diones

1,4-Diarylimidazoline 3-oxides react with N-arylmaleimides in benzene to give predominantly the corresponding endo adducts. Chiral imidazoline 3-oxides react diastereospecifically (cis configuration of the tetrahydroimidazo ring) and diastereoselectively to give cis– endo adducts. The effects of substituents on the aromatic ring of the maleimide was investigated. The presence of electron-withdrawing or releasing groups have minor effect on the total yields but more pronounced is the effect on the ratio of exo and endo diastereomers. The adducts undergo an interesting and unprecedented ring-opening in the presence of secondary amines to give deoxygenated 3-imidazoline 3-oxides instead of the expected double cis elimination products. Tertiary amines did not induce any reaction.

NMR Spectra of Cyclic Nitrones. 7. The Influence of Substituents and a Hydrogen Bond on 14N and 17O Chemical Shifts in Derivatives of 3-Imidoazoline 3-Oxide

Derivatives of 3-imidazoline 3-oxide have been studied by 14N and 17O NMR methods. Regularities of the influence of substituents and of a hydrogen bond on chemical shifts have been made apparent. The range of changes of the chemical shifts of the nitrogen and oxygen nuclei of the nitrone group has been determined. Both in the 17O and in the 14N NMR spectra the signals of the amino derivatives are the highest field signals for the nitrone group, and the lowest field signals are the signals of the cyano derivatives in the series of derivatives investigated. Depending on the substituent (from amino to cyano group) the 17O chemical shifts varied over a range ∼155 ppm, but the interval of change of the 14N chemical shifts for the same substituents was ∼110 ppm.

ChemInform Abstract: Dipole-Stabilized Carbanions in Series of Cyclic Aldonitrones. Part 2. Reactions of the Metalated Aldonitrones - Derivatives of 3-Imidazoline 3-Oxide and 2H-Imidazole 1-Oxide with Aldehydes and Ketones.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The first examples of di- and cis triaryl-3a,4,5,6-tetrahydroimidazo[1,5- b]isoxazoles and their ring-opening reactions

The Δ 3-imidazoline 3-oxides 1 undergo diastereoselective cycloaddition with dimethyl acetylenedicarboxylate 2 to give 3a,4,5,6-tetrahydroimidazo[1,5- b ]isoxazoles 3. Thermal and base induced ring-opening reactions of compounds 3 were demonstrated.

Dipole-Stabilized Carbanions in Series of Cyclic Aldonitrones. Part 2: Reactions of the Metalated Aldonitrones—Derivatives of 3-Imidazoline 3-Oxide and 2 H-Imidazole 1-Oxide with Aldehydes and Ketones

Metalated aldonitrones of 3-imidazoline 3-oxide and 2 H-imidazole 1-oxide series react with a wide variety of aldehydes and ketones leading to the unknown α-hydroxymethyl nitrones. Reaction of 2,2-dimethyl-4-phenyl-2 H-imidazole 1-oxide with allylacetone spontaneously lead to tricyclic 3,3,8-trimethyl-1-phenyl-5a,6,7,8-tetrahydro-3 H,5 H-4-oxa-2,3a-diaza-cyclopenta[ c]pentalen-8-ol. The hydroxy group of (1,2,2,5,5-pentamethyl-2,5-dihydro-1H-imidazol-3-oxide-4-yl)phenylmethanol is substituted with piperidine to give, after further transformations, (1,2,2,5,5-pentamethyl-2,5-dihydro-1 H-imidazol-4-yl)phenylmethanone.

Regio and diastereoselective addition of imidazoline 3-oxides to aryl isocyanates

Δ 3-Imidazoline 3-oxides 1 underwent regio and diastereoselective cycloaddition with aryl isocyanates 2 to give 5,6,7,7a-tetrahydroimidazo[1,5- b ][1,2,4]oxadiazol-2(1 H )-ones 3 in excellent yields. Thermally and chemically induced retro cycloaddition of compounds 3 was demonstrated.

Regio and diastereoselective addition of imidazoline 3-oxides to aryl isocyanates

Δ 3-Imidazoline 3-oxides 1 underwent regio and diastereoselective cycloaddition with aryl isocyanates 2 to give 5,6,7,7a-tetrahydroimidazo[1,5- b ][1.2.4]oxadiazol-2(1 H )-ones 3 in excellent yields. Thermally and chemically induced retro cycloaddition of compounds 3 was demonstrated.

Synthesis and properties ofN-[1-hydroxyimino-2-methyl-1-(2-pyridyl)prop-2-yl]hydroxylamine and heterocyclic derivatives based on it

N-[1-Hydroxyimino-2-methyl-1-(2-pyridyl)prop-2-yl]hydroxylamine, a new representative of the series of α-hydroxylamino oximes, was synthesized. Based on this compounds, 3-imidazoline 3-oxide and 2-imidazoline 3-oxide derivatives, were obtained, and some of their chemical properties were investigated.

Synthesis and oxidation of 1-hydroxy-3(2)-imidazoline-derived enaminones

Interaction of 1-hydroxy-3-imidazoline and 3-imidazoline 3-oxide derivatives with esters in the presence of LDA gives enaminones, derivatives of imidazolidine. Oxidation of these compounds with MnO2 leads to4H-imidazoleN-oxides, oxidative dirnerization products, or stable nitroxyl radicals, depending on the structure of the initial compound.

