I. A. Os’kina

Kinetics of the reaction of 4-nitrophenyl benzoates with 4-chlorophenol in the presence of potassium carbonate in dimethylformamide

The effect of the substituent in the benzoyl group on the relative rate and activation parameters of transesterification of substituted 4-nitrophenyl benzoates with 4-chlorophenol in dimethylformamide in the presence of potassium carbonate was studied by the competing reaction technique. The whole series of benzoates showed the enthalpy-entropy compensation effect. 4-Nitrophenyl benzoates having electronacceptor substituents give rise to isokinetic relationship with an isokinetic temperature β of 382 K. The mechanism of the transesterification process is discussed.

Activation parameters of the reactions of 4-nitrophenyl benzoates and S-phenyl benzothioate with 4-chlorophenol in dimethylformamide in the presence of potassium carbonate

The kinetics of transesterification of 4-nitrophenyl benzoates and S-phenyl benzothioate with 4-chlorophenol in dimethylformamide in the presence of potassium carbonate were studied. Variation of the substrate reactivity and activation parameters of the process is discussed with respect to the substituent in the benzoic acid fragment.

Kinetics of the reaction of substituted 4-nitrophenyl benzoates with benzenethiol in the presence of potassium carbonate in dimethylformamide

The effect of the substituent nature on the rate and activation parameters of transesterification of a series of 4-nitrophenyl benzoates with benzenethiol in dimethylformamide in the presence of potassium carbonate was studied by the competing reaction method. In all cases, change of the Gibbs energy of activation is determined mainly by variation of the enthalpy of activation. 4-Nitrophenyl benzoates having electron-withdrawing substituents in the benzoyl fragment were found to fit an isokinetic relation with an isokinetic temperature β of 318 K. Enthalpy-entropy compensation effect was observed in the reactions with all the examined 4-nitrophenyl benzoates. The relation between the reactivity and polarizability of nucleophilic center in S-and O-nucleophiles is discussed.

Photocyclization of 2-azido-1-(4-tert-butylphenoxy)-9,10-anthraquinone in the presence of substituted phenols

New types of phototransformations in the quinone series, viz., photocyclizations of 1-aryloxy-2-azido-9,10-anthraquinone in the presence of phenols, were studied. The photolysis affords mainly 5H-naphtho[2,3-c]phenoxazine-8,13-diones, in which the nitrogen atom is covalently bound to the phenyl ring of the attached phenol. As a result, complex polycyclic derivatives of phenoxazines were prepared in high yields in one step.

Effect of nucleophile on the activation parameters of transesterification of 4-nitrophenyl benzoates

Activation parameters of the reaction of 4-nitrophenyl benzoates with benzenethiol in the presence of potassium carbonate in dimethylformamide were determined. The entropies of activation for the reactions of unsubstituted 4-nitrophenyl benzoate and 4-nitrophenyl benzoates having donor substituents are positive. The relative contributions of the enthalpy and entropy of activation to the Gibbs energy of activation are discussed. Variation of the activation parameters upon replacement of benzenethiol by 4-chlorophenol is analyzed.

Kinetics of the reaction of 1-R-3,5-dinitrobenzenes with 4-chlorophenol in DMF in the presence of potassium carbonate

The effect of substituent in 1-R-3,5-dinitrobenzenes on the rate and activation parameters of their reactions with 4-chlorophenol in dimethylformamide in the presence of potassium carbonate was studied by the competing reactions technique. Analysis of the activation parameters revealed predominant contribution of the enthalpy factor to variation of the Gibbs energy of activation.

Activation parameters of transesterification of 4-nitrophenyl acetate in the presence of K2CO3 in DMF

The activation parameters for the reactions of 4-nitrophenyl acetate with 4-chlorophenol and benzenethiol in the presence of potassium carbonate in dimethylformamide were determined. Depending on the substrate structure, the enthalpy and entropy of activation decrease in going from 4-nitrophenyl acetate to 4-nitrophenyl benzoate, while the Gibbs energy of activation increases.

Synthesis of substituted 2-(thiophen-2-yl)-1H-imidazol-1-ols

Substituted 2-(thiophen-2-yl)-1H-imidazol-1-ols were synthesized by cyclization of the corresponding α-thienyl nitrones in alkaline medium. α-Thienyl nitrones were obtained by reaction of N-(1-hydroxyimine-1-R-propan-2-yl)hydroxylamines with thiophene-2-carbaldehyde in methanol. At boiling α-thienyl nitrones in methanol in the presence of sodium methylate 5-aryl(hetaryl)-2-(thiophen-2-yl)-1H-imidazol-1-ols are formed chemoselectively.

Synthesis of nucleosides containing a photolabile 2-(2-nitrophenyl)propoxycarbonyl group

At present, DNA biochips are widely used in medicine as diagnostic systems [1, 2]. Oligonucleotide biochips are often obtained with the aid of photolabile protecting groups [3–7]. The latter should be stable under the conditions of oligonucleotide synthesis but should be readily removed by photolysis without involving the protected moiety. A widely used photolabile protecting group is the o-nitrobenzyl group [3, 8–10]. The goal of the present work was to extend the series of nucleosides protected by the photolabile 2-(2-nitrophenyl)propoxycarbonyl group and containing readily removable protecting groups in the aromatic heteroring, which can subsequently be used in the design of oligonucleotide biochips. We have synthesized previously unknown nucleosides 4–7. Compounds 4 and 5 were obtained by acylation of 2′-deoxyguanosine and 2′-deoxyadenosine with phenoxyacetyl chlorides 1 and 2, respectively. Nucleosides 6 and 7 protected by photolabile 2-(2-nitrophenyl)propoxycarbonyl groups were synthesized by treatment of compounds 4 and 5, respectively, with 2-(2-nitrophenyl)propyl chloroformate (3) which was prepared as described in [10]. Compounds 6 and 7 were isolated as mixtures of diastereoisomers. ISSN 1070-4280, Russian Journal of Organic Chemistry, 2015, Vol. 51, No. 1, pp. 141–144.

Synthesis of 3-Hydroxy-2-hydroxy(phenyl)methyl-3-methyl-2,3-dihydro-4H-furo[3,2-c]chromen-4-one from 4-Hydroxycoumarin

4-Hydroxycoumarin derivatives include a number of compounds exhibiting biological activity. An important place in this series is occupied by furocoumarins possessing diverse pharmacological properties: antifungal, zoocidal, anticoagulant, spasmolytic, etc. [1–6]. Furocoumarins can be isolated from natural sources [7] or synthesized [8–11]. Methods of synthesis of furocoumarins are based on C-alkylation of 4-hydroxycoumarin with α-halo ketones or halo alkynes with subsequent cyclization [9, 10] or on oxidative addition of olefins to 4-hydroxycoumarin in the presence of silver(I) salts [11].