Stable nitroxyl radicals with triple bonds: 4-acetylenyl-3-imidazoline-3-oxide-1-oxyls

Cross-coupling reaction of 1-hydroxy-2,2,5,5-tetramethyl-4-[2-(p-iodophenyl)vinyl]-3-imidazoline-3-oxide with copper(I) salts of 1-aryl(hetaryl)alkynes leads to the corresponding 2,2,5,5-tetramethyl-4-[2-(p-aryl(hetaryl)ethynylphenyl)vinyl]-3-imidazoline-3-oxide-1-oxyls in high yields.     

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.     

First acetylenic derivatives of stable 3-imidazoline nitroxides

The Stephens-Castro reaction of copper(I) salts of 1-aryl(hetaryl)alkynes with 2,2,5,5-tetramethyl-4-[2-(4-iodophenyl)-vinyl]imidazoline-3-oxide-1-ol proved to be a general method for the preparation of 2,2,5,5-tetramethyl-4-[2-(p-aryl(hetaryl)ethynylphenyl)]vinyl-3-imidazoline-3-oxide-1-oxyles.     

Reaction of amides of 3-imidazoline and 3-imidazoline-3-oxide derivatives with sodium hypobromite

Conclusions The reaction of 2,2,5,5-tetramethyl-3-imidazoline-1-oxyl-4-carboxamide with sodium hypobromite leads to 4-amino-2,2,5,5-tetramethyl-3-imidazoline-1-oxyl. 2,2,5,5-Tetramethyl-3-imidazoline-3-oxide-1-oxyl-4-carboxamide under the same conditions gives 3-hydroxy-2,2,5,5-tetramethylimidazolidin-4-one-1-oxyl.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 228–231, January, 1979.     

Modulation effects in the electron spin echo of trans bis-(2,2,5,5-tetramethyl-3-imidazoline-3-oxide-1-oxyl-4-il) ethylene biradicals

Electron spin echo modulation effects have been investigated in trans bis(2,2,5,5-tetramethyl-3-imidazoline-3-oxide-1-oxyl-4-il) ethylene biradicals involving ¹⁴N or ¹⁵N nuclei in different positions. The modulation frequencies are shown to be the nitrogen nuclear transition frequencies in radical fragments at m_S = 0 of a triplet electronic spin. Quadrupole splitting parameters for these nitrogen nuclei have been determined.     

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.     

Synthesis of block copolymers from polyvinyl chloride prepared in the presence of nitroxyl radicals of the imidazoline series

Specific features of radical polymerization of vinyl chloride in the presence of nitroxyl radicals of the imidazoline series (2-methyl-2,3-diphenyl-1,4-diazaspiro[4,5]dec-3-ene-1-oxyl, 2,2,5,5-tetramethyl-4-phenyl-2,5-dihydroimidazole-1-oxyl, 2,2,5-trimethyl-4,5-diphenyl-2,5-dihydroimidazole-1-oxyl) were studied. The possibility of preparing vinyl chloride-styrene block copolymers in the presence of these nitroxyl radicals was demonstrated, suggesting the occurrence of the polymerization by the reversible inhibition mechanism. The molecular-mass characteristics and the glass transition points of the synthesized samples were determined.     

Synthesis,crystal structure and ferromagnetic interactions of a silver(I) complex with imizadolyl-substituted nitroxide radicals

A silver(I) complex with nitronyl nitroxide, [Ag₂(NIT-R)₄(NO₃)₂]?·?CH₃OH [NIT-R?=?2-(5-methylimidazol-4-yl)-4,4,5,5-tetramethyl-2-imidazoline-1-oxyl-3-oxide], has been prepared and characterized by magnetic and single-crystal X-ray diffraction studies. In the complex, the silver(I) ion is coordinated with two monodentate nitronyl nitroxide radicals by the nitrogen of the imizadole ring. The silver(I) ion is two-coordinate and forms a dimer through Ag?···?Ag weak metal bonding interactions. The magnetic properties for the title complex have been investigated in the temperature range 2?～?300?K showing ferromagnetic interactions between the coordinated nitronyl nitroxides (J?=?3.64?cm^?1) and intermolecular antiferromagnetic interactions.     

