The catalytic effect of alkali metal carbonates, in situ generated carbene, and anionite in the transesterification reaction of alkyl benzoates with methanol, ethanol, benzyl alcohol, and cyclohexanol, as well as vegetable oils with methanol and ethanol was studied. Catalytic reactions with methanol occur at room temperature with yields close to quantitative. The reactions of the vegetable oils in the presence of potassium carbonate with small amounts of methanol or ethanol (3.2 eq) at room temperature lead to high yields of biodiesel fuel and are suitable for industrial use.

New catalytic methods of hydrodehalogenation reaction of haloarenes for the disposal of toxic production waste and persistent organic pollutants, fine organic synthesis, and solution of green chemistry issues are discussed. Methods presented in the review are based on electron transfer reactions involving photo- and electrocatalytic processes, including those with the participation of metal nanoparticles. Reactions of deuterodehalogenation of haloarenes and several aspects of biological methods of the process are analyzed.

New electronic philicity indices Ie, P for donor-acceptor interactions of a wide range of carbenes of both nucleophilic and electrophilic type were assessed using the DFT methods. For typical nucleophilic neutral carbenes and hydrogen ions PH are in the range of 1.4-2.8 eV, PH ' 1.5- 1.9, IeH 9.5-11.9 eV; for typical electrophilic carbenes pH 0-0.6 eV, PH ' 1.0- -0.3, IeH - 2.0-3.6 eV. The electronegativities chi and global electrophilicities omega of the same carbenes for one-electron processes were also determined. It was established that the electronegativity is suitable criterium of philicity. For typical nucleophilic neutral carbenes omega are in the range of 0.1-1.1 eV, chi 1.5-3.9 eV, for typical electrophilic carbenes omega 1.4-4.9 eV, chi 4.7-7.1 eV. The data obtained can be used in the design of structures for synthetic and practical applications.

New carbene complex catalysts based on palladium chloride, including PEPPSI-complexes (PEPPSI = Pyridine-Enhanced Precatalyst Preparation Stabilization and Initiation), have been synthesized. These catalysts show high efficiency in Buchwald–Hartwig C–N cross-coupling between aryl chlorides/bromides and amines, including sterically shielded reagents, and high efficiency in the Suzuki–Miyaura C–C cross-coupling reaction, where their use results in the formation of several tetra-ortho-substituted biaryls at very low amounts of catalyst under mild conditions. Modification of the catalyst structure to the PEPPSI complex leads to an unexpected decrease in activity in the Buchwald–Hartwig amination, in contrast to the Suzuki–Miyaura reaction, in which the PEPPSI complex showed greater activity in some cases.

New carbene complexes of copper (I), silver and palladium, including ionic carbene-phenanthroline complexes, were synthesized on the basis of imidazole, benzimidazole, 1,2,4-triazole systems with cetyl and aryl including fluorophenyl substituents. The study of the antimicrobial action of the synthesized compounds revealed high antibacterial and antifungal activities of fluoro- and phenanthroline-containing carbene complexes.

New catalytic methods for the hydrodehalogenation of haloarenes with hydrogen and hydrogen-containing reagents (metal and non-metal hydrids, organic hydrogen-containing compounds, etc.), which are essential for fine organic synthesis and neutralization of toxic production waste and persistent organic pollutants. The paper focuses on such catalysts as complexes of stable heterocyclic carbenes, transition metals, and nanosized metal particles and their composites, as the most promising for industrial chemistry. Catalysts with particularly high efficiency have been highlighted.

