scholarly journals RuO4-mediated oxidation of N-benzylated tertiary amines. 3. Behavior of 1,4-dibenzylpiperazine and its oxygenated derivatives

2006 ◽  
Vol 4 (4) ◽  
pp. 674-694 ◽  
Author(s):  
Horia Petride ◽  
Constantin Drăghici ◽  
Cristina Florea ◽  
Aurica Petride
Keyword(s):  
Benzoic Acid ◽  
Oxidation Reaction ◽  
Oxidation Mechanism ◽  
Tertiary Amines ◽  
Reaction Conditions ◽  
Iminium Cations ◽  
Work Up ◽  
Hydrolysis Of ◽  
Mediated Oxidation

Abstract1,4-Dibenzylpiperazine (1),-2-piperazinone (7),-2,6-piperazinedione (9), and 1-benzoyl-4-benzylpiperazine (30) were oxidized by RuO4 (generated in situ) by attack at their endocyclic and exocyclic (i.e., benzylic) aminic N-α-C-H bonds to afford various oxygenated derivatives, including acyclic diformamides, benzaldehyde, and benzoic acid. The reaction outcome was complicated by (i) the hydrolysis of diformamides, occurred during the work-up, and (ii) the reaction of benzaldehyde with the hydrolysis-derived amines giving imidazolidines and/or Schiff bases. Benzoic acid resulted from benzaldehyde only. Compounds 7, 30, and 1-benzylpiperazine, but not 9, were transiently formed during the oxidation of 1. In the same reaction conditions, 1,4-dibenzyl-2,3-(or 2,5)-piperazinedione, 1,4-dibenzyl-2,3,6-piperazinetrione, 4-benzyol-1-benzyl-2-piperazinone, and 1,4-dibenzoylpiperazine were inert. The proposed oxidation mechanism involves the formation of endocyclic and exocyclic iminium cations, as well as of cyclic enamines. The latter intermediates probably result by base-induced deprotonation of the iminium cations, provided an N +−β-proton is available. In the case of 1, the cations were trapped with NaCN as the corresponding α-aminonitriles. The statistically corrected regioselectivity (endocyclic/exocyclic) of the RuO4-induced oxidation reaction of 1, 7, and 30 was 1.2–1.3.

scholarly journals RuO4-mediated oxidation ofN-benzylated tertiary amines. Are amineN-oxides and iminium cations reaction intermediates?

2004 ◽  
Vol 2 (2) ◽  
pp. 302-322 ◽  
Author(s):  
Horia Petride ◽  
Constantin Drãghici ◽  
Cristina Florea ◽  
Aurica Petride
Keyword(s):  
Oxidation Reaction ◽  
Cation Radical ◽  
Side Reaction ◽  
Oxidation Products ◽  
Reaction Intermediates ◽  
Tertiary Amines ◽  
Iminium Cations ◽  
Carbon Centered Radical ◽  
A Minor ◽  
Mediated Oxidation

AbstractN-Benzylmorpholine,-piperidine, and-pyrrolidine (1A-C, resp.) are oxidised by RuO4 (generatedin situ) at both endocyclic and exocyclic (benzylic)N—α-methylene positions to afford lactams (and dioxo-derivatives) and benzaldehyde (and benzoyl derivatives), respectively. TheN-oxides of1A-C, formed by a minor side reaction, are not involved as intermediates. Control experiments showed the transient formation of endo- and exocyclic iminium cations trapped with NaCN as the corresponding nitriles. The proposed course of the RuO4-mediated oxidation of1A-C involves the consecutive steps1⇒iminium cations+cyclic enamine⇒oxidation products. The endocyclic/exocyclic regioselectivity of the oxidation reaction lies between 0.8 (for1A) and 2.1 (for1B). The amine cation radical and theN-α-C· carbon-centered radical seem not to be involved.

scholarly journals Facile Synthesis of Pd@PtM (M = Rh, Ni, Pd, Cu) Multimetallic Nanorings as Efficient Catalysts for Ethanol Oxidation Reaction

2021 ◽  
Vol 9 ◽  
Author(s):  
Xingqiao Wu ◽  
Xiao Li ◽  
Yucong Yan ◽  
Sai Luo ◽  
Jingbo Huang ◽  
...  
Keyword(s):  
Benzoic Acid ◽  
Epitaxial Growth ◽  
Oxidation Reaction ◽  
Ethanol Oxidation ◽  
Hollow Structure ◽  
Ethanol Oxidation Reaction ◽  
Hollow Nanostructures ◽  
Oxidative Etching ◽  
General Method

