Sterically hindered aromatic compounds. XI. Spectral and product studies of the decomposition of <i>N</i>-nitrosoacetanilides

Barclay, L. R. C.; Dust, Julian M.

doi:10.1139/v82-090

Cited by 19 publications

(5 citation statements)

References 25 publications

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“…For the 1 + /PhNO/P 1 t Bu mixture, an EPR triplet resonance at g iso = 2.0063 with nitrogen hyperfine coupling (hfc) A ( 14 N) = 11.1 G was recorded (Figure ), similar to typical nitroxyl radicals. − Furthermore, hyperfine couplings to hydrogen nuclei of the phenyl moiety and the substituted cyclopentadienyl ring are extracted from the simulation of the EPR resonance (Table ). H o , H m , and H p denote the ortho , meta , and para protons of the phenyl substituent, respectively, while H α and H β are the alpha and beta protons of the substituted Cp ring.…”

Section: Resultsmentioning

confidence: 98%

Spin Trapping of Carbon-Centered Ferrocenyl Radicals with Nitrosobenzene

2015

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In contrast to metal centered 17 valence electron radicals, such as [Mn(CO) 5 ] • , ferrocenium ions [Fe(C 5 H 5 ) 2 ] + (1 + ), [Fe(C 5 Me 5 ) 2 ] + (2 + ), [Fe(C 5 H 5 )(C 5 H 4 Et)] + (3 + ), [Fe(C 5 H 5 )-(C 5 H 4 NHC(O)Me)] + (4 + ), and [Fe(C 5 H 5 )(C 5 H 4 NHC(S)Me)] +(5 + ) do not add to nitrosobenzene PhNO to give metal-coordinated stable nitroxyl radicals. In the presence of the strong and oxidatively stable phosphazene base tert-butylimino-tris(dimethylamino)phosphorane, the quite acidic ferrocenium ions 1 + −5 + are deprotonated to give a pool of transient and persistent radicals with different deprotonation sites• , deprotonated at the nitrogen atom, has been detected by rapid-freeze EPR spectroscopy at 77 K. This iron-centered radical• appear to rapidly abstract hydrogen atoms from the adjacent base or the solvent to regenerate the corresponding ferrocenes 1−5. These transient radicals are only present in trace amounts (<1%). However, some of the transient carbon-centered radicals in the radical pool can be trapped by 1−1.2 equiv of PhNO, even at room temperature. The corresponding resulting stable nitroxyl radicals [6] • −[10] • were studied by EPR spectroscopy at room temperature and at 77 K. The hyperfine coupling pattern to protons close to the spin center allows one to assign the site of PhNO attack in radicals [6] • −[10] • , namely, at the C 5 H 5 ring in [6] • , [9 Cp ] • , and [10 Cp ] • , at a methyl group in [7] • , and at the methylene group in [8 1 ] • . These studies give a deeper insight into the stability and reactivity of radicals derived from ferrocene derivatives which might also be relevant for the biological activity of high-potent antitumor and antimalaria ferrocene-based drugs and prodrugs such as ferrocifen or ferroquine.

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Section: Resultsmentioning

confidence: 98%

Spin Trapping of Carbon-Centered Ferrocenyl Radicals with Nitrosobenzene

2015

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“…This finding is exciting as it demonstrates for the first time that 18‐electron iron sandwich complexes spontaneously generate transient radicals. Indeed, their counterparts, the 19‐electron, and 17‐electron iron sandwich complexes are well‐known to form radicals, which account for their well‐exploited biological activity . Here, the mechanistic scenario leading to the formation of these radicals and their exact nature are yet to be understood and is a goal of a future study.…”

Section: Resultsmentioning

confidence: 99%

“…With nitrosobenzene (PhNO) as a spin trap, we found evidence for free radicals in dimethyl sulfoxide/water solution of the dendrimers. At room temperature, dendrimer/PhNO gave an EPR resonance at g iso = 2.008, which is typical of nitroxyl radicals, (Figure A). Further, characteristic of nitroxyl radicals at 77 K, the dendrimer/PhNO mixture gave an anisotropic nitrogen‐split triplet EPR resonance at g 1,2,3 = 2.010, 2.005, 1.998 (Figure B).…”

