- Dimethylanilinic N-Oxides and Their Oxygen Surrogacy Role in the Formation of a Putative High-Valent Copper-Oxygen Species
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The reaction of p-cyano-N,N-dimethylaniline N-oxide, an O-atom donor, with different copper(I) complexes (at room temperature and in acetone) indicates the formation via O-atom transfer of a high-valent copper oxyl species, CuII-O?, a putative key intermediate in the catalytic cycle of copper-containing monooxygenases. The formation of p-cyano-N-hydroxymethyl-N-methylaniline and p-cyano-N-methylaniline as the main products of the reaction highlight the capability of this species to hydroxylate strong C-H bonds (bond dissociation energy ~90 kcal/mol). A plausible mechanism for the reactivity of this catalytic system is proposed.
- Diaz, Daniel E.,Bhadra, Mayukh,Karlin, Kenneth D.
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p. 13746 - 13750
(2019/10/14)
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- Oxido-alcoholato/thiolato-molybdenum(VI) complexes with a dithiolene ligand generated by oxygen atom transfer to the molybdenum(IV) complexes
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Oxido-alcoholato- and oxido-thiolato-molybdenum(VI) complexes bearing two ene-1,2-dithiolate ligands (cyclohexene-1,2-dithiolate) are prepared as synthetic models of molybdenum(VI) reaction centers of dimethyl sulfoxide reductase family of molybdenum enzymes. These complexes are prepared by oxygen atom transfer from tertiary amine N-oxide (trimethylamine N-oxide and N,N-dimethylaniline N-oxide) to the five-coordinate alcoholato- and thiolato-molybdenum(IV) complexes, and are characterized by UV–vis, cold-spray-ionization mass, resonance Raman, and 1H NMR spectroscopies. The oxygen atom transfer reactions are studied kinetically at a low temperature (?40 °C) to demonstrate that the reactivity of the thiolato-molybdenum(IV) complex is higher than that of alcoholato-molybdenum(IV) complex by about 7 times, and that the oxygen atom transfer reactivity increases with increasing the electron withdrawing ability of the p-substituent of N,N-dimethylaniline N-oxide derivatives. Mechanistic details are discussed based on the reactivity studies.
- Sugimoto, Hideki,Sato, Masanori,Asano, Kaoru,Suzuki, Takeyuki,Ogura, Takashi,Itoh, Shinobu
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- Synthesis of Halogenated Anilines by Treatment of N, N-Dialkylaniline N-Oxides with Thionyl Halides
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The special reactivity of N,N-dialkylaniline N-oxides allows practical and convenient access to electron-rich aryl halides. A complementary pair of reaction protocols allow for the selective para-bromination or ortho-chlorination of N,N-dialkylanilines in up to 69% isolated yield. The generation of a diverse array of halogenated anilines is made possible by a temporary oxidation level increase of N,N-dialkylanilines to the corresponding N,N-dialkylaniline N-oxides and the excision of the resultant weak N-O bond via treatment with thionyl bromide or thionyl chloride at low temperature.
- Reed, Hayley,Paul, Tyler R.,Chain, William J.
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p. 11359 - 11368
(2018/08/06)
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- Oxovanadium(IV)-salen ion catalyzed H2O2 oxidation of tertiary amines to n-oxides- critical role of acetate ion as external axial ligand
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The oxovanadium(IV)-salen ion catalyzed H2O2 oxidation of N,N-dimethylaniline forms N-oxide as the product of the reaction. The reaction follows Michaelis-Menten kinetics and the rate of the reaction is accelerated by electron donating groups present in the substrate as well as in the salen ligand. This peculiar substituent effect is accounted for in terms of rate determining bond formation between peroxo bond of the oxidant and the N-atom of the substrate in the transition state. Trichloroacetic acid (TCA) shifts the λmax value of the oxidant to the red region and catalyzes reaction enormously. The cleavage of N£O bond by vanadium complex leads to moderate yield of the product. But the percentage yield of the product becomes excellent in the presence of TCA.
