Reactivity of 1-boraadamantanes towards bis(trialkylstannyl)ethynes. First examples of 3-boratricyclo[5.3.1.1]dodecanes, and the molecular structure of a tetraalkyldiboroxane

1-Boraadamantane (1) and 2-ethyl-1-boraadamantane (1(2-Et)) react with bis(trialkylstannyl)ethynes (3), R₃Sn-CC-SnR₃ with R=Me (a), Et (b), in a 1:1 molar ratio by 1,1-organoboration under very mild conditions to give the 4-methylene-3-borahomoadamantane derivatives 4a,b and 7a,b, respectively, which are dynamic at room temperature with respect to deorganoboration. The compounds 4a,b react further with 3a,b by 1,1-organoboration to the tricyclic butadiene derivatives 5a,b. Attempts to crystallise 4a afforded the product of hydrolysis, the diboroxane 6a which was characterised by X-ray structural analysis. All products were characterised in solution by ¹H-, ¹¹B-, ¹³C- and ¹¹⁹Sn-NMR spectroscopy.     

Preparation and investigation of the crystals formed in the buckminsterfullerene-tetraselenotetracene-carbon disulfide system

Crystals containing up to 30 wt. % CS₂, according to the data of IR and X-ray photoelectron spectroscopy, were isolated from the C₆₀-TSeT-CS₂ (TSeT is tetraselenotetracene) system. The unusually high concentration of carbon disulfide results in the complete sublimation of the crystals at a relatively high temperature (520 °C). The electron energy loss spectra of the crystals obtained were measured and analyzed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 845–848, May, 1995.This work was financially supported by the Russian Foundation for Basic Research (Projects No. 93-03-18002, 93-03-18705, and 93-03-5650).     

Synthesis and ESR spectra of [4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzosemiquinonato]thallium(i)

[4,6-Di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzosemiquinonato]thallium(i) was synthesized and characterized by IR and ESR spectroscopy. The hyperfine coupling constants with ^203/205Tl nuclei were found to depend strongly on the nature (solvating ability) of solvents. At 298 K, the HFC constant a _Tl changes from 3.09 mT in n-hexane up to 19.70 mT in tetramethylethylenediamine. The coordination number of solvation was found to be 1 for DMF—benzene and pyridine—hexane systems. The thermodynamic characteristics of solvation in the pyridine—hexane system were determined.     

An EPR and molecular mechanics study of radical adducts of phosphonyl radicals with 2-hydroperfluoro-4-methyl-and 4,4-dimethyl-2-pentene

EPR spectra of radical adducts of phosphonyl radicals with 2-hydroperfluoro-4-methyl- and 4,4-dimethyl-2-pentene have been studied. The molecular mechanics method has been used to determine the preferred conformation of the (CF₃)₂CF-CF-HCF₃P(O)(OMe)₂ radical. The eclipsed conformation of the C–P bond and 2p _z -orbital of an unpaired electron is stabilized due to steric factor and hyperconjugation.A. N. Nesmeyanov Institute of Organoelemental Compounds, Russian Academy of Sciences, 117813 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2550–2554, November, 1992.     

Addition of tri(2-methylallyl) borane to 16-dehydropregnenolone acetate

Conclusions The reaction of 16-dehydropregnenolone acetate with tri(2-methylallyl)borane proceeds by 1,2-addition of a boron-allyl fragment to the 20-carbonyl group of the steroid molecule.DeceasedTranslated from Izvestiya Akademil Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1639–1640, July, 1972.     

The Effect of Support Nature and the Temperature of Preliminary Calcination on the Atomic Catalytic Activity of Supported Palladium Catalysts for the Complete Oxidation of Hydrocarbons

It is shown that for palladium catalysts supported on various supports, there is no effect of thermal activation consisting of an increase in the turnover number (TON) of palladium with an increase in the temperature of sample calcination from 500 to 700°C, as was observed in the case of similar supported platinum catalysts; for two palladium–alumina catalysts calcined at 500°C and differing in the concentration of palladium and dispersity, the TON of low-dispersity palladium is substantially higher than the TON of high-dispersity palladium; all other conditions being the same, the TON of supported palladium is determined by the support nature.     

ESR study of spin-adducts of dialkoxyphosphoryl radicals with di(p-methoxyphenyl)methanofullerene

The addition of phosphoryl radicals to C₆₀C(p-C₆H₄OMe)₂ was shown (ESR) to result in the formation of at least seven isomers differing in their hyperfine coupling constants (HFC) with the phosphorus nuclei and in their kinetic behavior and thermodynamic stability.     

Side Chain Functionalization of Lanosterol by Hydroboration and Allylboration: Synthesis of a Ganoderic Acid Analog

A convenient method for the introduction of 23-keto and 26-carboxyl groups (Synthesis of a genoderic acid analog) into lanosterol side chain by use of hydroboration and allylboration as key reactions is described.