Vol 68, No 3 (2019)

The review is focused on premises, features and scope of the reactions leading to the direct functionalization of the C—H bond in arenes by the action of nucleophiles. Practical importance and a contribution of synthetic approaches with minimal steps, the so called PASE- (pot-, atom-, and step-economic) processes, to green chemistry are also discussed.

The mechanisms of formation and transformation of cyclohexyl hydroperoxide, cyclohexanol, and cyclohexanone in the liquid-phase oxidation of cyclohexane are reviewed. Cyclohexyl hydroperoxide is formed in chain propagation reactions and decomposes via the degenerate branching reactions under the action of alkoxyl, alkyl, and peroxyl radicals, as well as via nonradical channels to form alcohol and ketone. The radicals of two types, \({\rm{H}}{{\rm{O}}_2}^ \cdot \) radical and α-hydroxycyclohexylperoxyl radical, are involved in chain propagation in the course of cyclohexanol oxidation. In the chain propagation reactions, \({\rm{H}}{{\rm{O}}_2}^ \cdot \) radicals are more reactive than α-hydroxycyclohexylperoxyl radicals. The dynamic equilibrium was established in the dissociation of 1-hydroxycyclohexylperoxyl radical to cyclohexanone and radical \({\rm{H}}{{\rm{O}}_2}^ \cdot \). During oxidation of cyclohexane, cyclohexanone is formed from peroxyl radicals, as well as by the decomposition of cyclohexyl hydroperoxide and chain-radical oxidation of cyclohexanol. The oxidation of cyclohexanone in positions 2 and 6 affords 2-hydroperoxycyclohexanone, which predominantly decomposes to form 2-hydroxycyclohexanone. The oxidation of 2-hydroxy-cyclohexanone proceeds via the main channels of destruction of the carbon chain of cyclohexane leading to adipic acid and adipic anhydride. The oxidation products of C—H bonds of all types in alcohol and ketone are accumulated simultaneously with the oxidation products of C(1)—H bonds in cyclohexanol and of C(2)—H and C(6)—H bonds in cyclohexanone.

A homogeneous catalytic system containing palladium(ii) halides, diphenyl-m-sulfo-phenylphosphine (or palladium halide complexes with diphenyl-m-sulfophenylphosphine) and hydrohalic acid was developed and studied in the liquid-phase water gas shift reaction. The system based on palladium bromide and hydrobromic acid in aqueous acetic acid (20–40 vol.%) showed the highest activity. The dependences of the initial reaction rate on the concentrations of reagents and catalyst components were studied, a mechanism for the process was proposed, and a kinetic model was developed and found to agree well with experimental results.

Interactions in lanthanide—amino acid—β-cyclodextrin systems (amino acid = tryptophan, phenylalanine; lanthanide = Eu³+, Pr³+) were studied in aqueous solution. An analysis of the chemical shifts observed in the ¹H NMR spectra, as well as the ROESY data suggest the possibility for amino acid—lanthanide ion complexes encapsulated in the β-cyclodextrin cavity to form in solution. According to ROESY data, the indole ring of tryptophan and the phenyl group of phenylalanine enter the β-CD cavity from the wide rim side. Coordination with the metal ion occurs through the amino acid carboxyl group.

A comparative study of the sorption properties of N-(2-carboxyethyl)chitosan (CEC), N-(2-sulfoethyl)chitosan (SEC), N-(2,3-dihydroxy)propyl chitosan (HPC) and N-2-(2-pyridyl)ethyl chitosan (PEC) with respect to perrhenate ions in an acidic medium was carried out. On the basis of the analysis of the adsorption isotherms and the perrhenate ion adsorption degrees as functions of pH, it was found that the efficiency of adsorbents decreases in the sequence PEC > SEC > HPC > CEC. The investigated chitosan derivatives are characterized by a higher rate of sorption of perrhenate ions in comparison with known commercial anionites. In the case of PEC, accompanying ions have the least effect on the sorption.

Ferrocenium hexafluorophosphate reacts with aminophosphines P(NEt₂)₃, PhP(NEt₂)₂, Ph₂P(NEt₂), CyP(NEt₂)₂, and Prⁱ₂P(NEt₂) to form ferrocenylphosphonium salts [(C₅H₅)-Fe(C₅H₄PRR′R″)](PF₆), ferrocene, and [HPRR′R″](PF₆). The theoretical analysis of the reactions (M06-L/6-311++G(d,p)) showed that these reactions involve a sequence of the following steps: the addition of phosphine to the cyclopentadienyl ring, the oxidation of the initial adduct by the starting ferrocenium to give a dicationic η⁴-phosphocyclopentadiene complex with an agostic \(C_{sp^{3}}-H\rightarrow{Fe}\) bond, and the deprotonation of this bond to form ferrocenylphosphonium salts. The resulting ferrocenylphosphonium salts are resistant to alcoholysis and do not react with carbon disulfide.

