Russian Chemical Bulletin最新文献

Pd-catalyzed amination of bromo derivatives of 2,3-diphenylquinoxaline with various di- and polyamines was studied. Polyamine substituents were introduced into positions 5 and 6 of quinoxaline cycle in the presence of the Pd(dba)₂—BINAP catalytic system in good yields (52–94%). In the case of long-chain polyamines, the reaction is complicated by the formation of N,N′-diarylated byproducts. Bis-amination of 6,7-dibromo-2,3-diphenylquinoxaline with 1,3-diaminopropane proceeds in significantly lower yield (45%) and requires the use of the Pd(dba)₂—DPPF catalytic system, whereas macrocyclic derivatives with polyamines with longer chains can be obtained using the Pd(dba)₂—JosiPhos and Pd(dba)₂—BINAP catalytic systems. Modification of the para-positions of the phenyl rings in 2,3-diphenylquinoxaline with ethylenediamine substituents can be performed in the presence of the Pd(dba)₂—BINAP system (42% yield), while modification of the meta-positions proceeds better in the presence of the JosiPhos ligand (56% yield). It was found that 2,3-bis(3-bromophenyl)quinoxaline, when reacted with 1,3-diaminopropane under these conditions, tends to form a macrocyclic derivative even in the presence of an excess of this diamine.

A new route was developed to prepare cis,trans,cis-ethyl 9-difluoromethyl-9-hydroxyhexahydropyrido[2,1-b]quinazoline-8-carboxylates or a mixture of trans- and cis-ethyl 7-R-9-methylhexahydropyrido[2,1-b]quinazoline-8-carboxylates (R = Me, Ph) by the three-component cyclization of α,β-enals and 2-(aminomethyl)aniline using ethyl 4,4-difluoroacetoacetate and ethyl acetoacetate, respectively, as a 3-oxo ester component under mild conditions. On heating, an alternative route to trans- and cis-(2,2-difluoro-1-hydroxyethyl)tetrahydropyrido[2,1-b]quinazolin-9-ones is the major one for ethyl 4,4-difluoroacetoacetate. The diastereomeric structures of the heterocycles were established by ¹H, ¹⁹F, and ¹³C NMR spectroscopy, including 2D ¹H—¹³C HSQC/HMBC and ¹H—¹H NOESY experiments, and X-ray diffraction.

A general method was developed for the nitrolysis of 3-R-1,5-dinitro-1,3,5-triazepanes, which is accompanied by the triazepane ring opening and N-nitration, to form linear nitramines as 1-acetoxy-2,5,7-trinitro-2,5,7-triazaoctane derivatives. The structures of these compounds were characterized by spectroscopic methods.

A new method for activation of the S₈ ring by the reaction with dimethyl phosphate-containing ionic liquids under mild conditions that meet the green chemistry principles was studied. The quantum chemical simulation of the reaction of cyclooctasulfur with 1,3-dimethylimidazolium dimethyl phosphate predicted the formation of the S—O polar covalent bond with simultaneous opening of the S₈ ring, which was confirmed experimentally. The reversibly formed 1,3-dimethylimidazolium (phosphonooxy)oligosulfanide is unstable in the presence of proton donors and to treatment with weak bases. The new thionation reaction of the 1,3-dimethylimidazolium cation to give 1,3-dimethylimidazoline-2-thione was found and the potential of (phosphonooxy)oligosulfanides for the formation of a liquid cathode for a lithium sulfur battery prototype was demonstrated for the first time.

New granulated adsorbent Al₂O₃ containing 0.25% graphene oxide (GO) was synthesized by spray drying, and the adsorption of diclofenac from aqueous solutions was studied. Diclofenac adsorption was carried out at room temperature at different pH values and adsorption times. The mechanism of diclofenac adsorption obeys the Langmuir model. The adsorbate molecules tend to cover homogeneous surface sites by a monolayer, and the adsorbate—adsorbate interactions are negligible in the range of low and medium surface coverages. The maximum adsorption capacity of the Langmuir monolayer was 29.67 mg g⁻¹. The obtained results show that the Al₂O₃—0.25 vol.% GO adsorbent is suitable for the production of adsorbents for additional purification of wastewater from diclofenac.

