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  • 1
    Electronic Resource
    Electronic Resource
    Head-to-Head versus Head-to-Tail Dimerizations of Transient Silenes - The Solvent-Dependent Regiospecifity of the Dimerization of 2-(2-Methoxyphenyl)-1,1-bis(trimethylsilyl)silene (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1667-1672 
    Details
    ISSN: 1434-1948
    Keywords: Silicon ; Silenes ; 1,2-Disilacyclobutanes ; 1,3-Disilacyclobutanes ; Eliminations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The regiospecifity of the dimerization of the transient 2-(2-methoxyphenyl)-1,1-bis(trimethylsilyl)silene (6), synthesized by base-initiated trimethylsilanolate elimination from (2-methoxyphenyl)[tris(trimethylsilyl)silyl]methanol (5) according to a modified Peterson mechanism, decisively depends on the donating ability of the solvent in which the silene is generated. In ether, 6 undergoes a formal [2 + 2] dimerization to afford 3,4-bis(2-methoxyphenyl)-1,1,2,2-tetrakis(trimethylsilyl)-1,2-disilacyclobutane (12), whereas in toluene the head-to-tail [2 + 2] cyclodimer, 2,4-bis(2-methoxyphenyl)-1,1,3,3-tetrakis(trimethylsilyl)-1,3-disilacyclobutane (13) was obtained. 1,1-Bis(trimethylsilyl)-2-(2,4,6-trimethoxyphenyl)silene (18), similarly made by a modified Peterson reaction, under the same conditions reacted with the eliminated trimethylsilanolate with readdition at the polar Si=C bond to give, after hydrolysis, 2-(2,4,6-trimethoxybenzyl)-1,1,1,3,3,3-hexamethyl-2-(trimethylsiloxy)trisilane (19). A possible mechanism explaining the solvent-dependent regiospecificity of the dimerization of 6 is discussed. The structures of 12 and 13 were determined on the basis of NMR and MS data as well as X-ray structural analyses.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Controlled Conversion of the Transient 2-Mesityl-1,1-bis(trimethylsilyl)silene into a Tetrahydro-2,3-disilanaphthalene, a 1,2-Disilacyclobutane, or a 1,3-Disilacyclobutane (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1083-1088 
    Details
    ISSN: 0009-2940
    Keywords: Silenes ; Silene dimerization ; 1,2-Disilacyclobutanes ; 1,3-Disilacyclobutanes ; 2,3-Disilanaphthalene, tetrahydro- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mesityl[tris(trimethylsilyl)silyl]methanol (1) reacts with strong bases with elimination of trimethylsilanolate according to a Peterson-type mechanism, the outcome of the reaction being dependent on solvent, temperature, and nature of the organometallic base applied. Thus, 1 was converted by treatment with MeLi in ether at -78°C to (E)-1,2,3,8a-tetra -hydro-1-mesityl-5,7,8a-trimethyl-2,2,3,3-tetrakis (trimethylsi-lyl)-2,3-disilanaphthalene (3), formally a [2 + 4] cyclodimer of the transient silene (Me3Si)2Si=CHMes (2). The reaction of 1 with PhMgBr in THF after some days resulted in the formation of (Z)-3,4-dimesityl-1,1,2,2-tetrakis(trimethylsilyl) -1,2-disilacyclobutane (6) as the main product besides small quantities of 3, the polysilane (Me3SiSi(SiMe3)2CH2Mes (10), and the alkoxysilane (Me3Si)3SiCH(Mes)OSi(Si-Me3)2CH2Mes (7). Compound 6, the formal [2 + 2] cycloadduct of 2, can also be obtained by thermal treatment of 3 and is considered to be the thermodynamically more stable silene dimer whereas 3 is the kinetically preferred product. At high LiBr concentrations in the reaction mixture 1 was converted by PhMgBr in THF to (E)-2,4-dimesityl-1,1,3,3-tetrakis(tri- methylsilyl)-1,3-disilacyclobutane (13) besides 6 and [bis(tri-methylsilyl)silyl]mesityl(trimethylsiloxy)methane (11). The unforeseen formation of 13 is discussed as proceeding via the silene-lithium bromide adduct (Me3Si)2Si(Br)CH(Li)Mes (12). In the absence of LiBr 1 was converted by MeLi in THF at -78°C to 11 and the trisilane (Me3Si)2Si(Me)CH2Mes (4b). Probable pathways of the formation of all new compounds are discussed. For 6 and 13 the results of the X-ray structural analyses are given.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951281105
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