Showing papers on "Triazene published in 1981"

A condition variation study for radioiodination via triazene intermediates

Abstract: Pyrrolidyl triazenes prepared by interception of the diazonium transient in the Sandmeyer reaction of amines can serve as useful intermediates in the iodination and radioiodination of aryl rings. Decomposition of such triazenes in the presence of iodide is acid-catalyzed and is sensitive to choice of solvent, acid, and triazene structure. A condition variation study by HPLC of four different solvent systems and two non-nucleophilic acids was carried out on the123I iodination of the triazenes of p-nitroaniline, p-anisidine and p-toluidine. This method has proven useful in radiolabeling of two pharmaceutical analogs which were not amenable to labeling through the classic Sandmeyer method.

Active-site-directed irreversible inhibition of glycosidases by the corresponding glycosylmethyl-(p-nitrophenyl)triazenes

Abstract: β-D-Galactopyranosylmethyl-(p-nitrophenyl)triazene is an active-site-directed irreversible inhibitor (ASDIN) of the ebg° and the lacZβ-galactosidases of Escherichia coli, of the β-galactosidase of human-liver lysosomes, and, less effectively, of the α-galactosidase of green coffee beans; it has no effect on the lac repressor of E. coli. β-D-Glucopyranosylmethyl-(p-nitrophenyl)triazene is an ASDIN of both β-glucosidase and β-galactosidase activities of sweet-almond β-glucosidase B; it has no effect on yeast α-glucosidase, the lacZβ-galactosidase of Escherichia coli, or glucoamylase from Aspergillus niger. β-D-Xylopyranosylmethyl-(p-nitrophenyl)triazene is an ASDIN of the β-xylosidase from Penicillium wortmanni, but has no effect on the β-xylosidase of Bacillus pumilus, except by virtue of its consumption of stabilising dithiothreitol. α-L-Arabinofuranosylmethyl-(p-nitrophenyl)triazene is an ASDIN for the extracellular α-L-arabinofuranosidase of Monilinia fructigena of more alkaline pH optimum at pH 7; the other isoenzyme is inert at this pH, and more acidic pHs destroy the reagent. It is concluded that glycosylmethyl(aryl)triazenes are ASDINs for glycosidases for which both substrate and product stereochemistries at the anomeric centre are the same as that of the reagent; that they can act, with lower effectiveness, on glycosidases for which both substrate and product stereochemistries are opposite to that of the reagent; and that they have no effect on glycosidases with opposite stereochemistries of substrate and product, or proteins of no catalytic function.

Electronic Absorption and Emission Spectra of 1, 3-Diaryltriazenes†

Abstract: The Pariser-Parr-Pople (PPP) type LCI-SCF-MO calculations were used to study the models of 1, 3-diphenyltriazene (1), 1, 3-bis(3-pyridyl)triazene (2), 1, 3-bis (2, 4-dichlorophenyl)triazene (3), and 1, 3-bis (4-ethoxycarbonyl)triazene (4). The results of the calculations were compared with the experimental electronic absorption and emission (fluorescence, phosphorescence) spectra of these compounds.

Possibility of the Intramolecularity of Triazene Rearrangement

Abstract: The mechanism for the ortho-rearrangement of diaryltriazenes still remains equivocal. An interesting result suggesting an intramolecular nature of the triazene rearrangement was obtained on the basis of the effect of concentration of added N,N-dimethylaniline in the ortho-rearrangement of 1,3-bis(4-methylphenyl)triazene (1). The ortho/para ratio for the rearrangement of 1,3-diphenyltriazene (4) tends to increase with an increase of the viscosity. The results are discussed on the basis of increasing nucleophilicity of free amine by H-bonding with dimethylaniline and favoring ortho-migration with viscosity, respectively.