- Mathavan, Alagarsamy,Ramdass, Arumugam,Ramachandran, Mohanraj,Rajagopal, Seenivasan
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supporting information
p. 315 - 326
(2015/04/14)
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- Catalytic N-oxidation of tertiary amines on RuO2NPs anchored graphene nanoplatelets
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Ultrafine ruthenium oxide nanoparticles (RuO2NPs) with an average diameter of 1.3 nm were anchored on graphene nanoplatelets (GNPs) using a Ru(acac)3 precursor by a very simple dry synthesis method. The resultant material (GNPs-RuO2NPs) was used as a heterogeneous catalyst for the N-oxidation of tertiary amines for the first time. The transmission electron microscopy (TEM) images of the GNPs-RuO2NPs showed the excellent attachment of RuO2NPs on GNPs. The loading of Ru in GNPs-RuO2NPs was 2.68 wt%, as confirmed by scanning electron microscope-energy dispersive spectroscopy (SEM-EDS). The X-ray photoelectron spectrum (XPS) and the X-ray diffraction pattern (XRD) of GNPs-RuO 2NPs revealed that the chemical state of Ru on GNPs was +4. After the optimization of reaction conditions for N-oxidation of triethylamine, the scope of the reaction was extended to various aliphatic, alicyclic and aromatic tertiary amines. The GNPs-RuO2NPs showed excellent catalytic activity in terms of yields even at a very low amount of Ru catalyst (0.13 mol%). The GNPs-RuO2NPs was heterogeneous in nature, chemically as well as physically, very stable and could be reused up to 5 times. The Royal Society of Chemistry 2014.
- Gopiraman, Mayakrishnan,Bang, Hyunsik,Babu, Sundaram Ganesh,Wei, Kai,Karvembu, Ramasamy,Kim, Ick Soo
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p. 2099 - 2106
(2014/06/24)
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- Anilinic N-oxides support cytochrome P450-mediated N-dealkylation through hydrogen-atom transfer
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The mechanism of N-dealkylation mediated by cytochrome P450 (P450) has long been studied and argued as either a single electron transfer (SET) or a hydrogen atom transfer (HAT) from the amine to the oxidant of the P450, the reputed iron-oxene. In our study, tertiary anilinic N-oxides were used as oxygen surrogates to directly generate a P450-mediated oxidant that is capable of N-dealkylating the dimethylaniline derived from oxygen donation. These surrogates were employed to probe the generated reactive oxygen species and the subsequent mechanism of N-dealkylation to distinguish between the HAT and SET mechanisms. In addition to the expected N-demethylation of the product aniline, 2,3,4,5,6-pentafluoro-N,N-dimethylaniline N-oxide (PFDMAO) was found to be capable of N-dealkylating both N,N-dimethylaniline (DMA) and N-cyclopropyl-N-methylaniline (CPMA). Rate comparisons of the N-demethylation of DMA supported by PFDMAO show a 27-fold faster rate than when supported by N,N-dimethylaniline N-oxide (DMAO). Whereas intermolecular kinetic isotope effects were masked, intramolecular measurements showed values reflective of those seen previously in DMAO- and the native NADPH/O2-supported systems (2.33 and 2.8 for the N-demethylation of PFDMA and DMA from the PFDMAO system, respectively). PFDMAO-supported N-dealkylation of CPMA led to the ring-intact product N-cyclopropylaniline (CPA), similar to that seen with the native system. The formation of CPA argues against a SET mechanism in favor of a P450-like HAT mechanism. We suggest that the similarity of KIEs, in addition to the formation of the ring-intact CPA, argues for a similar mechanism of Compound I (Cpd I) formation followed by HAT for N-dealkylation by the native and N-oxide-supported systems and demonstrate the ability of the N-oxide-generated oxidant to act as an accurate mimic of the native P450 oxidant.
- Roberts, Kenneth M.,Jones, Jeffery P.
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experimental part
p. 8096 - 8107
(2010/09/11)
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- Probing the reactivity of oxomanganese-salen complexes: An electrospray tandem mass spectrometric study of highly reactive intermediates
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Electrospray ionization in combination with tandem mass spectrometric techniques has been employed to study the formation of oxomanganese-salen complexes upon oxidation of [MnIII(salen)]+ cations as well as the properties and reactions of the oxidized species in the gas phase. Two species could be characterized as the principal oxidation products: the oxomanganese(V) complex, [Mn=O(salen)]+, which is the actual oxygen-transfer agent in epoxidation reactions, and the dinuclear, μ-oxo bridged [L(salen)Mn-Q-Mn-(salen)L]2+ with two terminal ligands L; the latter acts as a reservoir species. The effects of various substituents in the 5-and 5′-positions, respectively, of the salen ligand on the reactivity of the epoxidation catalyst were determined quantitatively from CID (collision-induced dissociation) experiments and B3LYP density functional calculations. Accordingly, the effect of axial donor ligands on the reactivity of the epoxidation catalyst was studied. Electron-withdrawing substitutents on the salen ligand and additional axial ligands decrease the stability and thus enhance the reactivity of the Mn=O moiety, while electron-donating salen substituents have a strong stabilizing effect. WILEY-VCH Verlag GmbH, 2001.
- Feichtinger, Derek,Plattner, Dietmar A.
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p. 591 - 599
(2007/10/03)
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