The synthesis of a number of carbene PEPPSI-complexes of palladium with various pyridine and carbene ligands was carried out by reactions of 1,3-bis-(2,6-dibenzhydryl-4-methyl­phenyl)imidazolium chloride IPr*.HCl [compounds 7a-c IPr*PdCl2L’, L’ = pyridine (а), 3-chloropyridine (b), 4-dimethylaminopyridine (с)], 1,3-bis-(2,6-diisopropylphenyl)­imida­zo­li­um perchlorate IPr.HClO4 [compounds 8a,b IPr.PdCl2L’, L’ = 3-chloropyridine (а), о-phenanthroline (b)], 1,3-diphenyl-4-(2,6-diisopropylphenyl)-1,2,4-triazolium perchlorate L.HClO4 (complex 9 LPdCl2L’, L’ = 3-chloropyridine) and 1,3-dicetyl­imidazolium bromide L.HBr (complex 11 LPdCl2L’, L’ = pyridine) with palladium chloride in pyridines (pyridine, 3-chloropyridine), or acetonitrile in the presence of potassium carbonate. Yields of compounds – from high (56–100%) to moderate (36 %). The structure of the compounds was confirmed by 1H and 13C NMR spectroscopy. Chemical shifts of carbene atoms in the 13C NMR spectra of complexes 7a-c. 8a, b 11 are in the region 151.0-156.2 ppm, for complex 9 - at  174.4 ppm A high catalytic effect of sterically shielded complexes 7a, b, 8a, b in the hydrodehalogenation reaction of p-dichlorobenzene and hexachlorobenzene under the action of potassium tert-butoxide in isopropanol was established. 1,3-Bis-(2,6-dibenzhydryl-4-methylphenyl)-imidazol-2-ylidene complexes 7a, b (quantitative conversions with p-dichlorobenzene are achieved with 0.013 mol% of catalyst) show the highest efficiency, but the compound with 4-dimethylaminopyridine ligand 7c has significantly lower efficiency (22% conversion under these conditions). Complexes with 1,3-bis-(2,6-diisopropylphenyl)-imidazol-2-ylidene ligand 8a, b are close in efficiency to compounds 7a, b (for 7a quantitative conversion is achieved with 0.026 mol% of catalyst). Phenanthroline-containing complex 8b is less effective than complex 8a (87% conversion with 0.052 mol% of catalyst). Complex 9 is much less effective (even with 0.13 mol% of catalyst 13% conversion is achieved). Compound 11 catalyzes the reaction well only when the amount of catalyst is up to 1.3 mol% (98% conversion). Thus, compounds 7a, b, 8a are the best PEPPSI-catalysts for hydrodehalogenation of haloarenes promising for industrial decontamination of persistent orga­nic pollutants (hexachlorobenzene, DDT, di­oxins and polychlorinated biphenyls, etc.).

Aim. To synthesize aliphatic and aromatic derivatives of salt carbenoid compounds of the series of imidazole, benzimidazole, pyridine, pyrimidine and 1,3,4-oxadiazole containing fluorophenyl, cetyl or adamantyl substituents, and study their antimicrobial (antibacterial and antifungal) activities.Results and discussion. New derivatives of heterocyclic carbenoid salts and zwitterions based on the imidazole, benzimidazole, pyridine, pyrimidine and 1,3,4-oxadiazole heterocyclic systems containing fluorophenyl, cetyl or adamantyl substituents were synthesized. For this purpose, reactions of cyclization of the corresponding diimines with ethoxymethyl chloride (imidazolium salts), quaternization of the corresponding azoles with cetyl bromide or 1-adamantyl bromide in organic solvents (benzimidazolium, pyridinium and 1,3,4-oxadiazolium salts), cyclization of di(1-adamantylamino)alkanes hydrobromides with the orthoformic ester (4,5-dihydroimidazolium and tetrahydropyridinium salts) were used. Zwitterionic compounds were obtained by the reaction of the corresponding azolium salts with phenyl isothiocyanate in the presence of potassium carbonate. Some macrocyclic and adamantyl substituted heterocyclic compounds showed antifungal and antibacterial activities.Experimental part. The structure of the compounds synthesized was proven by 1H and 13C NMR spectroscopy methods. The antimicrobial activity was studied out by the agar diffusion method to determine diameters of the growth inhibition zones of microorganisms (bacteria and fungi) and by the method of serial dilutions to determine the minimum inhibitory concentration and minimum bactericidal and fungicidal concentrations.Conclusions. The synthesis of new heterocyclic carbenoid salts and zwitterions based on the imidazole, benzimidazole, pyridine, pyrimidine and 1,3,4-oxadiazole heterocyclic systems containing fluorophenyl, cetyl or adamantyl substituents has been performed. Compounds of macrocyclic and adamantyl heterocyclic series with antifungal and antibacterial activities have been found. 1,3-Dicetylimidazolium bromide, macrocyclic bis(decylenebenzimidazolium) bromides, azolium-N-phenylthiocarboximides have been proven to be the most active.

