Phenyldiazonium Salts Research Articles

Electrochemistry and Reactivity of Surface-Confined Catechol Groups Derived from Diazonium Reduction. Bias-Assisted Michael Addition at the Solid/Liquid Interface

We have designed a novel catechol-modified electrode that could be used for bias-assisted Michael addition at the solid/liquid interface. The glassy carbon electrode was modified by the electrochemical reduction of a catechol para-substituted phenyldiazonium salt. The electrochemistry of surface-confined catechol moieties was investigated by cyclic voltammetry. The transfer coefficient and apparent surface standard electron-transfer rate constant were obtained using Laviron's theory. We demonstrate that o-quinone moieties linked to the surface remain quite reactive with nucleophilic species by Michael addition at the solid/liquid interface. To demonstrate the versatility of this procedure, 4-nitrobenzyl alcohol, (4-nitrobenzyl)amine, and a ferrocenealkylamine were chosen as nucleophile models due to their well-known redox properties. Electrochemically triggered Michael addition was validated, leading to redox headgroup-tethered surfaces.

XPS study of ruthenium tris-bipyridine electrografted from diazonium salt derivative on microcrystalline boron doped diamond

Boron doped diamond (BDD) functionalization has received an increasing interest during the last few years. Such an infatuation comes from the original properties of BDD, including chemical stability or an electrochemical window, that opens the way for the design of (bio)sensors or smart interfaces. In such a context, diazonium salts appear to be well suited for BDD functionalization as they enable covalent immobilization of functional entities such as enzymes or DNA. In this study we report microcrystalline BDD functionalization with a metallic complex, ruthenium tris(bipyridine), using the p-(tris(bipyridine)Ru(2+))phenyl diazonium salt. Electrografting using cyclic voltammetry (CV) allowed the formation of a ruthenium complex film that was finely characterized using electrochemistry and X-ray photoelectron spectroscopy (XPS). Moreover, we showed that chronopotentiometry (CP) is a convenient tool to monitor Ru complex film deposition through the control of the electrochemical pulse parameters (i.e. current density and pulse duration). Finally, such a control was demonstrated through the correlation between electrochemical and XPS characterizations.

EIS study of the redox reaction of [formula omitted] at glassy carbon electrode via diazonium reduction in aqueous and acetonitrile solutions

The derivatization of a glassy carbon electrode surface was achieved by electrochemical reduction of two phenyl diazonium salts in aqueous and acetonitrile solutions. The effect of diazonium thin films at the surface of a glassy carbon electrode on their electrochemical responses in the presence of Fe ( CN ) 6 3 - / 4 - probe have been investigated. The substituted phenyl layers are much more compact and less permeable in a nonaqueous solvent than with an aqueous solvent. Electrochemical impedance measurements indicate that the kinetics of electron transfer is showed down when the time and the concentration used to modify the glassy carbon electrode are increased. Also, electron transfer processes of Fe ( CN ) 6 3 - / 4 - in solutions of various pHs at the modified electrode are studied. Changing the solution pH would result in the terminal group’s charge state, based on which the surface p K a values are estimated.

Modification of carbon electrode in ionic liquid through the reduction of phenyl diazonium salt. Electrochemical evidence in ionic liquid

Electrochemical reduction of the 4-nitrophenyl diazonium salt in ionic liquid media has been investigated at carbon electrode. The ionic liquid chosen for this study was 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMIM][TFSI]. The cyclic voltammetry study demonstrated the possibility of the electrochemical grafting of the nitrophenyl groups onto carbon electrode after the reduction of its corresponding diazonium in ionic liquid. The electrochemical characterization of the modified electrode achieved on ionic liquid displays the presence of the nitrophenyl group at the carbon surface. Moreover, the surface concentration of the attached group obtained in this media was found to be around 1.7 × 10 −10 mol cm −2, this value may suggest the possibility of the formation of monolayer. Furthermore, the characterization of the modified electrode in [EMIM][TFSI] showed the conversion of some NO 2-phenyl groups to NHOH-phenyl. This observation could indicate the presence of surface interaction between the reduced NO 2-phenyl and the ionic liquid cation, thanks to the presence of acidic proton in the ionic liquid cation.

The modification of glassy carbon and gold electrodes with aryl diazonium salt: The impact of the electrode materials on the rate of heterogeneous electron transfer

The heterogeneous electron-transfer properties of ferrocenemethylamine coupled to a series of mixed 4-carboxyphenyl/phenyl monolayers on glassy carbon (GC) and gold electrodes were investigated, by cyclic voltammetry, in aqueous buffer solutions. The electrodes were derivatized in a step-wise process. Electrochemical reduction of mixtures of 4-carboxyphenyl and phenyl diazonium salts on the electrode surfaces yielded stable monolayers. The introduction of carboxylic acid moieties onto the surfaces was verified by X-ray photoelectron spectroscopy. Subsequently the 4-carboxyphenyl moieties were activated using water-soluble carbodiimide and N-hydroxysuccinimide and reacted with ferrocenemethylamine. The rate constants of electron transfer through the monolayer systems were determined from cyclic voltammograms using the Marcus theory for electron transfer and were found to be an order of magnitude higher for the ferrocene-modified monolayer systems on gold than those on GC electrodes. The results suggest the electrode material has an important influence on the rate of electron transfer.

