Synthesis and structure of diastereomeric trans-3,4-diamino-2,2,6,6-tetramethylpiperidine1-oxyl derivatives

The reaction of 3,4-diamino-2,2,6,6-tetramethylpiperidine-1-oxyl with (1S)-(+)-camphor-10-sulfonyl chloride gives a mixture of diastereomeric 4-monosulfonylamino derivatives. The products of their acylation have been obtained. The 3,4-bis-[(1S)-camphor-10-sulfonylamino] derivative was synthesized and resolved to individual diastereomers. For one of them thetrans relationship of the 3- and 4-substituents and the absolute (3S,4R)-configuration were established by X-ray structural analysis.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 367–372, February, 1993.     

Interaction of 2,2,6,6-tetramethylpiperidine-1-oxyl chloritewith alcohols

The kinetics of the oxidation of a series of alcohols (viz., ethanol, propan-2-ol, butan-1-ol, butan-2-ol, heptan-4-ol, decan-2-ol, propan-1,3-diol, butan-2,3-diol, cyclohexanol, benzyl alcohol, and borneol) with the oxoammonium salt 2,2,6,6-tetramethylpiperidine-1-oxyl chlorite in acetonitrile was studied by spectrophotometry. The products of oxidation of primary alcohols are the corresponding aldehydes and carboxylic acids, and the products of oxidation of secondary alcohols are ketones. The reaction rate is described by the second order equation. The rate constants and activation parameters were determined. The rate constant as a function of the alcohol nature is described by the one-parameter Taft equation.     

Synthesis and properties of 3,5-dibromo-4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl radical

Bromination of 1-hydroxy-4-oxo-2,2,6,6-tetramethylpiperidine gives 3,5-dibromo-1-hydroxy-4-oxo-2,2,6,6-tetramethylpiperidine hydrobromide. Oxidation of the latter generates 3,5-dibromo-4-oxo-2,2,6,6-tetramethylpiperdine-1-oxyl radical, which represents a convenient acylating spin trap.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 73–74, January, 1992.     

Synthesis of well-defined polychlorostyrenes by living radical polymerization with 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl

Radical polymerization of 2-, 3-, and 4-chlorostyrenes (ClSts) was investigated with benzoyl peroxide (BPO) as an initiator, in the presence of 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO). The polymerization was performed in bulk for 3.5 h at 95°C and then continued for a defined time at 125°C to give the corresponding poly(ClSt)s with narrow polydispersity in high yield. It was found that the polymerization proceeded in accordance with a living mechanism in all cases, because the molecular weight of the resulting polymers was proportional to the conversion, and inversely proportional to the initial concentration of MTEMPO. Furthermore, the polymers obtained from 2- and 3-ClSts quantitatively act as initiators for the polymerization in the living radical manner, of styrene to give the corresponding block copolymers, except for poly(4-ClSt). The thermal stability of the living poly(ClSt)s was found to decrease in the order of 2- > 3- > 4-ClSt on the basis of the results of their postpolymerizations. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2371–2378, 1997     

Photo-controlled/living radical polymerization mediated by 2,2,6,6-tetramethylpiperidine-1-oxyl in inert atmospheres

The photo-controlled/living radical polymerization of methyl methacrylate using a nitroxide mediator was established in an inert atmosphere. The bulk polymerization was performed at room temperature using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl as the mediator and (2RS,2′RS)-azobis(4-methoxy-2,4-dimethylvaleronitrile) as the initiator in the presence of (4-tert-butylphenyl)diphenylsulfonium triflate as the accelerator by irradiation with a high-pressure mercury lamp. The photopolymerization in a N₂ atmosphere produced a polymer with a comparatively narrow molecular weight distribution; however, the experimental molecular weight was slightly different from the theoretical molecular weight. The Ar atmospheric polymerization also provided a polymer with the molecular weight distribution similar to that of the polymer obtained by the N₂ atmospheric polymerization. These inert atmospheric polymerizations more rapidly proceeded to produce polymers with narrower molecular weight distributions than the vacuum polymerization. The livingness of the Ar atmospheric polymerization was confirmed on the basis of the first-order time–conversion plots and conversion–molecular weight plots.     

