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].     

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].     

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 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].     

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].     

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.     

Investigations in the chemistry of heterocycles

A method for obtaining 9-phenylacridine-2-carboxylic acid and its ethyl ester from derivatives of 2-aminophenyl(diphenyl)methanol and of 2-oxo-4,4-diphenyl-1,2-dihydro-3,1,4-benzoxazine has been developed.For part XLIV, see [1].     

Investigation of aromatic heterocycles

The results of an analysis of the UV and IR spectra confirm the previously drawn conclusion regarding the aromatic character of 1,2,5-oxadiazole derivatives. The spectral properties of naphth-1,2,5-oxadiazole and phenanthrene are similar; saturation of the double bond between the 4- and 5-carbon atoms of the naphthalene ring disrupts conjugation with the heterocyclic fragment. The introduction of a sulfo group into the 5-position does not substantially change the frequencies and distribution of the IR absorption bands. A difference in the effect of hydroxyl groups in the 7- or 8-positions is revealed. The spectral effects that accompany transition from arene-1,2,5-oxadiazoles to their N-oxides are analyzed.See [1] for communication XIV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1036–1042, August, 1971.     

Research on aromatic heterocycles

Naphthofurazan is reduced in three stages. The anion radical formed in the first one-electron step is recorded by its ESR spectrum. The absence of a one-electron step in the reduction of naphthofuroxan and dihydro derivatives of sulfonaphthofurazan and sulfonaphthofuroxan should be associated with weakening of the aromatic properties of their molecules.     

Research on aromatic heterocycles

The π-electronic structures of the anion and cation radicals of 1,2,5-oxa-, 1,2,5-thia-, and 1,2,5-selenadiazoles and their benzologs were investigated within the framework of the MO LCAO method within the approximation of zero differential overlap by the Pariser- Parr-Pople method for open shells and by the Longuet-Higgins—Pople method (the “half-electron” method). The two methods give close results.     

Studies in the field of oxygen-containing heterocycles

2-Chloro- and 2,3-dichlorotetrahydropyrans add to vinyl acetate in the presence of SnCl₄ with the formation of the corresponding gem-acetoxychlorides. The addition of 2-chlorotetrahydropyran to isopropenyl acetate is accompanied by the splitting out of HCl and the formation of the corresponding substituted enol acetate. The reaction products have been hydrolyzed to aldehydes and ketones.For Communication XIII, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 7, pp. 871–873, July, 1970.     

Investigations in the imidazole field

It has been established that various inorganic and organic bases can be used for the cyclization of 1,2-dialkyl-3-(-oxoalkyl[aralkyl])benzimidazolium halides into derivatives of pyrrolo[1,2-a]benzimidazole. The action of strong bases on quaternary benzimidazolium salts gives O-betaines—intermediates in the closure of the pyrrole ring.For part XL, see [1].     

Determination of substitution sites in monosubstituted five-membered aromatic heterocycles

Similar magnitudes of proton-proton couplings across three, four, and five bonds and proton-carbon couplings across two and three bonds combined with difficult to predict substituent effects make the results of an indiscriminate use of routine (COSY, HSQC, HMBC, etc.) techniques for substitution site determination in C-monosubstituted five-membered heteroaromatics suspect. As demonstrated on two examples of natural products, the use of 1,1-ADEQUATE leads to unambiguous substitution site determination lending thus further support to suggested inclusion of 1,1-ADEQUATE data into computer-assisted structure elucidation (CASE) protocols.     

Investigations in the field of lipids

Summary A method for the separate quantitative determination of the furocoumarins ofFicus carica has been developed.Khimiya Prirodnykh Soedinenii, Vol. 3, No. 5, pp. 295–298, 1967     

Investigations in the field of tetracyclines

Summary The synthesis of 4-N-desdimethyl- (IIa) and 4-N-desmethyl-12a-deoxy-5a,6-anhydrotetracycline (IIb) has been effected.For preliminary communications, see [1].M. M. Shemyakin Institute of the Chemistry of Natural Compounds of the Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 357–363, May–June, 1971. Original article submitted Feburary 26, 1971.