No abstract

Reactions of N-fluorobenzenesulfonimide with methylbenzenes, phenols, and phenol ethers were studied under solvent-free conditions. The rate constant ratio for the reactions with mesitylene and durene indicates polar mechanism of the process. Solvent-free fluorination of aromatic compounds with N-fluorobenzenesulfonimide in some cases is more selective than reactions with other N-F reagents in a solvent.Fluorinated aromatic compounds are widely used as pesticides, medicinal agents, and various functional materials; therefore, development of ecologically friendly and selective fluorination procedures seems to be an important problem [1][2][3]. During the past two decades, N-F reagents [1-17] have been extensively used as source of fluorine in mild and selective fluorination of organic compounds. In particular, such reagent is N-fluorobenzenesulfonimide (NFSI) [2,4,[7][8][9][18][19][20][21][22][23][24]. It is nonhygroscopic, stable to storage, and convenient to handle with. N-Fluorobenzenesulfonimide is quite reactive, but at the same time it exhibits a moderate oxidative ability [2], which is important for fluorination of organic compounds with low oxidation potentials. N-Fluorobenzenesulfonimide is commonly used to effect fluorination of carbanions, enolates, and enol ethers in the synthesis of fluorinated intermediate products necessary for the manufacture of medicinal agents [7][8][9]. Direct fluorination of aromatic compounds with NFSI was performed less frequently than with other N-F reagents, e.g., 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane salts .The goal of the present work was to study the selectivity in fluorination of aromatic compounds, namely methyl-substituted benzenes, phenols, and phenol ethers, with NFSI in the absence of a solvent. The selectivity problem in electrophilic fluorination under these conditions remains poorly studied (cf. [22]).We have found that the yield of monofluoro derivatives in the fluorination of polymethylbenzenes

No abstract

With the use of Hartree-Fock and DFT methods we demonstrated that for the benzene derivatives with the substituents Me, Et, Pr, i-Pr, t-Bu, CF 3 , F, and Cl π-complexes are more favorable by energy, whereas with the substituents CHO, MeCO, PhCO, CN, NO, and NO 2 n-complexes are more feasible. The affi nity of aromatic compounds to the nitrosonium-cation (A NO +) at the formation of the π-complexes grows with the growing donor character of the substituents in the ring and with their number. The best agreement between the calculated and experimental A NO + values for benzene was obtained with the use of RI-MP2/L1 method.Nitrosonium complexes of aromatic compounds are intensively investigated for many years [1][2][3][4][5][6][7][8][9][10][11]. The interest in these compounds originate from their participation as intermediates in a number of important organic reactions like diazotization, C-nitrosation, and nitration via the nitrosation of aromatic compounds [12,13]. It was established that the NO + cation catalyzed the bromination of aniline derivatives [14] and the proton exchange in N,N-dimethylanilinium-ion [15] ascribing these facts to the formation of the corresponding complexes arene-NO + . The interest to the studies of the nitrosonium complexes grew as the unique role of the NO molecule in the in vivo processes was discovered [1,16]. It is presumed that the nitrosonium-cation and some molecules being its sources take part in the processes of neurotoxic and neuroprotective actions of nitrogen oxide [17], and also are involved in the reactions resulting in DNA cross-linking [18]. Inasmuch as the experimental measurement of the aromatic compounds affi nity to the nitrosonium-cation (A NO +) is a complicated problem [1,19,20] it is interesting to apply the quantum-chemical methods to the calculation of A NO + values.The goal of this study is the theoretical investigation of the effect of structural factors on the complex formation of NO + cation with monocyclic aromatic compounds and establishing the features of the structure of the nitrosonium complexes.The following aromatic compounds we have chosen as the objects of the study: benzene (Ia) and its derivatives C 6 H 5 X Ib-Io, and also compounds II-VII. The choice of the objects of the study took into consideration the existence of the experimental data on the affi nity of the aromatic compounds to the NO + cation and the presence of spectral and XRD data supporting the formation of the nitrosonium complexes [1,[4][5][6].Quantum-chemical calculations were carried out by the methods DFT/PBE/3z [21] and RI-MP2/L1 [22] applying the program package PRIPODA [23], and also by Hartree-Fock (RHF) [24] and B3LYP [25] methods using GAMESS software [26]. The calculations were performed with the complete optimization of the geometry of all molecular structures corresponding to the stationary points, and the corrections for the zero vibration level to the total energy of the species also were taken into account. The electronic correlation was accounted for by the Møller-Pl...

While there is a body of experimental data concerning dimers formed by an aromatic molecule and its radical cation, information on the corresponding dimer radical anions (DRAs) is scarce. In this work, evidence for the formation of the DRAs of decafluorobiphenyl and 4-aminononafluorobiphenyl has been obtained by the optically detected electron paramagnetic resonance and the time-resolved magnetic field effect techniques. Theoretical investigation (DFT B3LYP-D3/6-31+G*) of these DRAs and the DRAs of octafluoronaphtalene and 1,2,4,5-tetrafluorobenzene previously detected by Werst has been undertaken to gain greater insight into the structure of the polyfluoroarene DRAs. Without substituents different from a fluorine atom, an extra electron is evenly delocalized over two fragments; the bonding interaction is π stacking. On the potential energy surfaces (PES), there are two minima of nearly equal energy corresponding to the structures of perfect and parallel displaced sandwiches. Such a PES structure is due to a conical intersection between two electronic states of different symmetry. The DRA of 4-aminononafluorobiphenyl is an ion-molecular associate stabilized by electrostatic interactions involving NH 2 groups. The complex cyclic structure of the PES of this DRA suits the successive electron transfers between the dimer fragments. The calculated hyperfine coupling constants averaged over the PES minima agree well with the experimental ones.