Photo-living radical polymerization of methyl methacrylate by 2,2,6,6-tetramethylpiperidine-1-oxyl in the presence of a photo-acid generator

The novel photo-living radical polymerization of methyl methacrylate (MMA) was determined using 2,2’-azobis(4-methoxy-2,4-dimethylvaleronitrile) (AMDV) and 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) in the presence of bis(alkylphenyl)iodonium hexafluorophosphate (BAI). The polymerization provided a comparatively narrow molecular weight distribution in the range of 1.4–1.7. The resulting PMMA contained no BAI fragments in its structure and had the 1-cyano-1,3-dimethyl-3-methoxybutyl radical and MTEMPO at the 1:1 molar ratio. The experimental molecular weight was in close agreement with the theoretical one when the initiator efficiency was taken into consideration. The plots of ln([MMA]₀/[MMA]) vs. time and the molecular weight of PMMA vs. the conversion and vs. the reciprocal of the initial concentration of AMDV showed linear correlations, indicating that the polymerization proceeded in accordance with a living mechanism. It was found that the polymerization had a photo-switching ability, because the polymerization was interrupted by turning off the irradiation, and then restarted by the irradiation again.     

Control of micellization induced by disproportionation of 2,2,6,6-tetramethylpiperidine-1-oxyl supported on side chains of a block copolymer

The block copolymer micellization induced by the disproportionation of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was performed using acids with different acid strengths. A poly(4-vinylbenzyloxy-TEMPO)-block-polystyrene diblock copolymer (PVTEMPO-b-PSt) produced micelles in 1,4-dioxane by the disproportionation of the TEMPO by HNO₃, HCl, HClO₄, and HSbF₆. The acid strength affected the efficiency of the micellization. The acid/VTEMPO molar ratio required for the micellization decreased with an increase in the acid strength: $ {\text{HNO}}_{\text{3}} < {\text{HCl}} < {\text{HClO}}_{\text{4}} < {\text{HSbF}}_{\text{6}} $ . The acid strength also made a difference in the hydrodyamic diameter of the micelles. The stronger acid provided larger micelles. This difference in the micellization was based on the difference in the solubility of the oxoaminium salt formed by the disproportionation of the TEMPO and on the steric hindrance of its counter anion.     

Dehydrogenation of nitro derivatives of bibenzyl to corresponding nitro stilbene with dioxygen catalyzed by 2,2,6,6-tetramethylpiperidine-1-oxyl

A simple and effective oxidative dehydrogenation of nitro derivatives of bibenzyl was developed using a mixture of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and metal salts as catalyst under an atmospheric pressure of oxygen. The oxidation of several nitro derivatives of bibenzyl led to corresponding nitro stilbene in good yields, and the yields increased with the increase in the substituted nitro group on the bibenzyl. For example, the aerobic dehydrogenation of 2,2??,4,4??,6,6??-hexanitrobibenzyl in the presence of a catalytic amount of TEMPO with metal salts gave 2,2??,4,4??,6,6??-hexanitrostilbene in 81?% yield and 4,4??-dinitrostilbene-2,2??-disulfonic acid (75?%) was obtained from 4,4??-dinitrobibenzyl-2,2??-disulfonic acid.     

Synthesis of 3,4-diamino-1H-pyrazolo[3,4-d]pyrimidines

The reaction of 4-(amino-substituted)-2-methylthio-6-chloropyrimidine-5-carbonitriles with hydrazine and methylhydrazine was used to synthesize 3, 4-diamino-6-methylthio-1H-pyrazolo[3, 4-d]pyrimidines. It was shown that the formation of pyrazolopyrimidines proceeds through intermediate 6-hydrazinopyrimidine-5-carbonitriles.Department of Organic Chemistry, Vil'nyus University, Vil'nyus 2006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 831–836, June, 1996. Original article submitted February 9, 1996.     