1-Aminospiro[2.3]hexane-1,5-dicarboxylic and 1-ammo-5-(ammomethyl)spiro[2.3]hexane-1-carboxylic acids, which are the conformationally rigid analogues of glutamic acid and lysine, respectively, were synthesized from 3-methylidenecyclobutanecarbonitrile. The synthetic route includes a catalytic [1+2]-cycloaddition of ethyl 2-diazo-2-nitroacetate to a double bond of the unsaturated nitrile, a subsequent chemoselective reduction of the nitro and cyano groups, and a hydrolysis of the ester moiety.

Copolymers of perfluoro-2-ethyl-2-methyl-1,3-dioxole and perfluoro-5-methyl-3,6-dioxanon-1-ene were synthesized using high-pressure technique without initiators. Copolymers have molecular weight of (1.2–4) • 10⁴ and possess high optical transparency in the telecommunication C-band region of 1530–1565 nm. Refractive index n of copolymers as a function of ether mol.% in the macromolecule x was investigated. It is established that the curve n(x) is non-monotonic, the difference of refractive indices of copolymers with various x differs by Δn = 0.015. The synthesized materials are amorphous, capable of film formation, and can be used for the fabrication of optical fibers and integrated optical waveguides with numerical aperture NA from 0.13 to 0.2, with waveguiding core and cladding made of perfluorinated materials.

New unsaturated derivatives of the furan series, diallyl esters of furan-2,5-dicarboxylic acid and 5,5′-[oxybis(methylene)]di(2-furoic acid), which can be used as monomers and cross linking agents, were synthesized by the aerobic oxidation of 5-hydroxymethylfurfural and 5,5′-oxybis(5-methylene-2-furaldehyde) obtained by catalytic dehydration of fructose. Optimum conditions for the synthesis of the above-mentioned compounds and their copolymerization with butyl methacrylate were determined. Varying the amount of the cross-linking agent, the thermal stability, adhesion, strength and optical properties of copolymers can be controlled. New cross-linking agents obtained from renewable resources can be considered as an alternative to the important cross-linking agent, diallyl phthalate, produced from petroleum.

Bichromophoric dyads containing two styrylbenzo[f]quinoline fragments linked by 1,2-phenylene or 2,3-naphthylene moiety connected to the styryl groups of these fragments via oxy and carboxy functional groups with alkyl bridges of different length were synthesized.

N,N-Di(pyridin-2-yl)quinolin-6-amine which is a new ditopic fluorescent ligand based on di(pyridin-2-yl)amine was synthesized and characterized. Using the methods of fluorescence and UV-vis spectroscopy, the complex formation of this ligand with the Co^II, Ni^II, Qu^II, Zn^II and Pb^II cations in acetonitrile was studied, the composition and the stability constants of the resulting complexes were determined. Their structure was studied by NMR using the zinc complex as an example.

A three-component one-pot procedure to synthesize 2,4-disubstituted b-fused 3,4-dihydro-2H-thiopyran derivatives by the Diels—Alder reaction of the in situ generated α,β-enethiones with maleic acid derivatives was developed. The reactivity of different unsaturated thioketones as dienes and maleic acid derivatives as dienophiles under the developed reaction conditions was studied.

Unstable under normal conditions sodium and lithium 3-tert-butyl-8-lithio-7-R-4-oxopyrazolo[5,1-c][1,2,4]triazin-1-ides were generated for the first time by the reaction of 8-bromo-7-R-3-tert-butyl-4-oxopyrazolo[5,1-c][1,2,4]triazines (R = H, NHCOCF₃) with BuⁿLi in THF in the −97H÷−84 °C temperature range. The triazinides were trapped in the reactions with various electrophiles (H₂O, CH₃I, ArCHO, DMF, R¹COCl) to selectively synthesize new C(8)-functionalized 4-oxopyrazolo[5,1-c][1,2,4]triazines.

The reactions of 4-aryl-N-hetaryl-2-hydroxy-4-oxobut-2-enamides (hetaryl is 2-pyridyl, 2-azolyls, benzo[d]thiazol-2-yl) with hydroxylamine yielded 4-aryl-N-hetaryl-2-hydroxyimino-4-oxobutanamides and 5-aryl-N-hetarylisoxazole-3-carboxamides. The products were searched for representatives with high antimicrobial and anti-inflammatory activities and low acute toxicity. A structure—pharmacological activity relationship of the prepared compounds was established.

An approach for the synthesis of new organic ligands combining in their structure pyridine, benzothiazole, and polyethylene glycol fragments was developed, proceeding from 6-hydroxy-2-(pyridin-2-yl)benzothiazole and mono- or ditosyl-substituted polyethylene glycols. The ligand 2-(2-{[2-(pyridin-2-yl)benzothiazol-6-yl]oxy}ethoxy)ethanol (L) in the reaction with Cu(ClO₄)₂•6 H₂O and CuCl₂•2 H₂O formed coordination compounds of the composition L₂Cu(ClO₄)₂•7 H₂O and LCuCl₂•0.5 H₂O, respectively.