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.     

Syntheses and Study of a Pyrroline Nitroxide Condensed Phospholene Oxide and a Pyrroline Nitroxide Attached Diphenylphosphine

The reaction of a diene nitroxide precursor with dichlorophenylphosphine in a McCormac procedure afforded 1,1,3,3-tetramethyl-5-phenyl-1,2,3,4,5,6-hexahydrophospholo[3,4-c]pyrrole-5-oxide-2-oxyl. Lithiation of the protected 3-iodo-pyrroline nitroxide followed by treatment with chlorodiphenylphosphine after deprotection afforded (1-oxyl-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-3-yl)diphenylphosphine oxide, and after reduction, (1-oxyl-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-3-yl)diphenylphosphine was realized, which was also supported by X-ray single crystal diffraction measurements. This pyrroline diphenylphosphine derivative was converted to hexadecylphosphonium salt, which is an analogue of antineoplastic agent, MITO-CP.     

Cyanoacetylene and Its Derivatives: XXVIII. Reactions of 2-Mercaptobenzothiazole with Nitriles of αα,ββ-Acetylene γγ-Hydroxyacids and with 3-Phenyl-2-propynonitrile

Nucleophilic addition of 2-mercaptobenzothiazole to 4-alkyl-4-hydroxy-2-alkynonitriles at 1:1 ratio in the presence of 4-6 wt% of Et₃N occurs regio- and stereospecifically to afford (Z)-4-alkyl-3-(benzothiazolyl-2-thio)-4-hydroxy-2-alkenonitriles (yield 40-51%). In the presence of 1.3 wt% of Dabco the thiazole and 4-hydroxy-4-methyl-2-pentynonitrile (1:1) give rise to a mixture of 2-alkenonitrile and 2-(3,3,6,6-tetramethyl-2-cyanomethyl-5-cyanomethylene-1,4-oxathian-2-yl)thiobenzothiazole. At the use of 4-6 wt% of LiOH arises an intractable mixture containing 1,4-oxathiane, benzothiazol-2-one, 2-[1-(5,5-dimethyl-2-cyanomethyl)-4-cyanomethylene-1,3-oxathiolan-2-yl)-1-methylethyl]thiobenzothiazole, bis(2,2,5,5-tetramethyl-6-cyanomethyl-3-cyanomethylene-1,4-oxathian-6-yl) disulfide, bis[1-(5,5-dimethyl-2-cyanomethyl-4-cyanomethylene-1,3-oxathiolan-2-yl)-1-methylethyl] disulfide, and 3-[1-(5,5-dimethyl-2-cyanomethyl-4-cyanomethylene-1,3-oxathiolan-2-yl)-1-methylethyl]benzothiazol-2-one (according to ¹H and ¹³C NMR data). 2-mercaptobenzothiazole adds to 3-phenyl-2-propynonitrile in the presence of 7 wt% of KOH with regio- and stereospecific formation of (Z)-3-(benzothiazolyl-2-thio)-3-phenyl-2-propenonitrile (88%).     

Cross-coupling of aryl iodides with paramagnetic terminal acetylenes derived from 4,4,5,5-tetramethyl-2-imidazoline-1-oxyl 3-oxide

2-(Arylylethynylphenyl)-4,4,5,5-tetramethyl-2-imidazoline-1-oxyl 3-oxides 12 and 13 were synthesized by cross-coupling of aryl iodides with 1-alkynes containing the 4,4,5,5-tetramethyl-2-imidazoline-1-oxyl 3-oxide fragment. A procedure was developed for the preparation of 3- and 4-ethynylbenzaldehydes with the use of 2-methylbut-3-yn-2-ol.     

