Investigations in the field of oxygen-containing heterocycles

In the presence of stannic chloride, 2,3-dichlorotetrahydrofuran adds to isoprene with the formation of 3-chloro-2-(4-chloro-2-methylbut-2-enyl)tetrahydrofuran and to piperylene and bivinyl with the formation, predominantly, of 3-chloro-2-(4-chloropent-2-enyl)- and 3-chloro-2-(4-chlorobut-2-enyl)tetrahydrofuran, respectively, with their allyl isomers. The amount of the latter was estimated from the NMR spectra at 20–30%.For part VII, see [1].     

Investigations in the field of oxygen-containing heterocycles

2-(4-Chloro-2-methyl-2-butenyl)tetrahydropyran and 2-(4-chloro2, 3-dimethyl-2-butenyl)tetrahydropyran react with organomagnesium compounds and also with sodium amalgam with the formation of mixtures of the 2-(2-alkenyl)tetrahydropyrans corresponding to the initial chlorides and the 2-(3-alkenyl)tetrahydropyrans corresponding to the allyl isomers of the initial chlorides. The structure and composition of the products have been established by IR and NMR spectroscopy and by gas-liquid chromatography.For part V, see [1].     

Studies in the field of aromatic heterocycles

An analysis of the PMR spectra of benzo- 2,1,3-selenadiazoles and also of compounds containing 2,1,3-oxadiazole and -thiadiazole nuclei has been carried out. It has been shown that the key atoms O, S, and Se ensure the possibility of the establishment of a ring current in the corresponding heterocycles. Aromaticity in the sense of a strong ring current in these compounds is somewhat weaker than in naphthalene. The estimates were obtained by calculating the difference _{0 ab} of the chemical shifts of the protons of the benzene ring linked to the heterocycle from the experimental spectra (A₂B₂ system) and the subsequent comparison of these data with the theoretical dependence of _{0 AB}on the distance separating the proton under study and the center of the contour of the ring current. In the case of the benzo-2, 1, 3-X-diazoles (X = O, S, Se), this contour is the heterocyclic ring. Direct measurements of the magnetic susceptibility of these compounds have confirmed the considerable equalization of the bonds in the heterocycle, i.e., the participation of the key atoms O, S, and Se in the formation of the ring system of delocalized electrons. It has been shown that the proposed structural scheme permits the prediction of the magnitudes of the chemical shifts and the PMR spectra of such compounds. The question has been raised of the evaluation of the real acceptor properties (electronegativity) of the key atoms completing the heterocycle.For part IV, see [6].     

Pyridine carboxaldehyde-based synthesis of oxygen-containing heterocycles

Heterocycles containing one or two atoms of oxygen are synthesized by the condensation of pyridine carboxaldehydes with ethylene glycol, 1,3-propanediol, and 3-methyl-3-buten-1-ol. When the unsaturated alcohol is used, linear acetals are formed along with the cyclic products.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 801–804, June, 1989.     

Isomerization of oxygen-containing heterocycles in the presence of activated charcoal

Alky1-2,3-dihydrobenzofurans, octahydrobenzofuran, and chromans undergo skeletal isomerization, dehydroisomerization, cis-trans isomerization, and dehydrogenation in the presence of BAU-activated charcoal. An ionic mechanism including initial stripping of a hydride ion from the starting compounds is proposed for the reactions. It is shown by means of ESR spectroscopy that there is no correlation between the catalyst activity and the concentration of paramagnetic centers on it. It is assumed that quinoid groupings on the charcoal surface are the active centers.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 321–323, March, 1975.     

Novel ecdysteroid analogs with oxygen-containing heterocycles in the steroid skeleton

The reaction of ecdysteroids (20-hydroxyecdysone and its acetonides) with lithium in liquid ammonia gave novel analogs with an oxetane 9α,14α-oxacycle in the steroid skeleton. In aqueous alcohol solution the 9,14-oxa analogs rearrange to the more stable 9α,13α-oxa analogs through a 1,2-migration of the 18-Me group from the C-13 to the C-14 atom. Dedicated to Academician B. A. Trofimov in his 70^th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1339–1355, September, 2008.     