Synthesis and Crystal Structure of 4-Azido-2,2,6,6-Tetramethylpiperidine-1-oxyl Free Radical

1 INTRODUCTION Stable nitroxyl radicals are widely used in mole- cular biology, molecular pharmacology and phar- macy for noninvasive characterization of enzymes, receptors and drug delivery systems[1, 2]. They are al- so applied to examine the active center topography, the penetration of water, microviscosity, micropolo- rity, PH and oxygen concentration of their surroun- ding as well as spin carriers due to their exceptional stability and ease of chemical modification[3, 4]. However, th…     

Synthesis of 4-sulfonatooxy-2,2,6,6-tetramethylpiperidine-1-yloxyl derivatives for investigation of ionic liquids

Direct sulfonation of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-yloxyl using chlorosulfuric acid trimethylsilylester results in 4-sulfonatooxy-2,2,6,6-tetramethylpiperidine-1-yloxyl in 94% yield that is the basis for the synthesis of potassium 4-sulfonatooxy-2,2,6,6-tetramethylpiperidine-1-yloxyl and sodium 4-sulfonatooxy-2,2,6,6-tetramethylpiperidine-1-yloxyl. These nitroxides can be employed as spin probes to investigate properties of ionic liquids in the molecular domain.     

Preparative synthesis of 2,2,6,6-tetramethyl-4-oxopiperidin-1-oxyl

Summary When triacetonamine was slowly oxidized with an aqueous solution of hydrogen peroxide in the presence of sodium tungstate at room temperature, 2,2,6,6-tetramethyl-4-oxopiperidin-1-oxyl was obtained in good yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12 p. 2218, December, 1964     

Photo-controlled/living radical polymerization of 2-(dimethylamino)ethyl methacrylate using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl as a mediator

The photo-controlled/living radical polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) was attained using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl as the mediator and (2RS,2′RS)-azobis(4-methoxy-2,4-dimethylvaleronitrile) (r-AMDV) as the initiator. The bulk polymerization of DMAEMA produced a polymer with a comparatively narrow molecular weight distribution below 1.6. The first-order time conversion plots showed a linear increase. The molecular weight of the resulting polymer also increased with an increase in the monomer conversion. The molecular weights of the resulting polymers were in good agreement with the theoretical molecular weights. A linear correlation was also obtained for the plots of the molecular weight vs. the reciprocal of the initial concentration of r-AMDV. The GPC analysis demonstrated the living nature of the polymerization based on the fact that the curves were shifted to the higher molecular weight side without deactivation as the conversion increased.     

Synthesis of new stable free radicals in the 2,2,6,6,-tetramethylpiperidin-1-oxyl series

Conclusions A series of new individual 2,2,6,6-tetramethyl-1-oxyl-4-piperidyl amides and esters of carboxylic acids was synthesized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1191–1193, May, 1969.     

Synthesis of 4-trimethylammonio-2,2,6,6-tetramethylpiperidine-1-yloxyl with various anions for investigation of ionic liquids

A new synthetic way is described to prepare 4-trimethylammonio-2,2,6,6-tetramethylpiperidine-1-yloxyl bearing tetrafluoroborate, hexafluorophosphate or bis(trifluoromethylsulfonylimide) by an anion metathesis of 4-trimethylammonio-2,2,6,6-tetramethylpiperidine-1-yloxyl iodide using the corresponding silver salts. 4-Trimethylammonio-2,2,6,6-tetramethylpiperidine-1-yloxyl iodide is obtained by the methylation of 4-amino-2,2,6,6-tetramethylpiperidine-1-yloxyl with methyliodide. The new spin probe 4-trimethylammonio-2,2,6,6-tetramethylpiperidine-1-yloxyl bistrifluoromethylsulfonylimide and the spin probes containing tetrafluoroborate or hexafluorophosphate may be useful for an effective investigation of ionic liquids with similar anions.