68260-21-9Relevant academic research and scientific papers
Reactivity of the Silaethene Ph2Si=C(SiMe3)2
Wilberg, Nils,Link, Matthias
, p. 1231 - 1240 (2007/10/03)
Silaethene Ph2Si=C(SiMe3)2 (3), generated as a reaction intermediate by the thermal elimination of LiX from Ph2SiX-CLi(SiMe3)2 (X = Br, F) or by the thermal cycloreversion of the cycloadduct of 3 and Ph2C=NSiMe3, forms adducts 3*donor, the stability of which increases in the order of donor = Et2O according to an ene reaction, with a=b (e.g.CH2=CHOMe; Ph2C=NSiMe3) or a=b=c (e.g. (t-Bu)2RSiN3, R = Me, t-Bu) or a=b-c=d with or or cycloaddition.The following order of relative reactivity of trapping reagents for Ph2Si=C(SiMe3)2 was found: Ph2CO > (t-Bu)2MeSiN3 > butadiene > 2,3-dimethylbutadiene > Ph2CNSiMe3 > (t-Bu)3SiN3 > anthracene.Summing up, it may be said that going from Me2Si=C(SiMe3)2 to Ph2Si=C(SiMe3)2 there is only a gradual but not principal change of silaethene reactivity.This change is due to increasing polarity and overcrowding of the double bond, that is increasing Lewis acidity and steric hindrance of the unsaturated silicon atom.Certainly, the former silaethene stabilizes thermally by dimerization, the latter by isomerization. - Keywords: Adduct formations, insertions, ene reactions, -, -, -cycloadditions of Ph2Si=C(SiMe3)2 ; Reactivity order of traps ; Reactivity of Me2Si=C(SiMe3)2 and Ph2Si=C(SiMe3)2
Thermal Stabilization of the Silaethene Ph2Si=C(SiMe3)2
Wiberg, Nils,Link, Matthias
, p. 1241 - 1250 (2007/10/03)
Silaethene Ph2Si=C(SiMe3)2 (3) (generated from Ph2SiBr-CLi(SiMe3)2 = 3*LiBr in Et2O at -78 deg C) reversibly isomerizes fast by methyl migration, then a bit slower by phenyl migration, and finally fast by methyl migration into thermodynamically more stable Me2Si=C(SiMePh2)(SiMe3) (3a), then into medium stable PhMeSi=C(SiMe2Ph)(SiMe3) (3b), and finally into most stable Me2Si=C(SiMe2Ph)2 (3c) (cf.Schemes 1 and 2; Figure 1).Simultaneously with isomerization 3a -> 3c cycloadditions (dimerizations) of 3a and 3c occur (formation of 3a * 3a, 3a * 3c, 3c * 3c; cf.Scheme 2).Over and above that, silaethenes 3a and 3c irreversibly isomerize into disilaindanes 4a, 4b, and 4c (cf.Scheme 6).Certainly, the latter reactions are even slow at 100 deg C.Thermolysis of 3a * 3a, 3a * 3c, 3c * 3c at 340 deg C, on the other hand, leads by way of cycloreversion and the intermediate formation of an equilibrium mixture of 3, 3a, 3b, 3c almost quantitatively to 4.In addition to the thermolysis products mentioned above, products of 3 and its isomers 3a, 3b, 3c with the solvents (for example Et2O; cf.Scheme 7), with the silaethene sources (for example 3 * LiBr; cf.Scheme 8), or with products formed from sources besides silaethene 3 (for example Ph2C=N-SiMe3; cf.Scheme 4) are observed. - Keywords: Methyl and phenyl group migrations in Ph2Si=C(SiMe3)2 ; Silaethenes Me2Si=C(SiMePh2)(SiMe3), PhMeSi=(SiMe2Ph)(SiMe3), Me2Si=C(SiMe2Ph)2 ; Silaethene dimers ; Disilaindanes ; Silaethene reactions with Et2O and with Ph2SiBr-CLi(SiMe3)2 ; Insertions of silaethenes into SiN bond of Ph2C=N-SiMe3
Generation and Detection of the Silaethene Ph2Si=C(SiMe3)2
Wiberg, Nils,Link, Matthias,Fischer, Gerd
, p. 409 - 418 (2007/10/02)