The work is aimed at solving the problem of neutralization of persistent organic pollutants by catalytic methods. In order to identify the relationship between electronic and steric factors of carbenes with catalytic efficiency in the reaction of hydrodehalogenation of haloarenes, the parameters for estimating the ligand influences are proposed (electronic - Ie indices, Ph philicities, ED electron donicities, and EA electron acceptabilities, steric - dimerization energies) using theoretical methods (DFT, B3LYP5, RHF). Synthesis of new heteroaromatic carbenes of the series of sterically shielded 1,3-diarylphenanthro-[9,10-d]imidazol-2-ylidene, 1,3-diaryl-2-methy­lene­phenan­thro-[9,10-d]imidazoline, tetrahydropyrimidin-2-ylidene, 1,3-diaryl­imidazol-2-ylidene, 1,3,4-triaryl-1,2,4-triazol-5-ylidenes, their carbene complexes with palladium iodide, as well as the carbene complex of the superbasic anionic carbene 1,3-bis-(4-oxidophenyl)-imidazol-2-ylidene with nickel(II) ion. 1H and 13C NMR spectroscopy, mass spectrometry and X-ray diffraction study methods were used to establish the structures of the synthesized compounds. A high catalytic effect of a number of sterically shielded carbene complexes (2.4b, 3.5, 4.6a) in the reaction of hydrodehalogenation of p-dichlorobenzene haloarenes with sodium methoxide in isopropanol at 80 °С (TON 98000–110000) was revealed that can be applied to solve the problem of neutralization of persistent organic pollutants. The efficiency of catalysis by sterically open compounds 4.6b and 6.7 appeared to be low (TON 74, 128). The high catalytic effect of sterically shielded compounds is explained by the increased stability of the complexes under the conditions of an alkaline medium caused by metal alkoxides.

A series of new stable halogenated carbenes, 1-tert-butyl-3,4-diaryl-1,2,4-triazol-5-ylidenes, has been synthesized. According to quantum chemical calculations, 4-(2,3,4-trifluorophenyl)-substituted 1-tert-butyl-3,4-diaryl-1,2,4-triazol-5-ylidene is the least basic in comparison with the known sterically open stable heteroaromatic carbenes. Upon heating in organic solvents these carbenes undergo a tandem induced reaction thereby forming 5-amidino-1,2,4-triazoles. The interaction of carbenes with benzylidenemalononitrile, propanesultone and phenyl isothiocyanate results in zwitterionic compounds of the 1,2,4-triazole series. The data for X-ray diffraction study of 1-tert-butyl-3-phenyl-4-(2,4-difluorophenyl)-1,2,4-triazol-5-ylidene, its protonated salt, complex with copper(i) iodide, related complex of 1-tert-butyl-3-phenyl-4-(2-trifluoromethylphenyl)-1,2,4-triazol-5-ylidene, and adduct of 1-tert-butyl-3-phenyl-4-(4-bromophenyl)-1,2,4-triazol-5-ylidene and propansultone are given.

The book presents the main methods of synthesis used today to obtain organic matter. For students of chemical specialties of universities, as well as graduate students, teachers and researchers.

