Azo Coupling Products Research Articles

Synthesis novel pigments by the α-phenylhydrazation of 2-ketomethylquinoline derivatives

Azo dyes with the general formula X–N N–Y are well known to be important dyestuffs. Dyes with a hydroxy group are known to exhibit an azo–hydrazone tautomerism and NMR measurements are well suited to investigate this type of tautomerism. In particular multinuclear studies form the basis of a powerful investigation technique. The azo-coupling products have been prepared from derivatives of 2-ketomethylquinoline and aryldiazonium ions. Structure of the products obtained was studied by means of multinuclear NMR spectroscopy in CDCl 3 solution, IR and Mass spectroscopy. Products are only present as hydrazone forms in both the solution and the solid state.

Solution and solid state structure and tautomerism of azo coupled enaminone derivatives of benzoylacetone

The reaction of 4-substituted benzenediazonium tetrafluoroborates with 3-amino-1-phenylbut-2-en-1-one, 4-amino-4-phenylbut-3-en-2-one and their N-aryl derivatives 1a-1g has been used to prepare the respective azo coupling products i.e. compounds 2-5 from enaminone 1a, compounds 6-9 from enaminone 1c, compound 10 from enaminone 1d, compound 11 from enaminone 1e, compounds 12, 13 from enaminone 1f, compounds 14, 15 from enaminone 1b and compound 16 from enaminone 1g. Tautomerism of the azo coupling products prepared has been investigated in CDCl3 solutions by means of 1H, 13C and 15N NMR spectra. Crystal structures of selected products have also been investigated by means of X-ray diffraction.

Divalent transition metal complexes

4-(4-ethoxy-phenylhydrazono)-1-phenyl-3-methyl-1H-pyrazolin-5(4H)-one (5a) (H-EMPhP) as ligand and its Cu(II), Co(II) and Ni(II) complexes 4(a-c) were synthesized and characterized by their thermal and spectral properties. The azocoupling product (H-EMPhP), able of azo-hydrazone tautomerism 5(a-d), act as a bidentate ligand involving in coordination the azogroup nitrogen of its common anion (7) and the oxygen atom that is bound to the pyrazole ring of the mentioned anion (7).

Formation of Pyridazinium Salts by Azo Coupling of N‐Substituted 3‐Amino‐1‐phenylbut‐2‐en‐1‐ones and Diazonium Salts

AbstractTreatment of 3‐(2,4‐dimethoxyphenylamino)‐ and 3‐methylamino‐1‐phenylbut‐2‐en‐1‐ones with some benzenediazonium tetrafluoroborates gives, besides the usual azo coupling products [i.e., 3‐(substituted imino)‐1‐phenylbutane‐1,2‐diones 2‐(4‐substituted phenylhydrazones) and 2‐(4‐methoxyphenyldiazenyl)‐3‐methylamino‐1‐phenylbut‐2‐en‐1‐one, respectively], the previously unreported 1,4,5,6‐tetrasubstituted pyridazinium tetrafluoroborates. The pyridazinium salts have been identified by X‐ray analysis and by their 1H, 13C, 15N, 11B and 19F NMR spectra. Their formation is most probably the result of nucleophilic attack on the carbonyl carbon by the nitrogen of the hydrazone group and subsequent dehydration. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Azo‐Coupling Reactions Used in Analytical Chemistry: The Role of Reactants, Intermediates, and Aqueous Medium

AbstractA quantum‐chemical study of the analytically important azo‐coupling reactions of naphthalen‐1‐amine (1) with naphthalene‐1‐diazonium (2) and 4‐sulphobenzenediazonium (8) cations has been carried out. The reactions have been found to be frontier‐controlled, and their regioselectivity is unequivocally determined by the thermodynamics of the intermediate σ‐complexes, as well as by the aqueous medium. The latter defines high positional selectivity, providing the decision between two possible reaction routes predicted on the basis of quantum‐chemical computations for separate molecular systems. As a result, azo coupling occurs at the 4‐ rather than at the 2‐position of 1. Furthermore, the aqueous medium makes the selection of analytical forms – protonated azo‐coupling products with a quinonehydrazone‐type structure.

Formation and reactions of substituted diazocyclopropanes and cyclopropyldiazonium ions

Decomposition of N-nitroso-N-cyclopropylureas at 5—7 °C on treatment with K2CO3 containing 15—20% H2O allows simultaneous generation of both substituted diazocyclopropanes and cyclopropyldiazonium ions, which can react according to 1,3-dipolar cycloaddition or azo-coupling pattern with appropriate substrates. The nature of substituents in the cyclopropyl ring have a pronounced influence on the product ratio (and, probably, on the equilibrium between the diazo compound and the diazonium ion). Thus, on treatment with a base in the presence of equimolar amounts of methyl metacrylate as a trap for the diazo compound and 2-naphthol as a trap for the diazonium ion, N-cyclopropyl- and N-(2,2-dimethylcyclopropyl)-N-nitrosourea azo coupling products predominate. Conversely, N-(2,2-dichlorocyclopropyl)-N-nitrosourea is transformed predominantly into 1,3-cycloaddition products. A rationalization for the experimental data is proposed.