One-Pot Four-Component Reaction: Aqueous TiCl3/PhN2+-Mediated Alkyl Radical Addition to Imines Generated in Situ

Ti(III)-induced free-radical decomposition of a phenyldiazonium salt, followed by phenyl radical iodine-atom abstraction from alkyl iodides, leads to a one-pot selective alkyl radical addition to the C-atom of imines generated in situ under aqueous acidic conditions. [reaction: see text]

Interaction of oxidative bleach containing detergents with dyes. Part 1: Preparation and resistance of 1-amino-2-arylazonaphthalene-4-sulphonic acid dyes to hydrogen peroxide and m-chloroperbenzoic acid

A series of red water soluble azo dyes were prepared by coupling variously substituted phenyldiazonium salts onto 1-aminonaphthalene-4-sulphonic acid. In order to mimic the conditions experienced during domestic laundering, in presence of an oxidative-bleach containing detergent, the dyes were then subjected, separately, to treatment with m-chloroperbenzoic acid and with hydrogen peroxide. Experiments were conducted under alkaline conditions (pH 9.8) and pseudo first order rate constants were determined for dye destruction. The m-chloroperbenzoic acid was much more effective than hydrogen peroxide in bringing about loss of colour. The introduction of electron donating groups into the diazo component of the dyestuff, which would be expected to lead to an increased propensity to undergo attack by electrophilic species, resulted in increased levels of bleaching by the peracid. Additionally reduction in pH caused an increase in the rate of bleaching in presence of peracid, the rate increasing approximately tenfold per unit drop in pH. These observations are consistent with attack by m-chloroperbenzoic acid, a highly electrophilic species, rather than m-chloroperbenzoate (the major species present at pH 9.8).

Addition curable phenolic resins based on ethynyl phenyl azo functional novolac

Novel addition curable phenolic resins bearing terminal ethynyl groups anchored to benzene ring through a phenyl azo linkage were realized by the coupling reaction between novolac and 3-ethynyl phenyl diazonium salt. The diazo-coupling occurred to a maximum of 50 mol%. The apparent molecular weight, determined from gel permeation chromatography showed a downward drift with increase in degree of acetylene substitution. The resin underwent curing in a broad temperature range 140–240 °C. Analyses using a model compound indicate that the curing occurs via various addition polymerization of acetylene groups. The thermal stability and anaerobic char yield of the polymers increased proportional to the crosslinking and were considerably superior to those of a conventional resole. Isothermal pyrolysis studies implied the possibility for the decomposition occurring mainly by loss of nitrogen gas, and hydrocarbon to form mostly an amorphous char.

Aza-analogs of 8-styrylxanthines as A2A-adenosine receptor antagonists.

In the present study we synthesized aza-analogs of 8-styrylxanthines, in which the ethenyl bridge is replaced by an imine, amide, or azo function, in order to investigate structure-activity relationships of the 8-substituent of A2A-selective xanthine derivatives. Thus, various 8-substituents were combined with theophylline or caffeine, respectively, and affinities of the novel compounds for adenosine A1- and A2a-receptors were determined and compared with those of analogous 8-styrylxanthine derivatives. 8-(Benzylideneamino)caffeine derivatives exhibited high affinity and selectivity for A2A-adenosine receptors, but were unstable in aqueous buffer solution at physiological pH values. 8-(Phenylazo)caffeine derivatives were less potent than corresponding 8-styrylcaffeine derivatives at adenosine receptors. The most potent azo compound of the present series was 8-(m-chlorophenylazo)caffeine (14b) exhibiting a Ki value of 400 nM at A2A-adenosine receptors and 20-fold selectivity versus A1-receptors. Due to the facile synthetic access to 8-(phenylazo)xanthine derivatives, which are obtained by coupling of 8-unsubstituted xanthines with phenyldiazonium salts, 14b may be an interesting new lead compound for the development of more potent and selective A2A-antagonists with azo structure.

Fluoro-containing oxosulfonium ylides-derivatives of alkylsulfonyl fluorides and alkylperfluoroalkylsulfones aci-form

Recent results of a systematic study of a new reaction-pyrolysis of phenyldiazonium salts stabilized by the anions of strong and superstrong CH-acids H n C(SO 2R F) − 3− n , R FF, Alk F, are discussed ▪ The reaction is due to the phenyl cation attack to the O-atom of one fluoro-containing sulfonyl group of the C-anion. Chemical properties and structure peculiarities of the novel oxosulfonium ylides will be presented.