Synthese von substituierten Calcium-bis(disilylamiden) mittels der Transmetallierung von Zinn(II)- und Zinn(IV)-amiden

Synthesis of Substituted Calcium-bis(disilylamides) by Transmetalation of Tin(II) and Tin(IV) Amides Stannylenes as well as stannanes with substituted disilylamino groups are valuable synthons for the synthesis of alkaline earth metal bis(disilylamides) via the transmetallation reaction. Whereas bis[2,2,5,5-tetramethyl-2,5-disilaaza-cyclo-pentyl]stannylene 1 is a suitable reagent for this type of reaction, bis[trimethylsilyl-tris(trimethylsilyl)silylamino]stannylene 2 (monoclinic, P2₁/c, a = 1492.6(2), b = 1705.2(2), c = 1865.3(3) pm, β = 109.03(2)º, Z = 4) is not only attacked at the Sn? N-bond but also the N? Si-bond is cleaved by calcium metal. Similar light sensitivity as for 2 is observed for the mercury bis[trimethylsilyl-tris(trimethylsilyl)silylamide] 3 , the homolytic M? N-bond cleavage leads to the formation of the trimethylsilyl-tris(trimethylsilyl)silylamino radical (g = 2.00485; a(N) = 16.2 G). The calcium tin exchange reaction of 1 in THF yields tris(tetrahydrofuran-O)calcium-bis[2,2,5,5-tetramethyl-2,5-disilaaza-cyclo-pentanide] 4 (monoclinic, P2₁/n, a = 1060.9(2), b = 1919.3(5), c = 1686.0(3) pm, β = 90.30(2)º, Z = 4). The stannanes Me_n-4Sn[N(SiMe₃)₂]_n with n = 1 or 2 are also valuable materials for the synthesis of bis(tetrahydrofuran-O)calcium-bis[bis(trimethylsilyl)amide].     

Synthesis of new highly organosoluble metallophthalocyanines with 1,8-dioxo-octahydroxanthene substituents

New highly organosoluble metallophthalocyanines (M = Zn, Co, Ni and Cu) bearing four [4-(3,3,6,6-tetramethyl-1,8-dioxo-2,3,4,5,6,7,8,9-octahydro-1H-xanthen-9-yl)phenoxy] substituents at peripheral positions have been prepared by tetramerization of 4-[4-(3,3,6,6-tetramethyl-1,8-dioxo-dodecahydro-1H-xanthen-9-yl)phenoxy]phthalonitrile in 2-(dimethylamino)ethanol using microwave irradiation or conventional heating. Ni(II), Co(II), and Cu(I) chloride were employed in order to synthesize the corresponding metal phthalocyanines and Zn(OAc)₂ was used for the preparation of the zinc phthalocyanines. 4-[4-(3,3,6,6-Tetramethyl-1,8-dioxo-2,3,4,5,6,7,8,9-octahydro-1H-xanthen-9-yl)phenoxy]phthalonitrile was obtained by nucleophilic displacement of the nitro group in 4-nitrophthalonitrile with 9-(4-hydroxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7-tetrahydro-2H-xanthene-1,8(5H,9H)-dione. 9-(4-Hydroxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7-tetrahydro-2H-xanthene-1,8(5H,9H)-dione was synthesized efficiently from dimedone and 4-hydroxybenzaldehyde. All the phthalocyanines are soluble in DMSO, DMF, CHCl₃, THF, CH₂Cl₂, and CH₃CN. The new compounds were characterized by IR, NMR, and UV–vis spectroscopy, elemental analysis, and thermogravimetric analysis.     

Synthesis and structure of products of hydroxylamine acylation with 3-carboxy-2,2,5,5-tetramethylpyrrolinoxyl derivatives

The reaction of NH₂OH with the derivatives of 2,2,5,5-tetramethylpyrrolin-1-oxyl-3-carboxylic acid in all events led to the formation of a mixture of the corresponding nitroxylhydroxamic acid with a stable O-acylhydroxylamine. The ratio between the products depends on the nature of the acylating agent and under the studied conditions varies from ∼5.5: 1 to 1: 3 indicating the comparable nucleophilicity in this reaction of N and O atoms in the hydroxylamine. The most active chloride of the mentioned acid alongside the indicated products afforded in a considerable yield N,O-diacylhydroxylamine and the triacylated hydroxylamine, 3-{[(2,2,5,5-tetramethyl-1-oxylopyrrolin-3-yl)carbonyloxyimino][(2,2,5,5-tetramethyl-1-oxylopyrrolin-3-yl)carbonyloxy]-methyl}-2,2,5,5-tetramethylpyrrolin-1-oxyl. The structure of both latter compounds was established by XRD analysis.     

