3-imidazoline 3-oxide Research Articles

The NMR spectra of cyclic nitrones. 3. Effect of protonation and a hydrogen bond on the chemical shifts in the13c NMR spectra of derivatives of 3-imidazoline 3-oxide

The effect of solvents on the13C NMR spectra of the cyclic nitrones of 3-imidazoline 3-oxide derivatives was studied. It was shown that in solvents capable of forming hydrogen bonds with the N-oxide group the signal for the nitrone carbon atom is shifted downfield by 1.5–2.5 ppm for solutions in chloroform and 5–9 ppm for solutions in methanol. The size of the shift depends on the substituent at position 1 of the imidazoline ring and decreases with increase in its accepting character. Analogous effects are observed during the formation of an intramolecular hydrogen bond with the oxygen atom of the nitrone group. During protonation of the nitrone group the downfield shift of the signal for the nitrone carbon atom amounts to 30–39 ppm.

ChemInform Abstract: New Derivatives of Imidazoline‐3‐oxide and Thiazoline with 2,6‐Dialkylphenol Fragments.

AbstractDie aus 2,6‐Dialkylphenolen (I) durch Umsetzung mit Methylvinylketon (II) hergestellten 4‐Arylbutanone (III) cyclisieren mit Amino‐oximen (IV) zu Imidazolin‐oxiden (V).

New derivatives of imidazoline 3-oxide and thiazoline with 2,6-dialkylphenol fragments

(2,6-Dialkyl-4-hydroxyphenyl)-2-butanones and aminooxides were used to obtain the corresponding 3-imidazoline 3-oxides. Nitrosylation of 3-imidazoline 3-oxide containing a phenol substituent proceeds either at the imidazoline ring amino group or at the phenol fragment. Intermolecular cyclization of (2,6-di-tert-butyl-4-hydroxyphenyl)-2-butanone with sulfur and ammonia gave a 3-thiazoline as two diastereomers.

Influence of nitroxyl radical center on keto-enol equilibrium of ?-keto-esters of 3-imidazoline derivatives

We used the keto-enol tautomerism of 4-carbomethoxyacetyl-3-imidazolines and 4-carbomethoxyacetyl-3-imidazoline 3-oxides and showed that in contrast to the radicals in the 3-imidazoline series, in the radicals of 3-imidazoline 3-oxide series, the spin effect of the radical center on the position of the tautomeric equilibrium is observed.

13C NMR spectra of cyclic nitrones. 2. 1- and 4-substituted 2,2,5,5-tetramethyl-3-imidazoline 3-oxides

The chemical shift of the carbon atom of the nitrone group in the 13C NMR spectra of 3-imidazoline 3-oxides lies in the region of 117–152 ppm and depends on the electronic effect of the substituants at positions 1, 4, and 5 of the heterocycle. Increase in the electron-withdrawing character of the substituent at these positions leads to an upfield shift of the signal for the nitrone carbon atom, and this corresponds to the increase in electron density on it.

Influence of radical center on oxidative properties of nitron group in reaction of nitroxyl radicals of 3-imidazoline 3-oxide withhydrazine

1. The influence of the radical center on the reactivity of the functional group in derivatives of 3-imidazoline 3-oxide not bound directly to it has been discovered. 2. In the reaction of nitroxyl radicals of a series of 3-imidazoline 3-oxides with hydrazine, two parallel processes take place: Reduction of the radical center to a hydroxylamino group and reduction of the nitron group to an amino group. 3. The desoxygenation process of the nitron group by hydrazine in alcohol at 20°C proceeds in the case of paramagnetic derivatives of 3-imidazoline 3-oxide only.

Recycltzation of the imidazoline ring in nitroxyl radical derivatives of 3-imidazoline following oxidation by halogens and nitrous acid

1. Nitroxyl radicals in 3-imidazoline 3-oxide are not oxidized by halogens, whereas nitroxyl radicals in 3-imidazoline react with chlorine, bromine, and nitrous acid with fission of the imidazoline ring. 2. 4-Carboxy-3-imidazoline-1-oxyls on treatment with bromine and nitrous acid undergo recyclization to 3-oxazolin-5-ones. 3. Bromine treatment of 4-formyl- and 4-acetyl-3-imidazolin-1-oxyl oximes results in recyclization to 2H-imidazole 1-oxides.

Synthesis and some reactions of sterically hindered 3-imidazoline 3-oxides

Sterically hindered 3-imidazoline 3-oxides were obtained by condensation of β-amino oximes with ketones. It is shown that the reaction of these compounds with electrophilic agents takes place at both the nitrone grouping and the amino group. The oxidation of the products makes it possible to obtain stable nitroxyl radicals.

ChemInform Abstract: SYNTHESIS OF STERICALLY HINDERED 1‐HYDROXY‐2‐ACETYL‐3‐IMIDAZOLINE 3‐OXIDES AND STABLE NITROXYL RADICALS BASED ON THEM

AbstractWerden die Hydroxylamine (I) mit Diacetyl (II) umgesetzt, so werden Imidazolin‐oxide (III) erhalten.

Preparation and covalent hydration of 4H-imidazole derivatives

2,4,4-Trimethyl-5-phenyl-4H-imidazole, 4H-imidazole 3-oxide, and 4H-imidazole 1,3-dioxide were synthesized from 1-hydroxy-2,5,5-trimethyl-4-phenyl-3-imidazoline and 3-imidazoline 3-oxide, The action of hydrogen chloride on these compounds and on 2,4,4-trimethyl-5-phenyl-4H-imidazole 1-oxide gives products of the addition of water or alcohol — derivatives of 4-hydroxy-2-imidazolinium chlorides.