Studies on Stable Free Radicals. XIII. Synthesis and ESR Spectral Properties of Hindered Piperazine <i>N</i>-Oxyls

Yoshioka, Toshimasa; Mori, Eiko; Murayama, Keisuke

doi:10.1246/bcsj.45.1855

Cited by 19 publications

(6 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…BODAZ was prepared according to a literature procedure27 in five synthetic steps from cyclohexanone in an overall yield of 65%. The final step involved oxidation of the corresponding amine with the reported m ‐chloroperbenzoic acid procedure 27. After recrystallization with hexane, orange needles of BODAZ were obtained in 60% yield.…”

Section: Methodsmentioning

confidence: 99%

“…In this study, we investigate the six‐membered cyclic nitroxide 2,6‐spirodicyclohexylpiperazinedione {BODAZ, [cyclohexane‐1‐spiro‐2′‐(3′,5′‐dioxo‐4′‐benzylpiperazine‐1′‐oxyl)‐6′‐spiro‐1″‐cyclohexane]}. BODAZ and NO88 are attractive nitroxides because they can be easily prepared from readily available starting materials 27. The only previous account of the use of BODAZ as a radical trap was by Skene et al,28 who reported a photochemical decomposition study of the corresponding 1,1‐phenylethyl alkoxyamine.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Influence of nitroxide structure on the 2,5‐ and 2,6‐spirodicyclohexyl substituted cyclic nitroxide‐mediated free‐radical polymerization of styrene

Aldabbagh

Dervan

Phelan

et al. 2003

J. Polym. Sci. A Polym. Chem.

View full text Add to dashboard Cite

The 2,6-spirodicyclohexyl substituted nitroxide, cyclohexane-1-spiro-2Ј-(3Ј,5Ј-dioxo-4Ј-benzylpiperazine-1Ј-oxyl)-6Ј-spiro-1Љ-cyclohexane (BODAZ), was investigated as a mediator for controlled/living free-radical polymerization of styrene. The values of the number-average molecular weight increased linearly with conversion, but the polydispersities were higher than for the corresponding 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) and 2,5-bis(spirocyclohexyl)-3-benzylimidazolidin-4-one-1-oxyl (NO88Bn) mediated systems at approximately 2.2 and 1.6 at 100 and 120°C, respectively. These results were reflected in the rate coefficients obtained by electron spin resonance spectroscopy; at 120°C, the values of the rate coefficients for polystyrene-BODAZ alkoxyamine dissociation (k d ), combination of BODAZ and propagating radicals (k c ), and the equilibrium constant (K) were 1.60 ϫ 10 Ϫ5 s Ϫ1 , 5.19 ϫ 10 6 M Ϫ1 s Ϫ1 , and 3.08 ϫ 10 Ϫ12 M, respectively. The value of k d was approximately one and two orders of magnitude lower, and that of K was approximately 20 and 7 times lower than for the NO88Bn and TEMPO adducts. These results are explained in terms of X-ray crystal structures of BODAZ and NO88Bn; the six-membered ring of BODAZ deviates significantly from planarity as compared to the planar five-membered ring of NO88Bn and possesses a benzyl substituent oriented away from the nitroxyl group leading to a seemingly more exposed oxyl group, which resulted in a higher k c and a lower k d than NO88Bn.

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Influence of nitroxide structure on the 2,5‐ and 2,6‐spirodicyclohexyl substituted cyclic nitroxide‐mediated free‐radical polymerization of styrene

Aldabbagh

Dervan

Phelan

et al. 2003

J. Polym. Sci. A Polym. Chem.

View full text Add to dashboard Cite

show abstract

“…It is known that oxidation of highly sterically hindered amines into nitroxides with H 2 O 2 /Na 2 WO 4 is sometimes unsuccessful and use of peracids, for example, MCPBA, gives better result. Similarly, only trace amounts of corresponding nitroxides were formed in the reaction of aminoalcohols 7a–d with hydrogen peroxide in presence of Na 2 WO 4 , while oxidation with MCPBA afforded 2a–d in 69–79% yields.…”

Section: Resultsmentioning

confidence: 97%

Controlled/living polymerization of methyl methacrylate using new sterically hindered imidazoline nitroxides prepared via intramolecular 1,3-dipolar cycloaddition reaction