Pt-based multimetallic nanorings with a hollow structure are attractive as advanced catalysts due to their fantastic structure feature. However, the general method for the synthesis of such unique nanostructures is still lack. Here we report the synthesis of Pd@PtM (M = Rh, Ni, Pd, Cu) multimetallic nanorings by selective epitaxial growth of Pt alloyed shells on the periphery of Pd nanoplates in combination with oxidative etching of partial Pd in the interior. In situ generation of CO and benzoic acid arising from interfacial catalytic reactions between Pd nanoplates and benzaldehyde are critical to achieve high-quality Pt-based multimetallic nanorings. Specifically, the in-situ generated CO promotes the formation of Pt alloyed shells and their epitaxial growth on Pd nanoplates. In addition, the as-formed benzoic acid and residual oxygen are responsible for selective oxidative etching of partial Pd in the interior. When evaluated as electrocatalysts, the Pd@PtRh nanorings exhibit remarkably enhanced activity and stability for ethanol oxidation reaction (EOR) compared to the Pd@PtRh nanoplates and commercial Pt/C due to their hollow nanostructures.

scholarly journals CO Oxidation on Stepped Rh Surfaces: μm-Scale Versus Nanoscale

2019 ◽  
Vol 150 (3) ◽  
pp. 605-612 ◽  
Author(s):  
Y. Suchorski ◽  
I. Bespalov ◽  
J. Zeininger ◽  
M. Raab ◽  
M. Datler ◽  
...  
Keyword(s):  
Co Oxidation ◽  
Oxidation Reaction ◽  
Active Surface ◽  
Reaction Conditions ◽  
Miller Index ◽  
Co Oxidation Reaction ◽  
Catalytically Active ◽  
Field Emission Microscopy ◽  
Photoemission Electron

Abstract The catalytic CO oxidation reaction on stepped Rh surfaces in the 10−6 mbar pressure range was studied in situ on individual μm-sized high-Miller-index domains of a polycrystalline Rh foil and on nm-sized facets of a Rh tip, employing photoemission electron microscopy (PEEM) and field-ion/field-emission microscopy (FIM/FEM), respectively. Such approach permits a direct comparison of the reaction kinetics for crystallographically different regions under identical reaction conditions. The catalytic activity of the different Rh surfaces, particularly their tolerance towards poisoning by CO, was found to be strongly dependent on the density of steps and defects, as well as on the size (µm vs. nm) of the respective catalytically active surface. Graphic Abstract

Synthesis of substituted phenols by directed ortho-lithiation of in situ N-silyl-protected O-aryl N-monoalkylcarbamates

2001 ◽  
Vol 79 (11) ◽  
pp. 1736-1746 ◽  
Author(s):  
Matthias Kauch ◽  
Dieter Hoppe
Keyword(s):  
High Yield ◽  
Substituted Phenols ◽  
Cleavage Reaction ◽  
Reaction Conditions ◽  
Fries Rearrangement ◽  
Silyl Group ◽  
Ortho Metalation ◽  
Electrophilic Reagents ◽  
Work Up

A simple, high-yield procedure has been developed for the ortho-lithiation and subsequent ortho-substitution of phenols by a manifold of electrophiles. N,C-Dilithiation of O-aryl N-monoalkylcarbamates proved to be impossible due to a cleavage reaction of the monolithiated intermediates. However, in situ N-silylation of O-aryl N-isopropylcarbamates proceeds smoothly with trialkylsilyl triflates – N,N,N',N'-tetramethylethylenediamine (TMEDA). Separation of the formed O-aryl N-isopropyl-N-trialkylsilylcarbamates from the byproduct TMEDA·HOTf, which is insoluble in diethyl ether or toluene, is not required. ortho-Lithiation with n-butyllithium–TMEDA at –78°C leads to the corresponding aryllithium, which does not undergo anionic ortho-Fries rearrangement under the reaction conditions, but is efficiently substituted by electrophilic reagents. During the aqueous work-up, the N-silyl group is removed and the corresponding ortho-substituted O-aryl N-isopropylcarbamate is isolated. Among the introduced electrophiles are: Me3Si, Bu3Sn, PhS, I, Br, Cl, alkyl, α-hydroxyalkyl. Liberation of the free phenols is performed under mild alkaline conditions.Key words: directed ortho-metalation, ortho-lithiated O-aryl carbamates, ortho-substituted phenols, in situ protection of N-monoalkylcarbamates.

Acid-induced intermolecular [3+2] cycloaddition/oxidation to synthesize polysubstituted benzo[f]isoindole-4,9-diones

2019 ◽  
Vol 43 (9-10) ◽  
pp. 359-366 ◽  
Author(s):  
Zhang-qi Lin ◽  
Chao-dong Li ◽  
Yu-jin Li ◽  
Yong-jian Zhang ◽  
Zi-chun Zhou ◽  
...  
Keyword(s):  
Benzoic Acid ◽  
Oxidation Reaction ◽  
Aromatic Aldehydes ◽  
Dipolar Cycloaddition ◽  
Reaction Conditions ◽  
One Pot ◽  
Amino Esters ◽  
Wide Range

A novel one-pot 1,3-dipolar cycloaddition/oxidation reaction of 1,4-quinones, aromatic aldehydes, and N-substituted amino esters to construct polysubstituted benzo[ f]isoindole-4,9-diones induced by benzoic acid is reported. Based on optimized reaction conditions, various polysubstituted benzo[ f]isoindole-4,9-diones derivatives are obtained in moderate yields. This straightforward methodology employs mild reaction conditions, a green oxidant, and readily available starting materials. Notably, a wide range of substrates is tolerated.

