Hydrosilylation reactions of hydrosilatrane and 2-methyl-6-ethyl-1,3-dioxa-6-aza-2-silacyclooctane

Conclusions 1-Hydrosilatrane does not react with monosubstituted ethylenes (or acetylenes) either in the presence of platinum or rhodium complexes or upon initiation of the reactions using organic peroxides, UV irradiation, or thermal methods. By contrast, 2-methyl-6-ethyl-1,3-dioxa-6-aza-2-silacyclooctane readily takes part in hydrosilylation of the indicated unsaturated compounds when Rhacac (CO)₂ is present.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khirnicheskaya, No. 4, pp. 899–901, April, 1986.     

Alkoxy(acyloxy)silanes

Conclusions Alkoxychlorosilanes react with trimethylacyloxysilanes to give the difficultly accessible alkoxy(acyloxy)silanes of general formula (RO)_nSi(OCOR)_4-n (n=1–3) in 60–80% yields.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 671–674, March, 1989.     

Ethynylisopropylgermanes and Their Trimethylsilyl Derivatives

The reaction of ethynylmagnesium bromide with chloroisopropylgermanes (i-Pr_{4 - n} GeCl_{/sub> n} , n = 1-3) was used to prepare previously unknown ethynylisopropylgermanes i-Pr_{4 - n} Ge(CCH) _n (n = 1-3). The reaction of Me₃SiCCMgBr with i-PrGeCl₃ afforded i-Pr(Me₃SiCC)_{3 - n} GeCl _n (n = 1, 2). The reaction of the monochloride with BrMdCCH gave i-Pr(HCC)₂GeCCSiMe₃, while with the dichloride, i-Pr(HCC)·Ge(CSiMe₃)₂ formed. The latter compounds were obtained by independent synthesis from i-PrGe(CCH)₃, EtMgBr, and ClSiMe₃. The reaction of (bromomagnesioethynyl)triisopropylgermane with Me₃SiCl gave i-Pr₃GeCSiMe₃.     

Binulcear polyunsaturated organosilicon dendrimers

Binuclear polyunsaturated organosilicon dendrimers of the zero and first generations, whose central silicon atoms are linked by-CH₂-Ch₂-,-CH=CH-, or-C≡C-bridges, and also containing internal (C≡C) and (CH=CH) groups are prepared. NMR spectra of all the compounds obtained are studied. Their molecular weights were calculated and evaluated experimentally. Key parameters of new dendrimers are presented.     

Reaction of di- and trisubstituted ethynylsilanemagnesium halides with dimethylethynylfluorosilane

Conclusions The reaction of magnesium bromide derivatives of di- and triethynylsilanes with dimethylethynylfluorosilane gave 1,2-disubstituted silylacetylenes containing ethynyl and vinyl groups at the silicon atoms.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2614–2616, November, 1984.     

SKH-1 hairless mice repair UV-induced pyrimidine dimers in epidermal DNA

The SKH-1 hairless mouse strain has been used extensively as a model for human photocarcinogenesis, photoimmunology and photoaging, but little is known about DNA repair in living mouse skin. Mice were irradiated with UV-B light at doses which produce mild to severe sunburn, and the frequency of pyrimidine dimers in epidermal DNA was measured immediately and 6 h after irradiation using T4 endonuclease V treatment and alkaline agarose gel electrophoresis. The results demonstrate significant removal of pyrimidine dimers in mouse skin in vivo, with a dimer half-life of 7.4 h. These findings are similar to the repair of dimers in human skin in vivo. The SKH-1 hairless mouse is thus a useful model for pyrimidine dimer repair in human skin.     

Viability of the antigen determines whether DNA or urocanic acid act as initiator molecules for UV-induced suppression of delayed-type hypersensitivity

UV radiation suppresses the immune response, and UV-induced immune suppression contributes to UV-induced photocarcinogenesis. For UV-induced immune suppression to occur, electromagnetic energy (i.e. UV radiation) must be converted to a biological signal. Two photoreceptors have been identified in the skin that serves this purpose, epidermal DNA and trans-urocanic acid (UCA). Although compelling evidence exists to support a role for each pathway (UV-induced DNA damage or photoisomerization of UCA) in UV-induced immune suppression, it is not clear what determines which photoreceptor pathway is activated. To address this question, we injected UV-irradiated mice with a monoclonal antibody with specificity for cis-UCA or applied liposomes containing DNA repair enzymes to the skin of UV-irradiated mice. The effect that each had on UV-induced suppression of delayed-type hypersensitivity was measured. We asked whether the light source used (FS-40 sunlamps vs solar-simulated UV radiation) altered whichever pathway of immune suppression was activated. Different doses of UV radiation and the viability of the antigen were also considered. Neither the dose of UV nor the light source had any influence on determining which pathway was activated. Rather, we found that the viability of the antigen was the critical determinant. When live antigens were used, UV-induced immune suppression was blocked with monoclonal anti-cis-UCA but not with T4 endonuclease V-containing liposomes. The reverse was observed when formalin-fixed or killed antigens were used. Our findings indicate that antigen viability dictates which photoreceptor pathway predominates after UV exposure.     

Organomagnesium Synthesis of <Emphasis Type="Italic">sec</Emphasis>-Butyl- and <Emphasis Type="Italic">tert</Emphasis>-Alkylchlorogermanes and Their Reaction with Ethynylmagnesium Bromide

The limits of application of organomagnesium synthesis to the substitution of chlorine atoms in tetrachlorogermane with bulky alkyl groups are established. The reaction of tetrachlorogermane with 2-butylmagnesium chloride leads to the substitution of one, two, or three chlorine atoms, yielding the corresponding alkylchlorogermanes (MeEtCH)_nGeCl_4-n . The reaction of GeCl₄ with tert-alkylmagnesium halides leads to the substitution of only one chlorine atom, yielding tert-alkyltrichlorogermanes RMe₂CGeCl₃ (R = Me, Et, Bu). tert-Butyltrichlorogermane reacts with ethylmagnesium bromide to give ethyl(tert-butyl)dichlorogermane. Isopropyltrichlorogermane reacts with tert-butylmagnesium chloride to give isopropyl(tert-butyl)dichlorogermane. This shows that the organomagnesium synthesis does allow linking of two bulky substituents to the germanium atom. The reaction of tert-alkyltrichlorogermanes and 2-butyltrichlorogermane in THF with ethynylmagnesium bromide, in which the hydrocarbon group is the most sterically accessible, allows substitution of all the three chlorine atoms, yielding the corresponding alkyl(triethynyl)germanes. The latter compounds react with the Grignard reagent and trimethylchlorosilane to give the corresponding alkyl(trimethylsilylethynyl)germanes.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 5, 2005, pp. 757–761.Original Russian Text Copyright © 2005 by O. Yarosh, Voronkov, Zhilitskaya, N. Yarosh, Albanov, Korotaeva.