One hundred years of Meldrum’s acid: advances in the synthesis of pyridine and pyrimidine derivatives

A general review (138 references) focused on the recent advances in the application of Meldrum’s acid reactivity for synthesis of diverse pyridine and pyrimidine derivatives, mostly small and drug-like molecules is presented.     

CO<Subscript>2</Subscript> laser oscillating in the range of 16 μm

The ability of a CO₂ laser to oscillate in the range of 16 (14) μm at room temperature was investigated experimentally and theoretically. The output energy per pulse was ~60 mJ at peak power of ~50 kW. It was necessary to minimize not only harmful losses but also useful ones in both channels 00⁰1–02⁰0 and 02⁰0–0110 and to increase the input energy, i.e., the density of free electrons in the discharge, in order to increase the peak power and energy of 16-μm radiation. The highest values of peak power and energy of radiation were reached at different pressures of the active mixture. The rotational bottleneck effect limiting the peak power and energy of oscillation was important at rather low pressures of the active medium. Oscillation at the R12 line is more preferable than that at the P12 line for use as 9.6-μm dumping radiation.     

Temperature dependence of associative equilibria of DMSO according to raman scattering spectra

Raman scattering spectra of dimethyl sulfoxide (DMSO) are studied in the area of the line corresponding to symmetric CSC stretching vibrations of the molecule. It is established that this line is composed of a low-frequency component that corresponds to the vibrations of monomeric molecules and a high-frequency component that corresponds to the vibrations of DMSO dimers. Values of self-association equilibrium constants K _a varying in range from 0.20 (23°C) to 0.081 (100°C) are obtained. Since the intensities of the respective components of the line contour are proportional to the compound’s concentrations, the enthalpy of DMSO self-association (ΔH = ?11.7 ± 0.9 kJ/mol) is determined from the temperature dependences.     

Insect pheromones and their analogues XLVIII. A convenient synthesis of the 10E,12Z- and 10E,12E- isomers of hexadecadien-1-ol and of hexadeca-10E,12Z-dienal — Components of the sex pheromone of the silkworm moth

The 10E,12Z- and 10E,12E- isomers of hexadecadien-1-ol and of hexadeca-10E,12Z-dienal — components of the sex pheromone of the silkworm mothBombyx mori — have been synthesized from the readily available octa-2E,7-dien-1-ol.     

Remote detection of sulfur dioxide by means of a CO2 laser

The possibility of remote detection of SO₂ in the 9-μm region of the spectrum by means of a TEA CO₂ laser was theoretically and experimentally investigated with regard to the real state of the atmosphere and the contribution of background concentrations of H₂O, CO₂ and NH₃ to absorption. For sounding along short paths (2L=2 km), the method of detection of small concentrations of SO₂ (at the MPC level) with the use of the lines of the CO₂-molecule regular transitions (00^o1–02^o0 band) has been devised and experimentally tested. It is shown that in sounding along longer paths (2L=6 km), a noticeable increase in sensitivity can be achieved by the generation lines of the CO₂-molecule sequential 00^o2–02^o1 band. B. I. Stepanov Institute of Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 508–515, July–August, 1998.     

Hydroalumination of alkenes by the LiAlH4 · 3AlBr3 system

The hydroalumination of a series of alkenes and some fused aromatic hydrocarbons by the LiAlH₄ · 3AlBr₃ system in low-polar solvents was studied. Alkenes with mono-, di-, tri-, and tetraalkyl substituted, mono- and diaryl substituted double bonds and anthracene react at room temperature to give the corresponding dibromoaluminoalkanes in high yields. Benzylidenefluorene, tetraphenylethylene, naphthalene, and phenanthrene do not undergo hydroalumination under these conditions. Camphene, bicyclo[3.2.1]oct-2-ene, and norbornene afford the corresponding organoaluminum compounds with high stereoselectivity. Oxidation and halo- and acyldemetallation of the resulting alkyl- and arylalanes were carried out.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1637–1642, September, 1993.