Dimerization of sterically hindered p-nitrosophenols

Semin, I. V.; Sokolenko, V. A.; Tovbis, M. S.

doi:10.1134/s1070428007040094

Cited by 6 publications

(4 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Dialkyl 2-hydroxy-4,6-dimethyl-5-nitrosobenzene-1,3-dicarboxylates Ia-Id were synthesized in a way similar to cyclization of isonitrosoacetylacetone with dialkyl acetonedicarboxylates [2]. Isonitrosoacetylacetone, 5 mmol, and the corresponding dialkyl acetonedicarboxylate, 10 mmol, were added to a solution of 5 mmol of potassium hydroxide in 5 ml of anhydrous alcohol.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Catalytic hydrogenation of persubstituted p-nitrosophenols

et al. 2010

Self Cite

View full text Add to dashboard Cite

Catalytic hydrogenation of dialkyl 2-hydroxy-4,6-dimethyl-5-nitrosobenzene-1,3-dicarboxylates over Pd/C gave the corresponding previously unknown dialkyl 5-amino-2-hydroxy-4,6-dimethylbenzene-1,3-dicarboxylates. The first-order rate constants for the hydrogenation process were found to be linearly related to steric constants of the alkyl groups. Scheme 1. R = Me (a), Et (b), Pr (c), Bu (d).We previously reported on exhaustively substituted nitrosophenols having ethoxycarbonyl groups in the ortho positions with respect to the hydroxy group [1,2]. We synthesized analogous nitrosophenols with methoxy-, propoxy-, and butoxycarbonyl groups and performed their hydrogenation with a view to obtain new p-aminophenols. The expected products contain both salicylic acid ester and p-aminophenol fragments that are typical of known medicines [3]; therefore, they attracted interest from the viewpoint of synthesis of biologically active compounds.Dialkyl 2-hydroxy-4,6-dimethyl-5-nitrosobenzene-1,3-dicarboxylates Ia-Id were subjected to hydrogenation over carbon-supported palladium in anhydrous ethyl acetate. The reactions were carried out in a reduction cell maintained at a constant temperature.The cell was charged with the solvent, initial nitrosophenol, and catalyst, and hydrogen (from a steel cylinder) was bubbled through the mixture. The target products were isolated as follows: the reaction mixture was filtered from the catalyst and was saturated with dry hydrogen chloride. Dialkyl 5-amino-2-hydroxy-4,6-dimethylbenzene-1,3-dicarboxylate hydrochlorides separated from the solution and were filtered off.We also performed kinetic measurements. Kinetic curves were plotted for the consumption of hydrogen, and dependences of ln(V o -V x ) versus time were obtained. The regression equation for the hydrogenation of compound Ia was as follows: y = -0.05 x + 3.38, r = 0.994. The dependences for other substituted nitrosophenols Ib-Id of this series were also linear and were characterized by high correlation coefficients, indicating that catalytic hydrogenation of compounds Ia-Id under the given conditions conforms to first-order kinetics. From the obtained dependences we calculated the first-order rate constants (k, s -1 ) for hydrogenation of all the examined dialkyl 2-hydroxy-4,6-dimethyl-5-nitrosobenzene-1,3-dicarboxylates Ia-Id: Ia, 5.01; Ib, 3.03; Ic, 0.92; Id, 0.83. It is seen that the hydrogenation rate constant strongly depends on the length of the alkyl radical in the ester moiety: it decreases in going from methyl to butyl esters.We revealed a linear relation between the logarithms of hydrogenation rate constants and steric constants of alkyl groups E s . The following steric constants E s were used: 0.00 (Me), -0.09 (Et), -0.30 (Pr), and -0.34 (Bu) [4]. The regression equation was y = 2.35 x + 1.30, r = 0.998. We can conclude that the difference in the rates of catalytic hydrogenation is determined exclusively by the size of the alkyl group in the ester fragments.

show abstract

Section: Methodsmentioning

confidence: 99%

“…We previously reported on exhaustively substituted nitrosophenols having ethoxycarbonyl groups in the ortho positions with respect to the hydroxy group [1,2]. We synthesized analogous nitrosophenols with methoxy-, propoxy-, and butoxycarbonyl groups and performed their hydrogenation with a view to obtain new p-aminophenols.…”

mentioning

confidence: 99%

Catalytic hydrogenation of persubstituted p-nitrosophenols

et al. 2010

Self Cite

View full text Add to dashboard Cite

show abstract

“…were obtained similarly to the cyclization of isonitrosoacetyl-acetone with dialkyl acetonedicarboxylate [2]. In 2 mL of anhydrous alcohol was dissolved 0.25 mmol of potassium hydroxide, and 0.25 mmol of 2-hydroxyimino-1-[pyridin-3(4)-yl]-butane-1,3-dione and 0.5 mmol of dialkyl acetonedicarboxylate was added.…”

Section: Potassium 26-di(alkoxycarbonyl)-3-methyl-4nitroso-5-[pyridimentioning

confidence: 99%

Synthesis of potassium 2,6-di(alkoxycarbonyl)-3-methyl-4-nitroso-5-[pyridin-3(4)-yl]phenolates

et al. 2015

Self Cite

View full text Add to dashboard Cite

SHORT COMMUNICATIONSHexasubstituted nitrosophenols with methoxy-, ethoxy-, propoxy-, butoxycarbonyl substituents in the positions 2, 6 were obtained by the reaction of acetonedicarboxylic acid esters with isonitrosoacetylacetone [1-3]. Nitrosophenols are readily reduced into aminophenols [4] that at the modification of the amino group are transformed into compounds exhibiting the antiarrhythmic action [5]. The introduction of a pyridine residue into the molecule may enhance the biologic action and extend the range of useful applications since the substituted pyridines are already for a long time used as drugs [6].

show abstract

“…For these compounds dissolved in aqueous alkali gradual change of the colour from orange to brilliant-green has been observed. Based on the changes in the UV spectra it has been assumed [9], that there is a slow dimer (II) decomposition into two molecules of the monomer (I) salt according to Scheme 1:…”

Section: Introductionmentioning

confidence: 99%