Pyrylocyanines. 25 Three-dimensional structures of pyrylo-2-monomethinecyanines and their heteroanalogs

Symmetrical tetra-tert-butyl-substituted pyrylo-2- and thiopyrylo-2-monomethinecyanines were synthesized by the condensation of 2-methyl-4,6-di-tert-butylpyrylium and -thiopyrylium salts, respectively, with 2-(alkylthio)-4,6-di-tert-butylpyrylium and -thiopyrylium salts. The pyrylo-2-cyanine obtained was converted to a tetra-tert-butyl-substituted pyrido-2-monomethinecyanine by treatment with methylamine. It was shown by PMR spectroscopy that, in contrast to pyrido-2-monomethinecyanine, which exists in the E,E form, its oxygen-containing analog exists in the E,Z form, and its sulfur-containing analog exists in the Z, Z configuration.See [1] for Communication 24.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 167–171, February, 1988.     

Pyrylocyanines. 32. Free radicals of a series of tert-butyl-substituted pyrylocyanines and their heteroanalogs

The one-electron reduction of tetra-tert-butyl-substituted pyrylo- and thiapyrylocyanines of the - and -series was investigated by ESR spectroscopy and electrochemistry. The free radicals formed from cations of the indicated dyes were characterized.For Communication 32, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1638–1641, December, 1993.     

Pyrylocyanines. 22. Styrils derived from methoxy-substituted 4-methylflavylium salts

Some methoxy-substituted styrils of the flavylium series have been synthesized. Simple HMO quantum chemical calculations have shown that the terminal rings in these dyes are largely isolated in consequence of the low order of the C₍₄₎-C₍₎ bond. The latter is responsible for and explains the unexpected effects on the positions and widths of the absorption bands consequent upon the introduction of electrondonor CH₃O groups into the heterocyclic nucleus.For Communication 21, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 886–890, July, 1986.     

Pyrylocyanines. 11. Symmetrical tetraphenyl-substituted pyrylo-2-cyanines

Symmetrical polymethine dyes (monomethylidyne, carbo-, and dicarbocyanines), viz., 4,6-diphenylpyrylium, -thiopyrylium, and -pyridinium derivatives, were synthesized. It follows from a comparison of the absorption spectra of pyrylo-2-cyanines and their heteroanalogs with the spectra of the corresponding 4 isomers that these dyes differ from one another with respect to the positions, intensities, and forms of the bands. The pyrylocarbo- and -dicarbocyanines and their sulfur analogs are more deeply colored than their isomers, while the reverse regularity is observed in the pyridocyanine series. The long-wave bands in the spectra of all of the isomers are accompanied by more intensive transitions to the vibrational sublevels than in the case of the isomers.See [1] for Communication 10.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 898–902, July, 1980.     

Pyrylocyanines. 13. Symmetrical pyrylocyanines based on 2,3-polymethylene-4,6-diphenylpyrylium salts

Symmetrical 4,6,4,6-tetraphenyl-substituted pyrylo-2-, thiopyrylo-2-, and pyrylo-2-cyanines in which both positions of the polymethine chain are bonded to the positions of the heterocyclic residues by ethylene and trimethylene groups were synthesized. The introduction of bridged groupings is accompanied by intensification of the fine structure and bathochromic and hypsochromic effects in the absorption spectra; the former effect is greater and the latter effect is smaller in the case of ethylene groups. The steric and electronic effects of these groups are discussed with the aid of PMR spectroscopy and quantum chemistry.See [1] for Communication 12.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1195–1201, September, 1981.     

Pyrylocyanines. 19. Symmetrical pyrylocyanines based on 3,4-polymethylene-2,6-diphenylpyrylium salts

Symmetrical 2,6,2,6-tetraphenyl-substituted pyrylo-4- and thiopyrylo-4-cyanines in which both positions of the polymethine chain are bonded to the positions of the heterocyclic residues by ethylene or trimethylene groups were synthesized. The introduction of bridged groupings gives rise to a bathochromic effect, which is greater for ethylene groups than for trimethylene groups.See [1] for communication 18.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 451–454, April, 1984.     

Aziridinyl ketones and their heteroanalogs

5-Aryl-7-(4-nitrophenyl)-1,4-diazabicyclo[4.1.0]hepta-4-enes (I), which have photochromic properties, were synthesized. The structures of the compounds were confirmed by data from the IR, PMR, and mass spectra. The acidolysis of I was investigated, and it was assumed that the mechanism of the reaction includes diprotonation of the bases, while the primary process is the formation of immonium salts. The structures of the photocolored forms of the salts and bases are discussed.See [1] for communication 1.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 536–540, April, 1979.     

Structure and stability of closo-hexaboranes and their heteroanalogs

The molecular and electronic structures of closo-hexaboranes B₆H₆ ^2–, B₆H₇ ^–, and B₆H₈ and closo-heterohexaboranes XYB₄H₄ (X = Y = CH, N; X = BH, Y = CH^–, N^–, NH, O) were studed by the ab initio (MP2(full)/6-311+G**) and density functional (B3LYP/6-311+G**) methods. The bridging H atoms in closo-hexaboranes B₆H₇ ^– and B₆H₈ can undergo facile low-barrier migrations around the boron cage (the barrier heights are about 10—15 kcal mol^–1). All heteroboranes having octahedron-like structures with hypercoordinated N and O atoms are rather stable and can be the subject of synthetic research efforts.     