The electronic properties of carbenes including thermodynamic parameters such as new electronic philicity indices Ie, Ph, and for comparizon chemical hardnesses η, proton affinities (РA) calculated by DFT method (B3LYP5/6-31G*/RHF for definition of electronic indices and B3LYP5/3-21G/RHF, B3LYP5/3-21G/UHF for definition of chemical hard¬nesses) have been discussed in the paper. With their help, the estimation of philicities, electron-donating and electron-withdrawing abilities of a wide range of carbenes of both nucleophilic and electrophilic type was carried out. It was established that the philicities of carbenes according to electronic indices Іе, Ph depend on the carbenic structure (the backbone of the molecule and steric effects of substituents) and also on the reagent structure, particularly its steric effect. For typical nucleophilic carbenes, the Ph is in the range of 1–3,0, for neutral carbenes 1–1,5, IeH 8,5–22,2 eV, for neutral carbenes IeH 8,5–10,5, for typical electrophilic – in the intervals of PhH –0,3–0,5, IeH –3,4–3,4 eV. The intermediate values (Ph 0,5–1,0, IeH 3,4–8,5 eV) are characteristic for typical ambiphilic carbenes. In the evaluation of electron-donating and electron-withdrawing properties, the values of ED and EA should be taken into account (maximal EDH values were found for neutral carbene 20 (13,8 eV) and for superbasic anionic carbenes (for 22 18,4 eV)). The highest electron acceptability EAH was found for cationic carbene 29 (11,8 eV). In the reactions with carbon ions, the values of the IeH, PhH indices decrease significantly, and the electron acceptability increases. Increasing the steric effects leads to «inversion» of philicities for nucleophilic carbenes (Ph up to 0,1), and the properties of electrophilic carbenes become even more pronounced (Ph up to –2,7). The found dependences of the electronic properties of carbenes allow regulating the structure of carbenes to achieve certain characteristics, which together with stability factors can be used in the design of structures for synthesis and practical application.

Carbenes are known to be highly reactive compounds, which can, in turn, spontaneously transform to dimers and products of rearrangements. Therefore, the question about the estimation of stability of carbenes is fundamental in the design of compounds for their subsequent synthesis and application. Aim. To consider the known methods for assessing the stability and stabilization of carbenes, first of all, created by the authors of the article, and show their possibilities in predicting the properties of carbenes. Materials and methods. The study was performed using the DFT method (B3LYP5, 6-311G**, RHF) to estimate the stabilization energies, and the DFT (B3LYP5, 6-31G, RHF) to obtain dimerization energies. Results and discussion. The ways of solving the problem of stability of carbenes by the methods of quantum chemistry are discussed, in particular the application of new criteria for the stabilization of cyclic compounds – energies of the general and cyclic stabilization, energies of non-aromatic conjugations. To assess the possibility of isolating compounds the study of standard dimerization enthalpies (according to the ESP electronic and steric parameter proposed) for different classes of heterocyclic carbenes has been performed taking into account conformational factors. The scale of substituent effects on the stability of carbenes has been developed. It has been shown that sterically shielding substituents cause not only the kinetic stabilization, but also the thermodynamic one. The skeletons of the molecules have been estimated for their degree of influence on the stability of the compounds. Conclusions. The parameters proposed for assessing the energies of the total and cyclic stabilization of carbenes, the dimerization energies of complex carbenes (electronic and steric parameter) allow identifying the most stable structures in the design of compounds for their subsequent synthesis and application.