Conformation of oxygen-containing heterocycles: Search of the isomerization paths

A method is proposed for the search of the conformational isomerization paths and barriers to interconversion. Use of this method in the study of the ring interconversion ofα-d-glucose gives the minimal barrier for 1C ? C 1 isomerization, which is in agreement with the experimental data.     

Tandem intramolecular Nicholas and Pauson-Khand reactions for the synthesis of tricyclic oxygen-containing heterocycles

[reaction: see text] Simple acyclic enynes can be easily converted into tricyclic ethers upon treatment with Co2(CO)8 followed by Nicholas and Pauson-Khand reactions. Tricyclic [5,8,5]- and [5,7,5]-systems can be prepared in high overall yields in only seven synthetic steps.     

Investigations in the field of aromatic heterocycles

Piazthiole and piazselenole, like benzofurazan, studied previously, are reduced at the dropping mercury electrode with the consumption of six electrons and with the formation of o-phenylenediamine. The transfer of the first electron in acid solutions is preceded by the reversible protonation of the molecules. The ease of reduction rises in the sequence benzofurazan, piazthiole, piazselenole in accordance with a fall, and not with a rise, in the electronegativity of the key heteroatoms O, S, Se and with the decrease in the dipole moments of the corresponding molecules. The presence of two waves in the polarogram of piazselenole is due not to the stagewise nature of its reduction but to the anodic dissolution of mercury in the presence of hydrogen selenide.For part VII, see [1].     

Investigation in the field of aromatic heterocycles

The results of complete quantum-mechanical calculations of the PMR spectra of compounds of the 2, 1, 3-X-diazole (X=S, Se) series are given. The parameters of these spectra have been used previously for a discussion of the aromaticity of the corresponding compounds.For part XII, see [1].     

Studies of the chemistry of heterocycles

In contrast to arylamides of N-benziloyl-p-aminobenzoic acid, the acidochromic cyclization of arylamides of N-benziloylanthranilic acid is accompanied by deamination and, regardless of the nature of the arylamide group, leads to the formation of 7-carboxy-3,3-diphenyl-2-k etoindoline.See [1] for communication LII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 182–183, February, 1972.     

An investigation in the field of aromatic heterocycles

The electronic structures of benzo[c][1,2,5]oxadiazole, benzo[c][1,2,5]thiadiazole, benzo[c][1,2,5]selenadiazole, naphtho[1,2-c][1,2,5]oxadiazole, naphtho[1,2-c][1,2,5]thiadizole, naphtho[1,2-c][1,2,5]selenadiazole, naphtho[2,3-c][1,2,5]oxadiazole, naphtho-[2,3-c][1,2,5]thiadiazole, and naphtho[2,3-c][1,2,5]selenadiazole have been investigated in the -electronic approximation by the Pariser-Parr-Pople method. Molecular diagrams have been calculated and the energies of the first singlet transitions have been calculated. A correspondence has been found between the calculated results and those obtained by experiment (UV spectra, reactivities, etc.).For Communication XVIII, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1473–1478, November, 1973.In conclusion, we express our gratitude to D. A. Bochvar and A. A. Bagatur'yants for a discussion of the results obtained.     

Studies on the chemistry of heterocycles

The mechanism of the aminoalkylation of sodium derivatives of -, -, and -benzolactams is discussed from the point of view of ideas on the formation of cyclic transition complexes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 7, pp. 954–958, July, 1970.     

Investigations in the field of the chemistry of heterocycles

The reaction of 3-aryl-2-chloromethylquinazol-4-ones with secondary amines has given a number of previously unreported 2-aminomethyl-3-arylquinazol-4-ones, and their biological activity has been studied.For part XLV, see [1].     

Studies in the quinone field

The condensation of p-benzoquinone with substituted N-benzyl-β-aminocrotonic esters has been studied. A series of derivatives of 1-benzyl-5-hydroxyindole containing various substituents in the benzene nucleus of the benzyl radical has been obtained.     

Studies in the anthrapyridone field

It is shown that hydrogen chloride catalyzes the replacement of halogen in the reaction of halogenoanthrapyridines with aromatic amines. Cupric acetate, in the presence of potassium acetate at 80–120° C, does not catalyze the replacement of halogen in these substances. The replacement of the arylamino residues in position 6 of a number of 2, 6-diarylaminoanthrapyridines by alkylamine residues under the action of aliphatic amines, was noted.For part V, see [8].