Derivatives of Dihydropyrazine-1,4-Dioxide, 3-Imidazoline 3-Oxide, and α-Phenyl Nitrones with Functional Groups as New Spin Traps in Solution and in the Gas Phase

The title compounds, acyclic phenyl nitrones with functional groups, cyclic dinitrones with conjugated or isolated double bonds, and imidazoline nitrones are studied as spin traps (ST) for short-lived free radicals (R) generated photochemically in solution and in the gas phase. New STs are efficient in trapping OH, hydroxyalkyl, or HO2 radicals. EPR spectra of the spin adducts (SA) of studied dinitrones are triplets of doublets characteristic of the nitroxides with one radical center. Imidazoline ST with amino nitrogen exhibits pH-dependent hyperfine splittings of its SAs. Some spin traps were shown to be efficient in detecting R in the atmospheric experiments.

Regio- and stereoselectivity of 1,3-dipolar cycloaddition of cyclic aldonitrones of the 3-imidazoline 3-oxide series to monosubstituted alkenes

Regio- and stereoselectivity of 1,3-dipolar cycloaddition of cyclic aldonitrones of the 3-imidazoline 3-oxide series mainly depends on the type of the substituent in the dipolarophile. The configuration of the main cycloadduct has been determined, and a method has been suggested to establish the stereochemistry of the cycloaddition products by1H NMR spectroscopy. An increase in electron-acceptor properties of the substituent in the alkene molecule results in a decrease in the regio- and stereoselectivity of the cycloaddition.

Synthesis and properties of heterocyclic ?-nitronitrone: 1,2,2,5,5-pentamethyl-4-nitromethyl-3-imidazoline 3-oxide

The reaction of methyl nitrone, a derivative of 3-imidazoline 3-oxide, with methyl nitrate in the presence of PhLi results in β-nitronitrone. The tnteraction of the latter with electrophiles involves, as a rule, the methylene group. Nitrile oxide, which is an 3-imidazoline 3-oxide derivative, has been generated by thermolysis ofgem-nitrooxime. This easily dimerizes to furoxan or undergoes regioselective 1,3-dipolar cycloaddition with alkenes.

Reaction of sterically hindered 1-hydroxy-3-imidazoline 3-oxides with phenyllithium

The reaction of 3-imidazoline 3-oxide derivatives with phenyllithium followed by oxidation affords nitroxyl radicals of the 2-imidazoline or 2-imidazoline 3-oxide series depending on the nature of the substituent in position 2 of the heterocycle.

Electrochemical oxidation of 3-imidazoline 3-oxides

Cyclic voltammetry was used to study the electrochemical oxidation of substituted 3-imidazoline 3-oxides. It was determined that the oxidation potentials (Ep/2) of the compounds depend on the nature of the substituents in the 1 and 4 positions of the ring. A correlation analysis ofEp/2 of the the compounds and σ I and σ R of the substituent constants in the 4 position of the ring was carried out. The obtained results show that oxidation of 3-imidazoline 3-oxides can occur at the nitrone or amine fragment, depending on the nature of the substituent in the 1 position of the ring.

NMR spectra of cyclic nitrones. 5. 13C NMR spectra of the potential tautomeric systems of amino-, hydroxy-, and mercaptonitrones in the series of 3-imidazoline 3-oxide

The position of the tautomeric equilibrium in amino-, hydroxy, and mercaptonitrones was determined by the 13C NMR method for the case of the derivatives of 3-imidazoline-3-oxide. It was shown that the tautomeric equilibrium in the OH and SH derivatives is shifted toward the oxo and thioxo forms (∼95%). The chemical shifts of the carbon atoms of the nitrone group in the α-N-, α-O-, and α-S-substituted nitrones lie in the region of 137–150 ppm.

Oxidative alkoxylation of 4H-imidazole N-oxides as a new method of synthesis of stable nitroxyl radicals of the 2- and 3-imidazoline series with alkoxy groups at the ?-carbon atom of the radical center

1. Oxidation of 5-R1-2R2-4H-imidazole 1,3-dioxides in methanol with lead dioxide leads to the formation of stable nitroxyl and nitronylnitroxyl radicals with methoxy groups at the α-carbon atom of the radical center. The ratio between these radicals is determined by the electronic character of the substituents at the 2- and 5-positions of the heterocyclic ring. 2. Oxidation of 4H-imidazole 1-oxides and 4H-imidazole 3-oxides in methanol with lead dioxide leads to the formation of iminonitroxyl radicals. 3. Oxidation of 2-unsubstituted 4H-imidazole 1,3-dioxides and 4H-imidazole 3-oxides in alcohols by lead or manganese dioxides leads to 2,2-dialkoxy-substituted stable nitroxyl radicals, which are derivatives of 3-imidazoline 3-oxide and 3-imidazoline.

Vibrational spectra, structures, and conformations of conjugated azomethines ? 3-imidazoline derivatives

The possibility of the use of the ratios of the intensities of the v C=N bands in the Raman spectra of the compounds to establish the conformations of the conjugated C=N bonds was demonstrated in the case of conjugated azomethines — derivatives of 2,2,5,5-tetramethyl-3-imidazoline and — 3-imidazoline 3-oxide.