Reactions of heterocyclic paramagnetic aldonitrone, 2,2,5,5-tetramethyl-3-imidazoline-1-oxyl 3-oxide, with alkynes

The reactions of heterocyclic paramagnetic aldonitrone,viz., 2,2,5,5-tetramethyl-3-imidazoline-1-oxyl 3-oxide, with mono- and disubstituted alkynes afford unstable isoxazoline derivatives. The reactions with monosubstituted alkynes yield predominantly 5-substituted regioisomers. The resulting isoxazoline derivatives are readily (and often spontaneously) converted into enaminoketones,viz, imidazolidine-1-oxyl derivatives. In the presence of tolan, the title paramagnetic aldonitrone gives a dimer in which one imidazoline ring undergoes profound transformation. The structure of the resulting dimer was established by X-ray diffraction analysis. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 112–117, January, 2000.     

Synthesis and properties of the first representatives of terminal acetylenes in 3-imidazoline-1-oxyl 3-oxide series

Method for the synthesis of m-and p-isomers of 4-[2-(ethynylphenyl)vinyl]-2,2,5,5-tetramethyl-3-imidazoline-1-oxyl 3-oxides by the cross-coupling of 4-[2-(3-iodophenyl)vinyl]-and 4-[2-(4-iodophenyl)vinyl]-2,2,5,5-tetramethyl-3-imidazoline-1-oxyl 3-oxides with (trimethylsilyl)acetylene followed by desilylation was elaborated. The reactions at the CH-fragment of the ethynyl group were performed. The Mannich reaction proceeds with the loss of a spin label, whereas the oxidative homocoupling, with its retention. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2051–2054, October, 2007.     

Reactions of heterocyclic paramagnetic aldonitrone, 2,2,5,5-tetramethyl-3-imidazoline-1-oxyl 3-oxide, with alkynes

The reactions of heterocyclic paramagnetic aldonitrone,viz., 2,2,5,5-tetramethyl-3-imidazoline-1-oxyl 3-oxide, with mono- and disubstituted alkynes afford unstable isoxazoline derivatives. The reactions with monosubstituted alkynes yield predominantly 5-substituted regioisomers. The resulting isoxazoline derivatives are readily (and often spontaneously) converted into enaminoketones,viz, imidazolidine-1-oxyl derivatives. In the presence of tolan, the title paramagnetic aldonitrone gives a dimer in which one imidazoline ring undergoes profound transformation. The structure of the resulting dimer was established by X-ray diffraction analysis. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 112–117, January, 2000.     

Synthesis of 2,2,5,5-tetramethyl-3-imidazoline-1-oxyl

Condensation of -(hydroxylamino)-2-methylpropanal with acetone and ammonia afforded 2,2,5,5-tetramethyl-3-imidazoline-1-oxyl, the first member of a series of stable nitroxyl radicals which are derivatives of 3-imidazoline. It was shown that 2,2,5,5-tetramethyl-2, 5-dihydropyrazine-1,4-dioxide can reversibly add two molecules of water or ammonia to the nitrone groups.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 931–933, May, 1993.     

The formation of nitroxyl radicals in reactions of dimethyldioxirane with 2,2,6,6-tetramethylpiperidine and 2,2,5,5-tetramethyl-3-imidazoline-3-oxide derivatives

The oxidation of secondary and tertiary amines, derivatives of 2,2,6,6-tetramethylpiperidine and 2,2,5,5-tetramethyl-3-imidazoline-3-oxide, by dimethyldioxirane results in the formation of nitroxyl radicals, which induce the decomposition of dimethyldioxirane. Chemiluminescence in the IR and visible regions during the reaction of dimethyldioxirane with 2,2,6,6-tetramethyl-4-hydroxypieeridine-1-oxyl was observed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2501–2503, December, 1998.     

Structure and Magnetic Properties of the Stable Nitroxide 2-Cyano-4,4,5,5-tetramethyl-3-oxide-2-imidazoline-1-oxyl

Crystal and molecular structure of the nitroxide 2-cyano-4,4,5,5-tetramethyl-3-oxide-2-imidazoline-1-oxyl was studied. The nontrivial features of the structure are coplanarity of all atoms of the 2-imidazoline heterocycle and the nitrile group bonded to it and short intermolecular contacts between the nitroxyl O atoms and the C atoms in the 2 position of the heterocycles of the neighboring molecules, actually forming layers in the crystal structure. These data agree with the results of magnetic studies, which are well approximated by the two-dimensional model, which is a rare occurrence for organic magnets.     

Cu_2O/丁二酮肟催化芳基碘与芳胺偶联反应研究

钯催化的Ullmann反应合成C-N键获得成功~([1-3]),在各种配体参与下廉价的铜催化Ullmann反应形成C-N键,引起了人们的关注~([4-5]).配体在活化铜催化的偶联反应中非常关键,就此类催化体系所选的配体而言,目前报道的主要有N,N配体(如1,10-邻菲咯啉~([6])和二胺~([7])等)、N,-COOH配体(如氨基酸~([4]))、O,O配体(如联萘二酚~([8])和1,3-二酮~([9]))、N,P配体~([10-11])等,作者也曾用空气稳定的三价膦配体促进了此类反应~([12]).     

4-Hydroxyiminonitromethyl-2,2,5,5-tetramethyl-3-imidazolme-1-oxyl as a precursor of spin-labeled nitrile oxide

Paramagnetic nitrile oxide, a derivative of 3-imidazoline-1-oxyl, has been generated by thermolysis of geminal nitrooxime. This compound readily undergoes cycloaddition with alkenes with both activated and nonactivated C=C bonds. The paramagnetic nitrile oxide may be used for introducing a nitroxyl into molecules with multiple carbon-carbon bonds.For the previous communication, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 289–291, February, 1994.     

