Mechanism of the Fischer indole synthesis. Quantum-chemical interpretation of the rearrangement of substituted cyclohexanone arylhydrazones to tetrahydrocarbazoles

Calculations of a number of model structures within the scheme of the Fishcer indole synthesis were made on the basis of a bonding variant of perturbation theory in the self-consistent-field (SCF) MO LCAO method. A quantum-chemical interpretation of the effect of substituents on the course of the thermal process is given. The kinetics of the thermal and acid-catalyzed indolization of substituted cyclohexanone arylhydrazones to tetrahydrocarbazoles were studied by spectrophotometry. It was shown that the experimental data are in satisfactory agreement with the calculated values. It was concluded that a concerted mechanism (a [3,3]-sigmatropic shift) for the step involving the formation of a carbon-carbon bond in the Fischer reaction is preferred.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 898–907, July, 1986.     

Effect of annelation on the reactivities of benzoquinolines in hetarylation

The π-electron charges, bond orders, dipole moments, and electronic spectra of benzoquinolines were calculated by the self-consistent-field (SCF) method with allowance for the coulombic repulsion of the electrons; the results of the calculations were in satisfactory agreement with the experimental data. The effect of the position of annelation of the benzene ring on the electronic characteristics of benzoquinolines and their basicities and behavior during hetarylation in the presence of acyl halides was evaluated.     

Reactions of 1,5-diketones

The corresponding 4-ketohydroxanthenes, which undergo methylation and dehydration, are formed in the condensation of cyclohexane-1,2-dione with 2-dimethylaminomethylcyclohexanone, 2-benzylidenecyclo-hexanone, and 2,6-dibenzylidenecyclohexanone. 10a-Hydroxy-1,2,3,4,5,6,7,8,8a,10a-decahydro-4-xanthenone exists in tautomeric relationships with 2,2′,3-triketoperhydrodiphenylmethane.     

Nonlinear power attenuation of the radiation of a pulsed CO2 laser in the atmosphere near the ground

Conclusion Thus, as a result of the natural investigations performed on the propagation of short (microsecond) pulses of CO₂ laser radiation in the near-ground atmosphere, quantitative data are obtained on the nonlinear power attenuation of powerful radiation by the atmosphere in the range of energy densities w = 3–18 J/cm² as a function of the meteorological conditions and the turbulent state of the atmosphere. It has been shown that the principal mechanism of nonlinearity of the medium along a 100–250 m path is the origin of low-threshold optical breakdown centers on solid aerosol particles. The initiation conditions and the main characteristics of an extended laser flash in the atmosphere have been investigated.Future work of interest is to obtain statistically justified dependences of the nonlinear power attenuation and distortions of the structure of beams of powerful pulsed radiation along extended paths on the basic opticometeorological parameters of the state of the atmosphere.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 5–13, February, 1983.     

Cerebrosides of the Far Eastern sponge Hymeniacidon assimilis

Cerebrosides have been isolated from chloroform-ethanol extract of the spongeHymeniacidon assimilis. Their structures have been established with the aid of¹H NMR spectroscopy, acid hydrolysis, and ozonolysis as the -galactosides of the C₁₆-, C₁₇-, and C₁₈-erythro-⁴-sphingenines of normal, iso, and anteiso structures acylated in the amino groups with C₂₁-, C₂₂-, and C₂₃--hydroxy acids. The cerebrosides fromH. assimilis differ in structure from the corresponding compounds isolated previously from sponges.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Institute of Marine Biology, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 634–639, September–October, 1989.