Bromotrisilylmethanes (Me3Si)2(Ph2XSi)CBr (4-13; Table 1) are formed by the reaction of (Me3Si)2(Ph2HSi)CM (M = Li, Na) with bromine or with bromine/chlorine (X = H, Cl, Br) and also by treating (Me3Si)2(Ph2BrSi)CBr with KHF2 (X = F), H2O or MeOH (X = OH, OMe), MeLi (X = Me), BuLi/Br2 (X = Bu), PhLi/Br2 or PhLi/PhOLi/Br2 (X = Ph, OPh).PhLi, BuLi, and tBu3SiNa convert the bromotrisilylmethanes by Br/M exchange into compounds (Me3Si)2(Ph2XSi)CM, which may be protolyzed, alkylated, and brominated .For X = halogen the equilibrium (Me3Si)2(Ph2XSi)CM Ph2Si=C(SiMe3)2 (3) + MX exists.Thereby, silaethene 3 is formed in Et2O at -78 deg C (X/M = Br/Li) or at room temperature (X/M = F/Li, Br/Na), respectively, reversibly in low concentrations and at higher temperatures irreversibly (formation of secondary products of 3).The intermediacy of 3 has been established chemically by trapping 3 with (for example) RLi (formation of insertion products in the R-Li bond), Ph2C=NSiMe3 (formation of a cycloadduct, which may serve as a source of 3), tBu2MeSiN3 (formation of a cycloadduct), and particularly 2,3-dimethyl-1,3-butadiene (formation of Diels-Alder and ene reaction products).In the last case products and yields are independent of the origin of 3.From Me2Si=C(SiMe3)2 (1) to 3 there is only a gradual (but no principal) change of silaethene reactivity (3 is more Lewis acidic than 1). - Keywords: Silaethenes/ Bromotris(silyl)methane derivatives
Photochemically generated silicon-carbon double-bonded intermediates. 13. The formation and reactions of 1,2-disilacyclobutanes
Ishikawa, Mitsuo,Kovar, Dieter,Fuchikami, Takamasa,Nishimura, Kunio,Kumada, Makoto,Higuchi, Taiichi,Miyamoto, Setsuro
, p. 2324 - 2328 (2007/12/18)
The photolysis of 1-(trimethylsilylethynyl)-1,1-diphenyl-2,2,2-trimethyldisilane in the absence of a trapping agent afforded 1,1,2,2-tetraphenyl-3,4-bis[bis(trimethylsilyl)methylene]-1,2-disilacyclobutane (6). This compound could be transformed photochemically or thermally into 1,1,2,24etraphenyl-3-[bis(trimethylsilyl)ethenylidene]-4,4-bis(trimethylsilyl)- 1,2-disilacyclobutane (8). 1,2-Disilacyclobutanes 6 and 8 reacted with m-chloroperoxybenzoic acid to give the corresponding 1-oxa-2,5-disilacyclopentane derivatives. Thermolysis of 8 gave 1,1,3,3-tetraphenyl-2-[bis(trimethylsilyl)ethenylidene]-4,4-bis(trimethylsilyl)- 1,3-disilacyclobutane (10) and 1,1-dimethyl-2-[bis(trimethylsilyl)ethenylidene]-3,3-diphenyl-4,4- bis(phenyldimethylsilyl)-1,3-disilacyclobutane (11) in a ratio of 1:1. Thermolysis of 8 in the presence of anthracene afforded a 1:1 adduct of anthracene and 1,1-diphenyl-4,4-bis(trimethylsilyl)-1-silabutatriene in addition to 1,3-disilacyclobutane 10. When 8 was thermolyzed in the presence of a small excess of methanol, both 1,1-diphenyl-4,4-bis(trimethylsilyl)-1-silabutatriene and 1,1-diphenyl-2,2-bis-(trimethylsilyl)-1-silaethene were trapped by methanol. On heating 8 with elemental sulfur, a 1-thia-2,5-disilacyclopentane was produced. Preliminary results of an X-ray diffraction study of 11 are also described.
REACTION OF TRIS(TRIMETHYLSILYL)METHYLSILICON HALIDES WITH METHANOLIC SODIUM METHOXIDE. PROBABILITY OF SILA-OLEFIN INTERMEDIATES
Eaborn, Colin,Happer, Duncan A.R.,Safa, Kazem D.
, p. 355 - 362 (2007/10/02)
The compounds TsiSiR2X react with boiling 2 M MeONa-MeOH to give products of the type (Me3Si)2CHSiR2OMe.It is suggested that the reaction proceeds through an elimination, analogous to E2 eliminations of alkyl halides, involving synchronous attack of MeO- at an Me3Si group, liberation of X-, and formation of (Me3Si)2C=SiR2.The compounds TsiSiPhMeF and TsiSiPhCl2 react analogously to give (Me3Si)2CHSiPhMe(OMe) and (Me3Si)2CHSiPh(OMe)2 .The compounds TsiSiMe2OMe and TsiSiMe3 do not react, while TsiSiMe2H gives TsiH.The compound TsiSiCl3 reacts with 0.1 M MeONa-MeOH to give the substitution and elimination products TsiSiCl2(OMe) and (Me3Si)2CHSi(OMe)3 in ca. 1/2 ratio.