Section: Resultsmentioning

confidence: 99%

“…Indeed, their counterparts, the 19-electron, and 17-electron iron sandwich complexes are well-known to form radicals, which account for their well-exploited biological activity. [54,[63][64][65][66][67][68][69] Here, the mechanistic scenario leading to the formation of these radicals and their exact nature are yet to be understood and is a goal of a future study. Nonetheless, our finding hints a free radical-dependent biological activity for this family of dendrimers.…”

Section: Free Radical Formationmentioning

confidence: 99%

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Quaternized and Thiazole‐Functionalized Free Radical‐Generating Organometallic Dendrimers as Antimicrobial Platform against Multidrug‐Resistant Microorganisms

Abd‐El‐Aziz

Agatemor

Etkin

et al. 2017

Macromolecular Bioscience

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New macromolecules such as dendrimers are increasingly needed to drive breakthroughs in diverse areas, for example, healthcare. Here, the authors report hybrid antimicrobial dendrimers synthesized by functionalizing organometallic dendrimers with quaternary ammonium groups or 2-mercaptobenzothiazole. The functionalization tunes the glass transition temperature and antimicrobial activities of the dendrimers. Electron paramagnetic resonance spectroscopy reveals that the dendrimers form free radicals, which have significant implications for catalysis and biology. In vitro antimicrobial assays indicate that the dendrimers are potent antimicrobial agents with activity against multidrug-resistant pathogens such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium as well as other microorganisms. The functionalization increases the activity, especially in the quaternary ammonium group-functionalized dendrimers. Importantly, the activities are selective because human epidermal keratinocytes cells and BJ fibroblast cells exposed to the dendrimers are viable after 24 h.

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“…Brydon et al [5] reported the decomposition of N-nitrosoacetanilide and its derivatives in benzene. Barclay et al [6] reported the spectral and product studies of the decomposition of N-nitrosoacetanilides. The use of N-nitrosoacetanilides as NO donors in many chemical and biological reaction systems has also long been recognized [7,8].…”

Section: Introductionmentioning

confidence: 99%

Natural bond orbital analysis of some para-substituted N-nitrosoacetanilide biological molecules

Zhang

2009

Struct Chem

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Theoretical study of several para-substituted N-nitrosoacetanilide biological molecules has been performed using density functional B3LYP method with 6-31G(d,p) basis set. Geometries obtained from DFT calculation were used to perform natural bond orbital analysis. The p characters of two nitrogen natural hybrid orbital (NHO) r N3-N2 bond orbitals increase with increasing r p values of the para substituent group on the benzene, which results in a lengthening of the N 3 -N 2 bond. The p characters of oxygen NHO r O1-N2 and nitrogen NHO r O1-N2 bond orbitals decrease with increasing r p values of the para substituent group on the benzene, which results in a shortening of the N 2 =O 1 bond. It is also noted that decreased occupancy of the localized r N3-N2 orbital in the idealized Lewis structure, or increased occupancy of r Ã N3ÀN2 of the non-Lewis orbital, and their subsequent impact on molecular stability and geometry (bond lengths) are also related with the resulting p character of the corresponding nitrogen NHO of r N3-N2 bond orbital.

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Sterically hindered aromatic compounds. XI. Spectral and product studies of the decomposition of N-nitrosoacetanilides

Cited by 19 publications

References 25 publications

Spin Trapping of Carbon-Centered Ferrocenyl Radicals with Nitrosobenzene

Spin Trapping of Carbon-Centered Ferrocenyl Radicals with Nitrosobenzene

Quaternized and Thiazole‐Functionalized Free Radical‐Generating Organometallic Dendrimers as Antimicrobial Platform against Multidrug‐Resistant Microorganisms

Natural bond orbital analysis of some para-substituted N-nitrosoacetanilide biological molecules

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