One-Pot Catalytic Epoxidation Reaction of Perfluoro-2-methyl-2-pentene with Tri-n-butylamine N-Oxide or N, N-Dimethylcyclohexylamine N-Oxide

2013 ◽  
Vol 685 ◽  
pp. 357-361 ◽  
Author(s):  
Min Sha ◽  
Ren Ming Pan ◽  
Biao Jiang
Keyword(s):  
Organic Chemistry ◽  
Hydrogen Peroxide ◽  
Low Cost ◽  
Reaction Conditions ◽  
One Pot ◽  
Catalytic Epoxidation ◽  
Epoxidation Reaction ◽  
Work Up ◽  
Better Than

Perfluoro epoxy compounds are important intermediates in organic chemistry, however, the methods for preparing them are scanty. We found that in situ generated tri-n-butylamine N-oxide and N,N-Dimethylcyclohexylamine N-oxide were found to be good reagents for the epoxidation of tri-substituted Perfluoro-2-methyl-2-pentene in good to excellent yields. Catalytic epoxidation methods were developed by coupling this reaction with the N-oxidation of tertiary amine by hydrogen peroxide or MCPBA. The advantages of these methods are easy work-up, mild reaction conditions, environmentally friendly and low cost. The reaction using MCPBA as a oxidant is better than hydrogen peroxide for it is fast and high yielding.

scholarly journals The Ca2+-Binding Capacity of Epidermal Furin Is Disrupted by H2O2-Mediated Oxidation in Vitiligo

Endocrinology ◽  
2008 ◽  
Vol 149 (4) ◽  
pp. 1638-1645 ◽  
Author(s):  
J. D. Spencer ◽  
N. C. J. Gibbons ◽  
M. Böhm ◽  
K. U. Schallreuter
Keyword(s):  
Computer Simulation ◽  
Binding Sites ◽  
Binding Capacity ◽  
Oxidation Mechanism ◽  
Epidermal Keratinocytes ◽  
Rt Pcr ◽  
Binding Studies ◽  
Epidermal Expression ◽  
Mediated Oxidation

The Ca2+-dependent precursor convertase furin is abundantly expressed in epidermal keratinocytes and melanocytes. In this context, it is noteworthy that proopiomelanocortin (POMC) cleavage is also processed by furin, leading to ACTH, β-lipotropin, and β-endorphin. All prohormone convertases including furin are regulated by Ca2+. Because numerous epidermal peptides and enzymes are affected by H2O2-mediated oxidation, including the POMC-derived peptides α-MSH and β-endorphin as shown in the epidermis of patients with vitiligo, we here asked the question of whether furin could also be a possible target for this oxidation mechanism by using immunofluorescence, RT-PCR, Western blotting, Ca2+-binding studies, and computer modeling. Our results demonstrate significantly decreased in situ immunoreactivity of furin in the epidermis of patients with progressive vitiligo (n = 10), suggesting H2O2-mediated oxidation. This was confirmed by 45Ca2+-binding studies with human recombinant furin identifying the loss of one Ca2+-binding site from the enzyme after oxidation with H2O2. Computer simulation supported alteration of one of the two Ca2+-binding sites on furin. Taken together, our results implicate that the Ca2+-dependent proteolytic activity of this convertase is targeted by H2O2, which in turn could contribute to the reduced epidermal expression of the POMC-derived peptides α-MSH and β-endorphin as documented earlier in patients with vitiligo.

scholarly journals A Brønsted Acid-Catalyzed Multicomponent Reaction for the Synthesis of Highly Functionalized γ-Lactam Derivatives

Molecules ◽  
2019 ◽  
Vol 24 (16) ◽  
pp. 2951 ◽  
Author(s):  
Corte ◽  
Marigorta ◽  
Palacios ◽  
Vicario
Keyword(s):  
Phosphoric Acid ◽  
Multicomponent Reaction ◽  
Mannich Reaction ◽  
Acid Catalyst ◽  
Selective Hydrolysis ◽  
Reaction Conditions ◽  
Amide Derivatives ◽  
Acid Catalyzed ◽  
Hydrolysis Of

Brønsted acids catalyze a multicomponent reaction of benzaldehyde with amines and diethyl acetylenedicarboxylate to afford highly functionalized γ-lactam derivatives. The reaction consists of a Mannich reaction of an enamine to an imine, both generated in situ, promoted by a phosphoric acid catalyst and a subsequent intramolecular cyclization. The hydrolysis of the cyclic enamine substrate can provide enol derivatives and, moreover, a second attack of the amine on the carboxylate can afford amide derivatives. An optimization of the reaction conditions is presented in order to obtain selectively cyclic enamines that can afford the enol species after selective hydrolysis.

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