An NMR and X-ray study of the structure of the azo coupling product of 4-dimethylaminopent-3-en-2-one and benzenediazonium-tetrafluoroborate.

4-Dimethylaminopent-3-en-2-one reacts with two molecules of benzenediazonium-tetrafluoroborate to give compound 1. The structure of this compound was determined by means of X-ray analysis of its crystal and 1H, 13C and 15N NMR spectra of its solution in CDCl3. The molecule of this compound contains one azo group and one hydrazone group. The substance exists, both in crystal form and in solutions of concentrations above 0.1 mol l(-1), in the form of a dimer, in which the pair of molecules are bound by two hydrogen bonds N-H...N. On diluting the solution, the dimers decompose, the two forms being in an equilibrium that is rapid on the NMR time scale.

Formation of Cyclopropylazoarenes in the Azo Coupling Reactions of the Cyclopropanediazonium Ion with Active Aromatic Compounds.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis, 1H, 13C and 15N NMR Study of Azo Coupling Products from Enaminones

Compounds 2 were prepared by the reaction of 3-amino-5,5-dimethylcyclohex-2-en-1-one and its N-phenyl derivative with substituted benzenediazonium tetrafluoroborates, and their 1H, 13C and 15N NMR spectra were measured and analysed. The active components react with enaminones in molar ratios of 2:1. Only in the case of 4-methoxybenzenediazonium tetrafluoroborate and 3-amino-5,5-dimethylcyclohex-2-en-1-one were traces of the product of the 1:1 reaction observed. The attack by the diazonium component occurs at carbon atoms C-2 and C-4, and the hydrazo form is always formed at the 2-position. 15N NMR spectroscopy was adopted to study the position of the tautomeric equilibrium (arylazo − arylhydrazono) at the 4-position: this equilibrium depends predominantly on the substituents of the amino group and, to a lesser extent, on the substituents of the diazonium component. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Tautomerism and hydrogen bonding in reaction products from 4-aminopent-3-en-2-one and diazonium ions

The azo-coupling products have been prepared from 4-aminopent-3-en-2-one and 4-chloro- or 4-nitrobenzenediazonium ion. Structure of the products obtained was studied by means of multinuclear NMR spectroscopy in CDCl 3 solutions and X-ray diffraction in solid state. Both products are predominantly present as azo forms in both the solution and the solid state, the azo form content being higher in solid state. The substituent effect on azo-hydrazone tautomeric equilibrium of the substances is more significant in solution than in solid state.

Formation of cyclopropylazoarenes in the azo coupling reactions of the cyclopropanediazonium ion with active aromatic compounds

The decomposition ofN-cyclopropyl-N-nitrosourea with K 2 CO 3 generates a cyclopropyldiazonium intermediate, which is trappedin situwith 1- and 2-naphthols, 2,7-dihydroxynaphthalene or 8-hydroxyquinoline to afford azo coupling products.

27Al, 15N, 13C and 1H NMR spectra and negative-ion electrospray mass spectra of the 2:1 aluminium(III) complexes of azo dyes derived from anthranilic acid

The 27Al, 15N, 13C and 1H NMR spectra in DMSO and mass spectra of 2:1 aluminium(III) complexes ( 1b– 4b) derived from anthranilic acid azo coupling products with 4-tert.butylphenol ( 1a), 2-naphthol ( 2a) acetoacetanilide ( 3a) 3-methyl-1-phenylpyrazol-5-one ( 4a) were measured and analysed. It was found that the aluminium atom was six-coordinated, being bound to two oxygens and the nitrogen originating from anthranilic acid.

The Reaction of 5-Aryl(hetaryl)-2-aroylmethylthio-1,3,4-oxadiazoles with Aryldiazonium Tetrafluoroborates

5-Aryl(hetaryl)-2-aroylmethylthio-1,3,4-oxadiazoles behave as CH acids and readily react with aryldiazonium tetrafluoroborates at the active methylene group to give azo coupling products. The spectroscopic properties of the compounds synthesized have been studied.