New derivatives of 4,4,5,5-tetramethyl-4,5-dihydro-1-H-imidazol-1-oxyl 3-oxide as monomers for polyradicals with special magnetic properties

The preparation of new derivatives of 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide as monomers for purely organic polymers with special magnetic properties is described. 3,5-Diethynylbenzaldehyde and 3,5-bis(trimethylsilylethynyl)benzaldehyde were converted to the corresponding 1,3-dihydroxy-4,4,5,5-tetramethylimidazolidine derivatives which were oxidized to stable nitronyl nitroxide radicals.     

Seven-membered metallocycle in the CuII complex with deprotonated 2-(2-hydroxy-3-nitrophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl 3-oxide

The reaction of CuCl₂ with deprotonated 2-(2-hydroxy-3-nitrophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl 3-oxide afforded a bis-chelate complex containing seven-membered metallocycles.     

CuI/PPh3‐catalyzed Sonogashira coupling reaction of aryl iodides with terminal alkynes in water in the absence of palladium

The Sonogashira cross‐coupling of aryl iodides with terminal alkynes catalyzed by a simple and inexpensive catalyst system of CuI/PPh₃ in water as the sole solvent has been reported. In the presence of CuI/PPh₃, with KOH used as a base, a number of aryl iodides were treated with alkynes to afford the corresponding products in moderate to excellent yields. Copyright © 2008 John Wiley & Sons, Ltd.     

Reaction of 4H- and 2H-imidazole oxides with organolithium compounds,a novel route to stable nitroxyl radicals of the 2(3)-imidazoline series

Reactions of 4H and 2H-imidazole oxides with phenyl- and methyilithium followed by oxidation afford stable nitroxyl radicals — derivatives of 2- and 3-imidazolines including otherwise inaccessible sterically hindered radicals of the latter group. An unusual reaction, the formation of 2-azabutadiene derivatives after NO elimination in the dark, has been observed for pentaphenyl- and 5-methyltetraphenyl-3-imidazoline-1-oxyls.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 933–936, May, 1993.     

Spin transition in the molecular heterospin complex of Cu(hfac)2 with 4,4,5,5-tetramethyl-2-(1-methylpyrazol-5-yl)-4,5-dihydroimidazole-1-oxyl 3-oxide

The synthesis, structure, and magnetic properties of the products of the reaction for Cu(hfac)₂ (hfac is hexafluoroacetylacetonate) with spin-labeled nitronyl nitroxides 4,4,5,5-tetramethyl-2-(1-R-1H-pyrazol-5-yl)-3-imidazoline-1-oxyl 3-oxides L^5/R (R = Me, Et, Pr, Bu), viz., binuclear complex [Cu(hfac)₂L^5/Me]₂ and chain polymer complexes [Cu(hfac)₂L^5/R]_n, are described. The polymer heterospin chains are built according to “head-to-head” (R = Me, Et, Pr, Bu) and “head-to-tail” (R = Pr, Bu) motifs. Compound [Cu(hfac)₂L^5/Me]₂ is characterized by the ability to reveal the reversible effect of thermally induced spin transition at a temperature about 75 K (without hysteresis). In the set of heterospin Cu^II compounds with spin-labeled pyrazoles, this is the earlier unknown example of a molecular complex exhibiting a similar magnetic anomaly.     

Crystallography and magnetism of radicals with hindered hydroxyl groups: 2-(3,5-di-tert-butyl-4-hydroxyphenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl and 2-(3,5-di-tert-butyl-4-hydroxyphenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl

Radicals form networks of OH...ON and OH...Me(nitroxide) interactions. In 2, a frustrated network forms with insufficient N-O units to form extended chain interactions. The magnetism of 1 fits a 1-D Heisenberg model with J/k=-25 J mol(-1), while 2 shows more complex exchange behaviour consistent with its disordered crystal lattice.     

Electronic structure of the organic half-metallic magnet: 2-(5-pyrimidinyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-3-oxoimidazol-1-oxyl

An accurate full-potential density-functional method is used to study the magnetic and half-metallic properties in the pure organic materials: 2-(5-pyrimidinyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-3-oxoimidazol-1-oxyl. The total and partial density of states and atomic spin magnetic moments are calculated and discussed. It is found that the unpaired electrons in this compound are localized in a molecular orbital constituted primarily of π^*(NO) orbital, and the main contribution of the spin magnetic moment comes from the NO free radicals. It is predicted that this compound is half-metallic magnet. It is also found that there exists ferromagnetic intermolecular interaction in the compound.     

Ligand‐free Pd/Cu‐catalyzed decarboxylative coupling of aryl iodides with α‐oxocarboxylates

This paper describes a palladium/copper‐catalyzed decarboxylative coupling of aryl iodides with α‐oxocarboxylates. The cross‐coupling reaction gives high chemical yields of aryl ketones and has wide functional group tolerance, making the transformation an attractive alternative to the traditional cross‐coupling approaches for aryl ketones. Copyright © 2014 John Wiley & Sons, Ltd.     

BiCl3‐catalyzed carbon‒carbon cross‐coupling of organoboronic acids with aryl iodides

A procedure for BiCl₃‐catalyzed carbon‐carbon cross‐coupling reaction of organoboronic acids with aryl iodides is described. This protocol has a wide substrate scope and uses an inexpensive and non‐toxic catalyst. Copyright © 2013 John Wiley & Sons, Ltd.