Behavior of 1-hydroxy-2,2,5,5-tetramethyl-3-imidazoline-3-oxide and the corresponding nitroxyl radicals in superacid media

The protonation of 1-R-2,2,5,5-tetramethyl-3-imidazoline-3-oxides (R=OH, O) in superacid media was investigated with¹H and¹³C NMR. The hydroxylamino dication forming on protonation can undergo imidazoline ring opening to form an isomeric mixture of diprotonated N-(2-hydroxyimino-1,1-dimethylethyl),,-dimethylnitrones.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2755–2761, December, 1991.     

Complexes of nickel(ii) and copper(ii) chlorides with a nitroxide radical derivative of 4-tetrazolyl-3-imidazolme-3-oxide

NiCl₂ and CuCl₂ complexes with a new stable nitroxyl radical, 2,2,5,5-tetramethyl-4-(tetrazol-5-yl)-3-imidazoline-3-oxide-1-oxyl (L), NiLCl₂· H₂O and CuLCl₂, have been synthesized. The _eff values attest to a weak exchange interaction between the paramagnetic centers in the temperature interval of 78–300 K.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 932–934, May, 1994.The authors are grateful to E. G. Boguslavskii for the registration and interpretation of the ESR spectrum, to V. A. Shipachev for the measurement of SDR, and to V. I. Lisoivan for the X-ray analysis.     

Ritter reaction. Synthesis of 1-substituted 3,3,7,9-tetramethyl-2-azaspiro[4.5]deca-6,9-dien- and -1,6,9-trien-8-ones and 7-methoxy-3,3,6,8-tetramethyl-3,4-dihydroisoquinolines

1-(4-Methoxy-3,5-dimethylphenyl)-2-methylpropan-1-ol reacted with nitriles [MeSCN, PhCN, MeCN, EtOC(O)CH₂CN] in the presence of concentrated sulfuric acid to give both 1-R-3,3,7,9-tetramethyl-2-azaspiro[4,5]deca-6,9-dien- and -1,6,9-trien-8-ones and 1-R-7-methoxy-3,3,6,8-tetramethyl-3,4-dihydroisoquinolines. The reaction with 3,4-dimethoxyphenylacetonitrile afforded 10,11-dimethoxy-1,3,6,6-tetramethyl-1,5,6,12b-tetrahydrodibenzo[d,f]indole-2,8-dione. Three-component condensation of 2-methoxy-1,3-dimethylbenzene with isobutyraldehyde and nitriles led to the formation of spirocyclic systems and 3,4-dihydroisoquinoline derivatives in lower yield.     

Magnetic resonance studies of imidazoline nitroxides and their photochemical transformations

ESR, ¹H and ¹³C NMR, ENDOR and TRIPLE resonance have been employed to study photochemical reactions of 2,2,5,5-tetramethyl-4-phenyl-3-imidazoline-3-oxide-1-oxyl and to determine the electronic structures of the initial and final radicals. The light-induced isomerization of a phenyl nitron group to an oxaziridine group has been shown to proceed without involving the radical centre.     

Synthesis and structure of 3-(hydroxycarbamoyl)-2,2,5,5-tetramethyl-2,5-dihydropyrrol-1-oxyl

Hydroxyamination of 3-chlorocarbonyl-2,2,5,5-tetramethyl-2,5-dihydropyrrol-1-oxyl gave previously unknown 3-(hydroxycarbamoyl)-2,2,5,5-tetramethyl-2,5-dihydropyrrol-1-oxyl whose structure was determined by X-ray analysis. The hydroxamic acid fragment has cis configuration, and the carbonyl group occupies distorted trans position with respect to the double bond in the planar dihydropyrrole ring.