Amination of 1-Arylazo-4-chloroanthraquinones *

The simplest 1-arylazoanthraquinones have been known for a long time [1]. (4-Hydroxyphenylazo)anthraquinones typically give rise to azo3quinonehydrazone tautomerism [2], while the other chemical properties of these compounds were poorly studied. Taking into account high reactivity of various halogen-substituted anthraquinones in nucleophilic amination [3], we have examined the reactions of 4-chloro-1-(4-hydroxyphenylazo)anthraquinone (Ia) and 4-chloro-1-(4-dimethylaminophenylazo)anthraquinone (Ib) with cyclohexylamine, morpholine, and piperidine. Compounds Ia and Ib reacted with highly nucleophilic amines in dimethylformamide at 603 80oC and in dimethylacetamide at 50360oC within several hours (Scheme 1). The reactions with weakly nucleophilic amines required more severe conditions and were not selective. We failed to synthesize 4-amino-1-arylazoanthraquinones by the other method, namely by reaction of diazotized 1-amino-4-RNH-anthraquinones with phenol or dimethylaniline. In all cases, products of other transformations were isolated instead of the expected azo coupling products. For instance, from diazotized 1-amino-4-cyclohexylaminoanthraquinone and phenol in dimethylformamide we obtained 1,1-dimethyl-3-(9,10-dioxoanthracen-1-yl)triazene. When dimethylformamide was replaced by water, the product was 1-cyclohexylaminoanthraquinone. The latter was also obtained by attempted azo coupling of the same diazonium salt with N,N-dimethylaniline in dimethylformamide. The structure of compounds IIa3IIc and III was confirmed by elemental analyses and IR, H NMR, and mass spectra. 1-Cyclohexylamino-4-(4-hydroxyphenylazo)anthraquinone (IIa). A mixture of 1.1 mmol of anthraquinone Ia [4], 11 mmol of cyclohexylamine, and 5 ml of dimethylacetamide was stirred at 50360oC for 4 h (until initial anthraquinone Ia disappeared according to the TLC data). The mixture was cooled to room temperature and diluted with water. The dark brown tar-like precipitate was filtered off, washed with water and aqueous ethanol, dried, and subjected to column chromatography on silica gel (40/100 mm)

A New Entry for Short and Regioselective Synthesis of [1,2,4]Triazolo[4,3-b][1,2,4]-triazin-7(1H)-ones

Reaction of benzenediazonium chloride with active [1,2,4]triazin-3-ylthio-methylene compounds 3 afforded the azo coupling products 5, which yielded [1,2,4]triazolo[4,3-b][1,2,4]triazin-7(1H)-ones 8 upon treatment with sodium ethoxide in ethanol. The latter products 8 were characterized on the basis of alternate synthesis and spectral data. The mechanism of formation of 8 and the regiochemistry of the studied reactions are discussed.

15N,13C and1H NMR study of azo coupling products from diazonium salts and enaminones

Reactions of diazonium salts with 4-substituted phenylaminopent-3-en-2-ones produce the corresponding 4-phenylimino-3-phenylhydrazonopentan-2-ones. On the other hand, the reaction of diazonium salt with 4-amino(or 4-methylamino)pent-3-en-2-one gives a mixture of two isomers approaching the tautomeric form of 4-amino-3-phenylazopent-3-en-2-ones. The tautomeric form of the individual coupling products was determined by means of 13C and 15N NMR chemical shifts and J(15N,H) coupling constants. With the help of TPPI-NOESY spectra it was possible to follow the rate of mutual exchange of four protons of NH groups in both isomers of 4-amino-3-(4-methylphenylazo)pent-3-en-2-one. Copyright © 2000 John Wiley & Sons, Ltd.

27Al, 15N, 13C and 1H NMR spectra of the 2:1 aluminium(III) complexes of some azo dyes

The 27Al, 15N, 13C and 1H NMR spectra in DMSO and 27Al and 15N magic angle spinning NMR spectra of 2:1 aluminium(III) complexes derived from 5-chloro-2-hydroxyaniline azo coupling products with acetoacetanilide, 3-methyl-1-phenylpyrazol-5-one and 2-naphthol were measured and analysed. It was found that the aluminium atom is six-coordinated, being bound to two oxygens and the nitrogen originating from 2-hydroxy-5-chloroaniline of each ligand, in an analogous fashion to 2:1 cobalt(III) complexes described earlier. © 1998 John Wiley & Sons, Ltd.

27Al,15N,13C and1H NMR spectra of the 2:1 aluminium(III) complexes of some azo dyes

The 27Al, 15N, 13C and 1H NMR spectra in DMSO and 27Al and 15N magic angle spinning NMR spectra of 2:1 aluminium(III) complexes derived from 5-chloro-2-hydroxyaniline azo coupling products with acetoacetanilide, 3-methyl-1-phenylpyrazol-5-one and 2-naphthol were measured and analysed. It was found that the aluminium atom is six-coordinated, being bound to two oxygens and the nitrogen originating from 2-hydroxy-5-chloroaniline of each ligand, in an analogous fashion to 2:1 cobalt(III) complexes described earlier. © 1998 John Wiley & Sons, Ltd.

Novel in situ Formation and Rearrangement of Thiohydrazonate Esters

Reaction of benzenediazonium chloride with 3,4-diphenyl-1,2,4-triazol-5-ylthiomethylene compounds 3 afforded the azo coupling products 4, which upon treatment with sodium ethoxide in ethanol yielded the title compounds that rearrange in situ to give the thiohydrazides 7.

Synthesis of 4-diazo-3,5-dinitropyrazole and characteristic features of its behaviour towards nucleophiles

Diazopyrazole containing two nitro groups in the ring – 4-diazo-3,5-dinitropyrazole – has been synthesised for the first time by diazotisation of the corresponding aminodinitropyrazole. 4-Diazo-3,5-dinitropyrazole reacts with salts of methylene-active compounds, CH 2 (CN)NO 2 and CH 2 (COCH 3 ) 2 , to give azo coupling products, whereas its interaction with nucleophiles such as Br – , N 3 or H 2 O(H + ) involves replacement of one of the nitro groups yielding 4-diazo-3-R-5-nitropyrazoles.