Experimental and theoretical data on the [2+2]-photocycloaddition (PCA) and reverse photoinduced cyclobutane ring opening (retro-PCA) reactions are considered. It is shown that for substituted ethylenes having an unsaturated substituent in conjugation with the ethylene π-bond, the mechanisms of forward and reverse reactions are fundamentally different. The forward PCA reaction proceeds in a concerted manner according to Woodward—Hoffman rules in the ππ*-excited state upon excitation of the whole conjugated π-system of the ethylene derivative including the ethylene group. The reverse opening of cyclobutane containing a substituent with a π-system proceeds stepwise by a predissociation mechanism if the substituent π-system rather than the cyclobutane σ-system is excited upon light irradiation. The reaction is initiated by energy transfer from the substituent to the cyclobutane ring, resulting in the formation of a tetramethylene biradical intermediate, which is further either fully cleaved or converted back to cyclobutane. All steps of the forward and reverse PCA reactions and the use of PCA as a mechanism of action of new-type photochromes are discussed in detail in relation to the biphotochromic covalently bonded dyads.

Approaches to the C—H functionalization are of great importance in modern organic synthesis. Among their diversity, reactions of the hydride transfer (HT) are especially effective. The major research efforts are focused on cascade of 1,5-HT/6-endo-cyclization reactions. Over the recent 20 or 30 years, alternative reaction pathways leading after the HT step to five-, seven-, eight-membered, and other cycles or non-cyclic products have been developed. The hydride transfer has become an independent tool for the multi-vector C—H functionalization. In this review, we attempted classifying approaches to the alternative reaction pathways triggered by the HT step, as well as to cover new achievements in this area.

A seven-cation layered double hydroxide with the composition MgNiCoAlFeYGd was obtained by soft mechanochemical synthesis followed by hydrothermal treatment. The crystal phase purity of the sample was confirmed by X-ray diffraction, and the unit cell parameters were calculated. Sorption and UV-photocatalytic properties were studied using the model dye methyl orange (MO). Oxidative properties were evaluated using the 3,3′,5,5′-tetramethylbenzidine (TMB) test. The valence state of cobalt was investigated by X-ray absorption near edge spectroscopy (XANES). The synthesized sample demonstrated oxidative activity toward TMB, as well as photocatalytic and sorption activity toward MO. According to the obtained results, cobalt contained in the sample is partially oxidized to the +3 oxidation state, which remains stable after the TMB test.

The review is devoted to electrosynthesis of electrically conducting polymers (ECPs) in the presence of macromolecular matrices (templates), in particular, sulfonated polyelectrolytes. Both general regularities of the process and its specific features characteristic of particular polymers are considered taking polyaniline, polypyrrole, and poly(3,4-ethylenedioxythiophene) as relevant examples. Particular attention is paid to the effect of the conformational state of the polyelectrolyte in an aqueous solution on the synthesis kinetics and on the structure and electrochemical, optical, and spectroelectrochemical properties of the resulting films of ECP—polyelectrolyte complexes. Understanding the role of the macromolecular matrix in electropolymerization and its influence on the structure and properties of the resulting ECP complexes can help in developing polymer films with predetermined functionality and improved life characteristics for applications in electrochromic, electroluminescent, and photovoltaic devices, in power sources, supercapacitors, chemical and biological sensors, etc.

The Tsuji—Trost reaction of diethyl malonate with (dimethyl)(vinyl)carbinol acetate in the K₂CO₃—DMF system in the presence of catalytic system Pd(dba)₂—1,3-diisopropyl-2-(2,2,2-trifluoro-1-phenylethoxy)-1,3,2-diazaphospholidine (a representative monocyclic diamidophosphite) affords the mixture of isomeric allylation products, 2-prenyl- and 2-[(dimethyl)(vinyl)carbinyl]malonates, in a 84: 16 ratio. In the case of unsubstituted allyl acetate, diethyl 2,2-diallylmalonate is quantitatively formed.