Pyrylocyanines. 27. Symmetrical polymethine dyes with an indeno[2,1-b]pyrylium nucleus

A number of symmetrical dyes with an indeno[2,1-b]pyrylium nucleus were synthesized. It is shown that the peculiarities of their absorption spectra are due to the specific characteristics of the condensed heteroring.See [1] for Communication 26.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 605–608, May, 1991.     

Pyrylocyanines. 10. Isobenzothiopyrylocyanines

Polymethine dyes with symmetrical and unsymmetrical structures and 3-phenyl-2-benzothiopyrylium derivatives were synthesized. The color of these dyes is discussed. See [1] for communication No. 9. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 777–782, June, 1980.     

Chemistry of the heteroanalogs of isoflavones. 20. Benzimidazole analogs of isoflavones

3-(2-Benzimidazolyl)chromones with electron-donating and electron-withdrawing substituents and also chromones unsubstituted at position 2 were obtained by the reaction of alkyl--(2-benzimidazolyl)-2,4-dihydroxy-5-acetophenones with carboxylic acid anhydrides and chlorides. Reactions with cleavage and with retention of the pyrone ring were carried out.For Communication 19, see [1].Taras Shevchenko Kiev University, Kiev. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1237–1244, September, 1997.     

Pyrylocyanines. 9. Isobenzopyrylocyanines

Polymethine dyes with symmetrical and unsymmetrical structures, viz., 3-phenyl-2-benzopyrylium derivatives, were synthesized. Their colors are discussed. See [1] for communication 8. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 193–198, February, 1980.     

Chemistry of isoflavone heteroanalogs.

Benzodioxane analogs of chalcones were isomerized to the corresponding flavanones and isoflavones. The PMR and IR spectra of these compounds were discussed.For Communication 11, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 319–323, March, 1989.     

Aziridinyl ketones and their heteroanalogs. 5. Synthesis and structures of 2-aryl-3-aroylaziridines

A number of trans- and cis-isomeric 1-R-2-aryl-3-aroylaziridines were synthesized, and their IR spectra were studied. Intramolecular hydrogen bonding is realized in the trans isomers when R = H, and they exist in the only possible conformation (intermediate between a gauche and a cisoid conformation). cis-Isomers II (R = alkyl) exist in solutions in the form of two conformers, viz., gauche and cisoid conformers, and the gauche conformer is thermodynamically preferable.See [1] for Communication A.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No, 11, pp. 1489–1494, November, 1980.     

Pyrylocyanines. 15. Benzopyrylo-2-cyanines

Symmetrical 4,4-diphenyl-substituted benzopyrylo-2-monomethylidyne, carbo-, and dicarbocyanines and their thio analogs, as well as unsymmetrical carbocyanines that contain, in addition to 4-phenylbenzopyrylium or 4-phenylbenzothiopyrylium rings, 3-ethylbenzothiazolium or 1,3,3-trimethyl-3H-indolium residues, were synthesized. The indicated dyes were more highly colored than their isomers that contain flavylium or thioflavylium residues. On the basis of the deviations calculated from the centers of the absorption bands it was concluded that the benzopyran residues in the dyes of the series have greater electron donor character than those in the dyes of the series.See [1] for communication 14.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1173–1177, September, 1982.     

Pyrylocyanines. 29. tert-Butyl-substituted benzopyrylocyanines

2-tert-Butyl-4-methyl- and 2-methyl-4-tert-butylbenzopyrylium salts, as well as the sulfitr analog of the latter, were synthesized. Polymethine dyes with symmetrical and unsymmetrical structures were obtained from these salts. The factors that affect the color are analyzed.See [1] for Communication 28.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 339–344, March, 1992.     

Pyrylocyanines. 12. Unsymmetrical pyrylo-2-cyanines

Unsymmetrical 4,6-diphenylpyrylo-2- and 2,6-diphenylpyrylo-4-carbo- and -dicarbocyanines, as well as the analogous pyridocyanines containing 3-ethylbenzothiazolium and 1,3,3-trimethyl-3H-indolium residues, were synthesized. The pyrylo-2-cyanines are more deeply colored than the corresponding 4 isomers, and their absorption bands are distinguished by lower intensities and greater widths. On the basis of data on the increase in the width of the absorption bands of unsymmetrical dyes as the length of their polymethine chain increases it is concluded that the -pyran system has greater electron-donor character than the -pyran system. The regularities observed in the pyridocyanine series are just the opposite of these.See [1] for Communication 11.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 903–908, July, 1980.     

Pyrylocyanines. 21. Unsymmetrical α-pyrylo- and α-pyridocyanines

(2-Pyrylo)- and (2-pyrido)(indo)trimethinecyanines containing both electron donor and electron acceptor substituants in the heterocyclic rings have been synthesized. It has been shown that the 4,6-diphenyl-2H-pyran nucleus confers less basicity (electron donor characteristics) than the 1,3,3-trimethylindoline segment. It has also been shown that the introduction of substituents to the heterocyclic residues of unsymmetrical dyes allows one to manipulate their electronic asymmetry over a wide range up to a change in the distribution of charge from one ring to another.For Communication No. 20, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 44–48, January, 1985.     

Character of intermediate radicals in homolytic isomerization of cyclic acetals and their heteroanalogs

Conclusions Employing the EPR method and 2-methyl-2-nitrosopropane as the spin trap, we recorded the formation of the radicals (n = 1 and 2; X = O, N, or a chain composed of C and O atoms; R = H or alkyl) during the photolysis of acetals and their heteroanalogs in the presence of di-tertbutyl peroxide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2097–2099, September, 1976.The authors are indebted to A. Sh. Mukhtarov for assistance in running the experiments.