Nitrosonium complexes of [2.2]paracyclophane

The reaction of [2.2]paracyclophane with nitrosonium tetrachloroaluminate was studied by NMR (¹H, ¹³C) spectroscopy using deuterium isotopic perturbation technique. The resulting cationic complexes containing one and two nitrosonium ions are involved in fast (on the NMR time scale) interconversion. Quantum-chemical calculations performed on the DFT level (using triple zeta basis set) indicate the higher stability of 2η single-charged π-complexes relative to σ complexes corresponding to the addition of NO⁺ ion at the ipso and ortho positions. The formation of the single-charged π-complex is energetically more favorable, compared to the double-charged π-complex. The affinity of NO⁺ for [2.2]paracyclophane is much greater than for p-xylene, presumably due to stacking interaction between the aromatic rings in the π-complex.     

Nitrosonium complexes of 2,11‐dithia‐5,6,8,9‐tetramethyl[32](1,4)cyclophane: a combined experimental and theoretical study

¹H and ¹³C NMR studies and quantum chemical calculations show the interaction between 2,11‐dithia‐5,6,8,9‐tetramethyl[3₂](1,4)cyclophane and nitrosonium cation to result in the formation of π‐ and n‐complexes. According to DFT/B3LYP/6‐31G(2d,p) calculations, formation of nitrosonium complexes is a strongly exothermic process both in gas phase and in SO₂. Affinity of single‐charged complexes to NO⁺ is usually larger than that of double‐charged and triple‐charged complexes, affinity of all the charged complexes to nitrosonium cation in SO₂ being larger than that in gas phase. The π‐complex with nitrosonium cation coordinated to the methylated aromatic ring is the most stable with structural characteristics being close to those obtained by X‐ray diffraction for nitrosonium π‐complexes of hexamethylbenzene and other arenes. The N―O bond lengths in all the complexes are quite close to each other and larger than that in NO⁺ cation. The S―N bond length increases upon transition from single‐charged to double‐charged and polycharged complexes. Copyright © 2014 John Wiley & Sons, Ltd.     

Electrophilic Amination of Methylbenzenes with the System NaN3-AlCl3-HCl. Effects of the Solvent,Crown Ether,and Substrate Structure

Using mesitylene and o-xylene as examples, it was shown that the solvent nature strongly affects the conversion of methylbenzenes in electrophilic amination with the system NaN₃-AlCl₃-HCl. Two-parameter correlations were found between the substrate conversion, on the one hand, and dielectric constant and number of heavy atoms in the solvent, on the other. A considerable solvent effect on the regioselectivity of amination of o-xylene was observed. The presence of 18-crown-6 weakly affects the ratio of isomeric amines, but the conversion of o-xylene sharply decreases. Solid aromatic substrates, such as durene and pentamethylbenzene can also be involved in electrophilic amination with the system NaN₃-AlCl₃-HCl. On the basis of the experimental data and the results of quantum-chemical calculations, participation of a nitrenium intermediate in this reaction was postulated.     

Fluorination of Bi- and polycyclic aromatic hydrocarbons with <Emphasis Type="Italic">N</Emphasis>-fluorobis(phenylsulfonyl)amine in the absence of solvent

Reactions of N-fluorobis(phenylsulfonyl)amine with naphthalene, 1-methylnaphthalene, phenanthrene, anthracene, and pyrene without solvent were investigated. Sometimes the fluorination of aromatic compounds with N-fluorobis(phenylsulfonyl)amine without solvent proceeded more selectively than at the use of fluorinating reagents in solution.     

Generalized structural and kinetic relationships for 1,2-shifts of a hydrogen atom in carbocations and neutral compounds

Dynamic PMR has been used in a kinetic study of degenerate rearrangement of 5,6-X₂-1-H-1, 2-dimethylacenaphthylenonium ions (X=CH₃, Br), accomplished by means of a 1,2-shift of the hydrogen atom. It has been found that the free energy of activation of the 1,2-shift of the H atom in the 5,6-X₂-1-H-1,2-dimethylacenaphthylenonium cation (X=H, CH₃, Br), in the 1-H-1,2-dimethylcyclopentyl cation, and in 5-H-1,2, 3,4,5-pentamethyl-1,3-cyclopentadiene exhibits a linear correlation with parameters characterizing the electron density on the atom to which the migrant is shifted.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1352–1358, June, 1991.     

Nitrosonium complexes of fluorene and 9,9-dimethylfluorene

The reaction of fluorene and 9,9-dimethylfluorene with nitrosonium tetrachloroaluminate was investigated using ¹H and ¹³C NMR spectroscopy with deuterium perturbation. The arising positively charged complexes with one and two nitrosonium cations are involved into an interconversion fast in the NMR time scale. The data of quantum-chemical calculations performed by DFT method (basic Λ02) indicate the higher stability of single-charged π-complexes of 2η type compared with the π-complexes corresponding to the addition of two NO⁺ cations. In the dication π-complexes the transoid position of the NO groups is more favorable than the cisoid position.     

Nitrosonium complexes of triptycene

According to the ¹H and ¹³C NMR data, triptycene reacts with nitrosonium tetrachloroaluminate to form positively charged π-complexes with one and two nitrosonium ions, which are rapidly (on the NMR time scale) converted into each other. DFT quantum-chemical calculations with Λ02 basis set indicated higher stability of singly charged complexes relative to doubly charged. Addition of three nitrosonium ions to triptycene molecule is unfavorable from the energy viewpoint.     

D/H isotope effects in π-complexes of deuterated hexamethylbenzenes with the nitrosonium cation

The isotope effects of deuterium, manifested in the¹³C NMR spectra of complexes of deuterated hexamethylbenzenes C₆(CD₃)_n·(CH₃)_6–n with the nitrosonium cation, have been studied. The small values observed for the isotopic perturbation are evidence of -bonding of the NO⁺ group the hexamethylbenzene molecule. The applicability of an additive scheme of calculation of isotope effects for the ring carbon atoms of the complexes, based on the increments of replacement of the CH₃ group by CD₃ in hexamethylbenzene, has been demonstrated.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, 630090 Novosibirsk. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2104–2109, September, 1992.