For carbenes as ambiphilic compounds there is no single scale for estimating their electron properties. Aim. To consider the known methods of estimating the electron-donating and electron-withdrawing properties of carbenes, first of all, created by the authors of the article, and show their possibilities in predicting the properties of carbenes. Materials and methods. The studies were performed using the DFT (B3LYP5/6-311G/RHF) method to estimate proton affinity, DFT (B3LYP5/3-21G/RHF and B3LYP5/3-21G/UHF) to determine chemical hardness and electronic indices. Results and discussion. The electronic properties of carbenes, including thermodynamic parameters, such as proton affinity (PA), chemical hardness η, and new electronic indices Ie, are discussed in the paper. With their help, the electron-donating and electron-withdrawing ability of a wide range of carbenes of both nucleophilic and electrophilic type has been estimated. It has been shown quantitatively that the electronic properties of carbenes depend both on the backbone of the molecule (for example, the type of the heterocyclic nucleus) and on substituents. The above data show the ways of regulating the structure of carbenes to achieve certain characteristics, which together with stability factors can be used in the design of structures for the synthesis and practical application. Conclusions. The author’s results of estimating proton affinity, chemical hardness and electronic indices for the design and use of carbene compounds are considered. Electronic indices have been shown to have some advantages over others for determining the nature (electron-donating and electron-withdrawing) of carbenes.

РЕДАКЦІЙНА КОЛЕГІЯ Б. Д. Грищук -доктор хімічних наук, професор (головний редактор) Я. Г. Бальон -доктор хімічних наук, професор В. С. Броварець -доктор хімічних наук, професор М. В. Вовк -доктор хімічних наук, професор М. І. Короткіх -доктор хімічних наук, професор О. С. Лявинець -доктор хімічних наук, професор В. П. Новіков -доктор хімічних наук, професор М. Д. Обушак -доктор хімічних наук, професор В. І. Станінець -доктор хімічних наук, професор О. П. Швайка -доктор хімічних наук, професор В. С. Барановський -кандидат хімічних наук, доцент

РЕДАКЦІЙНА КОЛЕГІЯ Б. Д. Грищук -доктор хімічних наук, професор (головний редактор) Я. Г. Бальон -доктор хімічних наук, професор В. С. Броварець -доктор хімічних наук, професор М. В. Вовк -доктор хімічних наук, професор М. І. Короткіх -доктор хімічних наук, професор О. С. Лявинець -доктор хімічних наук, професор В. П. Новіков -доктор хімічних наук, професор М. Д. Обушак -доктор хімічних наук, професор В. І. Станінець -доктор хімічних наук, професор О. П. Швайка -доктор хімічних наук, професор В. С. Барановський -кандидат хімічних наук, доцент

The 1-adamantyl substituted stable carbene 5 and the biscarbene 9 of the 1,2,4-triazole series with sterically shielding groups at the position 4 of the heterocyclic ring (dbmp, dipp) have been synthesized in three steps starting from the derivatives of 1,3,4-oxadiazole 1,6. A new method for the preparation of 1,3,4-triaryl-1,2,4-triazol-5-ylidenes (14a-c) has also been proposed and includes the Vilsmeier reaction of 2-benzoyl-1-formylphenylhydrazine with phosphorus chloroxide and aromatic amines, followed by deprotonation of the obtained 1,3,4-triaryl-1,2,4-triazolium salts. The method allows introduction of steric shielding substituents to the 4-position of the heterocycle. The resulting carbenes show promise as nucleophilic catalysts and ligands for carbene complex catalysts of organic reactions.

The present review deals with the syntheses and properties of individual heteroaromatic carbenes of the imidazole, 1,2,4and 1,2,3-triazole series, their fused analogs and mesoionic carbenes including unprecedented structures such as hyperbasic and hypernucleophilic carbenes. Particular emphasis is placed on their physical properties, novel chemical transformations, and catalytic properties.

Highly efficient carbene and polycarbene catalysis of the transesterification reaction of ethyl benzoate in methanol has been observed and results in values of TON as high as 4000 – 6150 at a molar ratio of ester to methanol of 1:18 at room temperature. The most effective catalysts were found to be the individual carbenes or in situ generated carbenes, namely adamantyl and aromatic substituted cyclic compounds and polymeric carbenes. None of the reactions requires the use of molecular sieves. The polymeric imidazol-2-ylidene catalyst was used for the efficient production of biodiesel fuel from sunflower oil.