Electronic interactions in aromatic an heteroaromatic two-ring systems

The chemical shifts of the methyl protons ( ) in the PMR spectra and the integral intensities (A^1/2) of the band of the symmetrical CH stretching vibration of the methyl group in the IR spectra were measured for an extensive series of methyl derivatives of aromatic and heteroaromatic compounds including 3-, 4-, 5-, and 6-substituted 1- and 2-methylnaphthalenes, 4-, 5-, 6-, and 7-substituted 2-methylquinolines, and 5- and 6-substituted 2-methylbenzothiazoles, as well as a number of two- and three-ring systems that do not contain substituents. The changes in the chemical shifts are interpreted with allowance for two principal contributions: the contribution from the ring currents and the contribution from the changes in the electron densities (q) on the H and C atoms of the methyl group. The fact of the existence of a linear relationship between the corrected (for the ring current) values and the calculated (by the CNDO/2 method) electron charges q_C and q_H (the latter plays the dominant role) indicates that the electronic effects of the substituent make the principal contribution to the changes in the shielding constants of the protons of the methyl group in most of the investigated compounds. Similarly, the charges on the H and C atoms of the methyl group convey the trend of the integral intensities of the IR bands, thereby confirming the primarily electronic nature of the effects of structural factors on the A^1/2 values.See [2] for communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 390–396, March, 1979.     

Synthesis and Molecular Structures of (3-Hydroxy, 3-Chloro, 3-Arylamino)-<Emphasis Type="Italic">N</Emphasis>-acetyl-3-arylaminotropones

The structures of 5,7-di(tert-butyl)-2-(5,8-dimethyl-4-piperidinoquinolin-2-yl)-3-hydroxytropone, 5,7-di(tert-butyl)-3-chloro-2-(5,8-dimethyl-4-piperidinoquinolin-2-yl)tropone, 5,7-di(tert-butyl)- 3-(3,5-dimethylphenylamino)-2-(5,8-dimethyl-4-piperidinoquinolin-2-yl)tropone, and 3-(N-acetyl-3,5- dimethylphenylamino)-5,7-di(tert-butyl)-2-(5,8-dimethyl-4-piperidinoquinolin-2-yl)tropone were determined by X-ray diffraction. These compounds were synthesized through a series of transformations, including the nucleophilic substitution of the chlorine atom by piperidine in the starting 5,7-di(tert-butyl)-2-(4- chloroquinolin-2-yl)-3-hydroxytropone followed by the three-step functionalization of the 3-position in 3-hydroxytropone. The nature of dynamic processes in a solution of N-acetyl-3-arylaminotropone associated with the rotation of the N-acetyl group was revealed by the PCM/PBE0/6-31G(d,p) method.     

Phenyl-substituted porphyrins: III. Relative reactivity in the nitration reaction

Study on the nitration of phenyl-substituted porphyrins showed that protonation of the porphyrin macroring does not affect the relative reactivity of the meso- and β-positions and phenyl groups.     

Synthesis and opening of the thiadiazine ring in 6,7-dihydro-5H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines

A reaction of 3-benzylthiotriazole-4-amines with aromatic aldehydes leads to the formation of 6,7-dihydro-5H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines. A dihydrothiadiazine ring opening along the N-N bond occurs by the action of strong bases. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1249–1252, June, 2008.     

Synthesis and structure of 5,7-Di(<Emphasis Type="Italic">tert</Emphasis>-butyl)-2-(8-methanesulfonyloxyquinolin-2-yl)-1,3-tropolone

5,7-Di(tert-butyl)-2-(8-methanesulfonyloxyquinolin-2-yl)-1,3-tropolone whose structure was established by X-ray diffraction analysis and confirmed by ¹H and ¹³C NMR, IR spectroscopy, and mass spectrometry, was obtained by the reaction of 2-methyl-8-methanesulfonyloxyquinoline with 3,5-di(tert-butyl)-1,2-benzoquinone. According to X-ray diffraction study, this sulfonyloxyquinolinotropolone exists in the NH tautomeric form with methanesulfonyloxy group in the exo position to the tropolone ring and the sixmembered chelate ring produced by the quinoline and tropolone moieties stabilized by strong intramolecular hydrogen bond. The strong intramolecular hydrogen bond between the phenolic oxygen atom and the six-membered chelate ring provides supplementary contribution to the stabilization of the NH tautomeric form.