Synthesis and reactions of 2-amino-1-aryl-5-oxo-?2-pyrroline-3-carbonitriles

The reaction of malononitrile with α-chloro acetanilides1 in presence of potassium carbonate yields the 1-aryl-5-oxo-Δ2-pyrrolin-3-carbonitriles2, in presence of triethylamine the 4,6-diamino-1-aryl-2-oxo-2,3-dihydropyrrolo[2,3-b]pyridin-5-carbonitriles3 are formed. From 2-chloroacetylamino-benzencarbonitrile and malononitrile the 5-amino-1-oxo-1,2-dihydropyrrolo[1,2-a]chinazolin-3-carbonitrile (4) arise. Analogously from the 2-chloroacetylamino-thiophen-3-carbonitries5 the 7,8-dihydro-thieno[3,2-e]pyrrolo[1,2-a]pyrimidine derivatives6 are obtainable. Hydrolysis of2 a by treatment with hydroxide or acid, respectively, yields the 1,1,2-ethanetricarboxylic acid and derivatives9 a,b. Phenyldiazonium salt reacts with2 to form the triazene 7 only.

ChemInform Abstract: Synthesis and Structure of α‐Diketone Monophenylhydrazones in the Pyrimidine Series.

AbstractThe monohydrazones of phenylpyrimidinylglyoxals (III) are obtained from the phenacylpyrimidines (I) and a phenyldiazonium salt (II) in alkaline solution.

Reaction of 4-chlorobenzenediazonium chloride with L-proline, sarcosine, and DL-alanine

The rates of reactions of substituted phenyldiazonium salts with the title amino acids were estimated in the pH range 6.5-10.5. The reaction product of 4-chlorobenzenediazonium chloride and L-proline was isolated and its triazene structure was shown.

ChemInform Abstract: SYNTHESIS OF SOME NEWER FORMAZANS AND TETRAZOLIUM SALTS AND THEIR EFFECT ON RANIKHET DISEASE VIRUS AND THE VACCINIA VIRUS

AbstractDie Hydrazone (I) bzw. (IV) wurden mit Ary1diazonium‐Salzen (II) zu den Formazanen (III) bzw. (V) umgesetzt.

Synthesis of some new formazans as potential antiviral agents.

AbstractFifteen new formazans were synthesized by the condensation of the 4‐nitrophenylhydrazone of 3‐nitro‐anisaldehyde with the appropriate phenyldiazonium salts. Their in vivo antiviral activity was evaluated against Ranikhet disease virus (RDV) in chick embryos. Out of the compounds screened, 1‐[4′‐carboxyphenyl]‐3‐[3‐nitro‐4‐methoxyphenyl]‐5‐[4‐nitrophenyl]formazan (8) showed maximum (62.5%) protection against RDV. The structure activity relationship has further been studied and is discussed.

Synthesis of 2-hydroxy-3-carbethoxy-5,6-dialkylpyrazines

Some 2-hydroxy-3-carbethoxy-5,6-dialkylpyrazines were synthesized by reacting the hydrochlorides of α-amino ketones with carbethoxyacetyl chloride in the presence of N,N-di-ethylaniline, azo-coupling the obtained N-(carbethoxyacetyl)-α-amino ketones with phenyldiazonium salt, and reduction of the intermediate N-(phenylhydrazonocarbethoxyacetyl)-α-amino ketones with zinc.

ChemInform Abstract: SYNTHESIS OF 2‐HYDROXY‐3‐CARBETHOXY‐5,6‐DIALKYLPYRAZINES

Some 2-hydroxy-3-carbethoxy-5,6-dialkylpyrazines were synthesized by reacting the hydrochlorides of α-amino ketones with carbethoxyacetyl chloride in the presence of N,N-di-ethylaniline, azo-coupling the obtained N-(carbethoxyacetyl)-α-amino ketones with phenyldiazonium salt, and reduction of the intermediate N-(phenylhydrazonocarbethoxyacetyl)-α-amino ketones with zinc.

ChemInform Abstract: SYNTHESIS OF SOME NEWER FORMAZANS AND TETRAZOLIUM SALTS AS ANTIVIRAL AGENTS

AbstractAus dem Aldehyd (I) werden mit Phenylhydrazin (II) das Hydrazon (III) und hieraus durch Umsetzung mit Diazoniumsalzen (IV) die Formazane (V) hergestellt.

Synthesis of 2-hydroxy-3-carbethoxy-5,6-dialkylpyrazines

Some 2-hydroxy-3-carbethoxy-5,6-dialkylpyrazines were synthesized by reacting the hydrochlorides of α-amino ketones with carbethoxyacetyl chloride in the presence of N,N-di-ethylaniline, azo-coupling the obtained N-(carbethoxyacetyl)-α-amino ketones with phenyldiazonium salt, and reduction of the intermediate N-(phenylhydrazonocarbethoxyacetyl)-α-amino ketones with zinc.

Azobilirubin isomers: NMR structure determination using a shift reagent

AbstractThe isomeric benzeneazodipyrromethene derivatives, obtained from the reaction of bilirubin and a phenyldiazonium salt were separated as their corresponding methyl esters. The lanthanide‐induced chemical shifts, coupling constants and double irradiation experiments permit direct assignment of methyl and vinyl substituent positions in these bilirubin‐derived isomers.