Edeleva

Parkhomenko

Morozov

et al. 2013

J. Polym. Sci. Part A: Polym. Chem.

View full text Add to dashboard Cite

A series of imidazoline nitroxides with bulky spirocyclic moieties at the positions 2 or 5 of imidazole ring were synthesized using intramolecular 1,3-dipolar cycloaddition in 2Himidazole 1-oxides or 4H-imidazole 3-oxides with pent-4-enyl groups followed by isoxazolidine ring opening and oxidation. Capability of the nitroxides to control radical polymerization of methyl methacrylate (MMA) and styrene was investigated. For that purpose, alkoxyamines were synthesized from the aforementioned nitroxides and tert-butyl a-bromoisobutyrate. Homolysis rate constants of the alkoxyamines were measured and possible contributions of side reactions were quantified.Nitroxide-mediated polymerization of styrene and MMA was studied using the alkoxyamines as initiators. MMA polymerization was found to proceed in controlled regime up to 55% of monomer conversion and the polymer obtained was able to reinitiate the polymerization of styrene. Quota of "living" chains estimated to reach 90%. V C 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 929-943 Additional Supporting Information may be found in the online version of this article.

show abstract

“…Sterically hindered SNRs of the piperazine series ( 115, 116, 118 , and 120) were obtained for the first time to study the effect of substituents on hyperfine coupling constant A N in the EPR spectra of stable radicals [ 126 ]. For instance, under reduced pressure, heating the aminonitrile of cyclohexanone 111 gives bis(1-cyanocyclohexyl)amine 112 , followed by a one-pot step, including acid-catalyzed hydrolysis and intramolecular cyclization, leading to the starting compound of SNR synthesis—cyclic piperazinedione 113 [ 127 ].…”

Section: Piperazine- and Morpholine-type Snrsmentioning

confidence: 99%

Spirocyclic Nitroxides as Versatile Tools in Modern Natural Sciences: From Synthesis to Applications. Part I. Old and New Synthetic Approaches to Spirocyclic Nitroxyl Radicals

Zaytseva

Mazhukin

2021

Molecules

View full text Add to dashboard Cite

Spirocyclic nitroxyl radicals (SNRs) are stable paramagnetics bearing spiro-junction at α-, β-, or γ-carbon atom of the nitroxide fragment, which is part of the heterocyclic system. Despite the fact that the first representatives of SNRs were obtained about 50 years ago, the methodology of their synthesis and their usage in chemistry and biochemical applications have begun to develop rapidly only in the last two decades. Due to the presence of spiro-function in the SNRs molecules, the latter have increased stability to various reducing agents (including biogenic ones), while the structures of the biradicals (SNBRs) comprises a rigid spiro-fused core that fixes mutual position and orientation of nitroxide moieties that favors their use in dynamic nuclear polarization (DNP) experiments. This first review on SNRs will give a glance at various strategies for the synthesis of spiro-substituted, mono-, and bis-nitroxides on the base of six-membered (piperidine, 1,2,3,4-tetrahydroquinoline, 9,9′(10H,10H′)-spirobiacridine, piperazine, and morpholine) or five-membered (2,5-dihydro-1H-pyrrole, pyrrolidine, 2,5-dihydro-1H-imidazole, 4,5-dihydro-1H-imidazole, imidazolidine, and oxazolidine) heterocyclic cores.

show abstract

Studies on Stable Free Radicals. XIII. Synthesis and ESR Spectral Properties of Hindered Piperazine N-Oxyls

Cited by 19 publications

References 11 publications

Influence of nitroxide structure on the 2,5‐ and 2,6‐spirodicyclohexyl substituted cyclic nitroxide‐mediated free‐radical polymerization of styrene

Influence of nitroxide structure on the 2,5‐ and 2,6‐spirodicyclohexyl substituted cyclic nitroxide‐mediated free‐radical polymerization of styrene

Controlled/living polymerization of methyl methacrylate using new sterically hindered imidazoline nitroxides prepared via intramolecular 1,3-dipolar cycloaddition reaction

Spirocyclic Nitroxides as Versatile Tools in Modern Natural Sciences: From Synthesis to Applications. Part I. Old and New Synthetic Approaches to Spirocyclic Nitroxyl Radicals

Contact Info

Product

Resources

About