Triazene metabolism. I. The effect of substituents in the aryl group on the kinetics of enzyme-catalysed N-demethylation of 1-aryl-3,3-dimethyltriazenes

Abstract: A series of antitumor dimethylaryltriazenes (ArN==N . NMe2) have been studied with respect to enzyme catalysed N-demethylation by liver microsomes and the Km values determined by Lineweaver-Burk treatment. The substituent in the aryl group of the triazene does not significantly effect the magnitude of Km, which is of the same order of magnitude as the Km for aminopyrine. On the other hand, dimethyltriazenes appear to have lower Km values for demethylation than the structurally similar dimethylnitrosamines. Monomethyltriazenes, the proposed active metabolites of the dimethyltriazenes, do not undergo appreciable demethylation in the presence of microsomes and it appears that the dimethyltriazenes only demethylate once during metabolism. Spontaneous formaldehyde release from the hydroxymethyltriazene in the presence of the Nash reagent prevented an analogous study of the metabolism of these compounds.

Triazene metabolism. II. Transportability and enzyme inhibitory characteristics of metabolites of antitumor dimethyltriazenes.

Abstract: A series of dimethyltriazenes (Ar∙N=N∙NMe2), monomethyltriazenes (Ar∙N=N∙NH∙Me), and triazene carbinolamines (Ar∙N=N∙NMe∙CH2OH) have been studied for their inhibitory effects on the enzyme, hog liver esterase (EC 3.1.1.1). p-Nitrophenyl acetate was used as the model substrate and the rate of hydrolysis was followed spectrophotometrically at 400 nm, the absorption maximum of the p-nitrophenylate ion. Only triazenes with an ester group in the aryl moiety exhibited significant inhibition. Preincubation of the enzyme with the monomethyltriazene (MeO2C∙C6H4∙N=N∙NHMe) or the methyloltriazene (MeO2C∙C6H4∙N=N∙NMe∙CH2OH) gave enhanced inhibition, which was not observed when the dimethyltriazene (MeO2C∙C6H4∙N=N∙NMe2) was preincubated with the enzyme. Inhibition of enzyme activity by the monomethyltriazene was shown to be essentially irreversible, whereas the model substrates, methyl benzoate and methyl p-aminobenzoate, gave reversible inhibition in the same assay. The inhibition by the N-methyloltriazene was only p...

Production of p-phenylenediamine

Abstract: A 1,3-diphenyltriazene rearrangement product obtained by contacting an aniline solution of the triazene with 0.4-2% of a strong acid, preferably HN0 3 , which product, at 25-40°C, is a two-phase liquid having (1) an organic phase in which p-aminoazobenzene and water are dissolved in aniline, and (2) an aqueous phase, is separated into organic and aqueous phases, and the organic phase thereafter contacted with an aqueous extracting base, e.g., NH 4 0H, which reduces the strong acid concentration of the organic phase. The organic phase then is separated and is ready for conversion to p-phenylenediamine by catalytic hydrogenation. Higher catalyst activity and productivity result when the rearrangement product is treated as described prior to the hydrogenation.

Alkylation of silver salt of 1-phenyl-3-acetyltriazene by alkyl halides

Abstract: 1. We were the first to show that a linear triazene can be alkylated at the central nitrogen atom. 2. The Ag salt of 1-phenyl-3-acetyltriazene reacts with alkyl halides in an aprotic medium to give either 1-phenyl-3-acetyl-2-alkylazimines or 1-phenyl-3-alkyl-3-acetyltriazenes.

An experimental and theoretical study of dipole moments of n-alkyl-1,3-bis-(p-chlorophenyl)triazenes and 1-(3,4-dimethyl-5-isoxazolyl)-3-aryltriazenes

Abstract: The dielectric constants, densities, and the refractive indices of dilute benzene solutions have been used to obtain the experimental dipole moments of 1,3-diphenyltriazene (1a), 1,3-diphenyl-3-methyltriazene (Ib), 1,3-bis( p -chlorophenyl)triazene (IIa), its N -alkyi derivatives (IIb-IIg), and 1-(3,4-dimethyl-5-isoxazolyl)-3-phenyltriazene (IIIb) and its N -methyl derivative (IIIc). The results show that the dipole moment of IIa is increased by an increment of about 0.77 D (average value for methyl, ethyl, n-propyl, allyl, and benzyl) on N -alkyl substitution. The increment for the n-butyl group is Δμ = 1.19 D. Some of the experimental values are compared with those from PPP and CNDO/2 calculations.