Synthesis of 2,2,6,6-tetramethyl-1-oxyl-4-piperidyloxy-tert-butylperoxyalkylsilanes

2,2,6,6-Tetramethyl-1-oxyl-4-piperidyloxy-tert-butylperoxyalkylsilanes were obtained by condensation of 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl with organosilicon chloroperoxides ClR₂SiOOR' (R = Me, Et; R' = Bu^t) in ether at 0–5 °C in the presence of a tertiary amine as an HCl acceptor.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 984–985, May, 1995.     

Electrocatalytic oxidation of benzoyl hydrazine in the presence of 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl

2,2,6,6-Tetramethyl-4-hydroxypiperidine-1-oxyl (TMHPO) shows catalytic electroactivity in homogeneous oxidation of benzoyl hydrazine (BH) on a glassy carbon electrode. The catalytic current is affected by the concentration of TMHPO and the pH of the solution. A possible catalytic reaction mechanism is proposed and a non-toxic, convenient method for the determination of BH in the concentration range 1×10⁻⁵–2×10⁻³ M has been developed.     

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.     

Peculiarities of the reaction of 2,2,6,6-tetramethylpiperidin-1-oxyl with Cp2TiEtCl

The reaction of 2,2,6,6-tetramethylpiperidin-1-oxyl (1) with Cp₂TiEtCl (2) has been studied. The consumption of1 and evolution of gaseous products (ethane, ethylene) proceed with autoacceleration. Increasing the1 : 2 molar ratio leads to inhibition of the autoacceleration. The fact that the yield of ethane is higher than that of ethylene indicates that the reaction proceedsvia S_R2 substitution of the ethyl group in Cp₂TiEtCl for radical1. The mechanism of the substitution is synchronous, A kinetic model of the reaction has been proposed and substantiated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2904–2908, December, 1996.     

Complex formation between chlorine dioxide and 2,2,6,6-tetramethylpiperidin-1-oxyl

The complex formation of ClO₂ with 2,2,6,6-tetramethylpiperidin-1-oxyl (TMPO) in acetone, acetonitrile,n-heptane, diethyl ether, carbon tetrachloride, and toluene was studied spectrophotometrically at −20 to +20 °C. The thermodynamic parameters of complex formation were determined at 20 °C. The transformation of the complex into the oxoammonium salt TMPO⁺ClO ₂ ⁻ was found. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1703–1706, October, 2000.     

Kinetic Investigation of the Reaction of Octacarbonyl Dicobalt with 2,2,6,6-Tetramethylpiperidin-1-oxyl

The initial rate of carbon monoxide evolution in the reaction of Octacarbonyl dicobalt with 2,2,6,6-tetramethylpiperidin-1-oxyl free radical (TEMPO) at 15°C in n-octane solution leading to the 16e complex (TEMPO)Co(CO)₂ was found to be first order with respect to the TEMPO concentration, 0.5 order with respect to the Co₂(CO)₈ concentration, and negative 0.5 order with respect to the CO concentration. Scavenging ·Co(CO)₄ and ·Co(CO)₃ by the free radical TEMPO in the rate-determining steps are in accord with the kinetic observation. The observed rate constant is k _obs = 6.4 × 10^–5 s^–1.     

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.     

Aerobic Oxidation of Benzyl Alcohol Catalyzed by Cu-Mn Mixed Oxides and 2,2,6,6-Tetramethyl-piperidyl-1-oxyl

Heterogeneous Cu-Mn mixed oxides can mediate TEMPO-catalyzed selective oxidation of benzyl alcohol by molecular oxygen under neutral condition, and is recyclable. In the case of the molar ratio of Cu and Mn over 1, the highly-dispersed CuO inside the Cu-Mn mixed oxides is responsible for the good performances in catalytic oxidation.     

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     

Electrochemical modeling of the reaction of 1-Chloro- and 1-Bromo-2,2,6,6-tetramethylpiperidine photolysis

Electrolysis of 1-Chloro- and 1-Bromo-2,2,6,6-tetramethylpiperidines yields free nitroxyl radical 2,2,6,6-tetramethylpiperidine-1-oxyl. The reaction mechanism is suggested, which is based on the intermediate formation of aminyl radical. Concurrently with the nitroxyl radical formation, electrochemical chlorination of 2,2,6,6-tetramethylpiperidine occurs. It is shown that the 2,2,6,6-tetramethylpiperidine can be used as a mediator in the electrochemical oxidation of alcohols.     

Use of 1,4-bis(2,2,6,6-tetramethyl-1-oxyl-4-piperidyl)butane as a probe for studying acid sites

ESR spectroscopy was applied to study paramagnetic complexes of the nitroxyl biradical of 1,4-bis(2,2,6,6-tetramethyl-1-oxyl-4-piperidyl)butane formed with AlCl₃ in a toluene solution and resulted from the interaction with the acid sites on the SiO₂ and γ-Al₂O₃ surface. This biradical in solution forms a complex with two AlCl₃ molecules, and a complex with two hydroxyl groups is formed on the SiO₂ surface. When the biradical is adsorbed on the γ-Al₂O₃ surface, complex formation is complicated because of steric hindrance preventing bidentate coordination. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 165–167, January, 2007.     

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.     

The effect of the nature of the substituent at the nitrogen atom on transformations of 3-bromo-2,2,6,6-tetramethyl-4-piperidinone and its 1-hydroxy and 1-oxyl derivatives under conditions of the Favorsky rearrangement

3-Bromo-2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl reacts with NH₄OH to give 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl, a product of the Favorsky rearrangement. 3-Bromo-2,2,6,6-tetramethyl-4-piperidinone is transformed under these conditions into a bicyclic amino ketone, while its 1-hydroxy derivative affords acyclic nitrosoenone. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1189–1191, June, 1997.     

Kinetic Study of Chelates of 2,2,6,6-tetramethyl-3,5-heptanedione with Some Lanthanide Elements

The thermal decomposition reactions of crystalline chelates of general formula Ln(thd)₃ (Ln=La,Pr, Nd, Sm and Gd; thd=2,2,6,6-tetramethyl-3,5-heptanedione) have been studied by isothermal thermogravimetry. Several models were proposed initially to calculate the kinetic parameters by isothermal method, thus the time reduced method was used to define the best kinetic models. The Avrami–Erofeev (Am=2, 3 and 4) and R1 and R2 models presented good agreement with experimental data, as well as, linear correlation coefficient (r) and standard deviation (s). This revised version was published online in July 2006 with corrections to the Cover Date.     

Vinyl ether of 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl and its oligomers

Russian Chemical Bulletin -     

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     

交联聚苯乙烯微球固载2,2,6,6-四甲基哌啶氮氧自由基的催化氧化性能与机理

将交联聚苯乙烯(CPS)微球表面固载有2,2,6,6-四甲基哌啶氮氧自由基(TEMPO)的非均相催化剂微球(TEMPO/CPS)与过渡金属盐相结合,构成复合催化剂体系,用于分子氧对肉桂醇的氧化过程的研究。 分别采用高价金属离子氧化性比硝酸根NO3-更弱和更强的两类过渡金属盐为助催化剂,与微球TEMPO/CPS构成组合催化剂,深入探索研究了其催化性能与催化机理。 研究结果表明,几种过渡金属盐(如Fe、Cu、Mn、Co盐)与微球TEMPO/CPS形成的复合催化剂,可有效地催化分子氧对肉桂醇的氧化过程,将其转化为唯一的产物肉桂醛。 以过渡金属硝酸盐为助催化剂,当硝酸盐结构中对应的高价态(氧化态)金属离子的氧化性比NO3-离子弱时(如Fe(NO₃)₃与Cu(NO₃)₂),正负离子共同发挥助催化作用;当硝酸盐结构中对应的高价态(氧化态)金属离子的氧化性比NO3-离子强时,比如Co(NO₃)₂与Mn(NO₃)₂对应的Co(Ⅲ)与Mn(Ⅲ)离子,金属离子单独发挥助催化作用,NO3-离子不起作用。 实验结果表明,对于肉桂醇的分子氧催化氧化,在几种过渡金属盐中,Fe(NO₃)₃作为最适宜的助催化剂,温和条件下(55 ℃、常压O₂),可高效地将肉桂醇转化为肉桂醛,转化率为92%。     

Alkylation of 2,2,6,6-tetr amethyl-4-oxopiperidine and 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl enamines by mannich bases from β-naphthol

Conclusions The alkylation of 2,2,6,6-tetramethyl-4-oxopiperidine and 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl enamines gave paramagnetic compounds that contain the pyran ring.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1668–1670, July, 1978.