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Reaktivität des Silaethens Ph 2 Si=C(SiMe 3 ) 2
Author(s) -
Wiberg Nils,
Link Matthias
Publication year - 1995
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19951281215
Subject(s) - chemistry , reactivity (psychology) , adduct , medicinal chemistry , stereochemistry , reagent , cycloaddition , catalysis , organic chemistry , medicine , alternative medicine , pathology
Reactivity of the Silaethene Ph 2 Si=C(SiMe 3 ) 2Frühere Mitteilungen: Lit.Herrn Prof. Dr. Herbert Schumann zum 60. Geburtstag gewidmet. Silaethene Ph 2 Si=C(SiMe 3 ) 2 ( 3 ), generated as a reaction intermediate by the thermal elimination of LiX from Ph 2 SiX‐CLi(SiMe 3 ) 2 (X = Br, F) or by the thermal cyclore‐version of the [4 + 2] cycloadduct of 3 and Ph 2 C=NSiMe 3 , forms adducts 3 donor, the stability of which increases in the order of donor = Et 2 O < Br − < THF < NEtMe 2 < F − , and combines with the reactants a‐b (e.g. R – Li; R = H, Me, n Bu, Ph) with insertion into the a‐b bond, with a=b‐c‐H [e.g. O=C t Bu‐CH 2 ‐H; CH 2 =CR‐CH 2 ‐H, R = Me, CMe=CH 2 , CH 2 SiPh 2 CH(SiMe 3 ) 2 ] according to an ene reaction , with a=b (e.g. CH 2 =CHOMe; Ph 2 C=NSiMe 3 ) or a=b=c (e.g. t Bu 2 RSiN 3 , R = Me, t Bu) or a=b‐c=d [e.g. CH 2 =CR‐CR=CH 2 , R/R = H/H, Me/Me, Me/CH 2 SiPh 2 CH‐(SiMe 3 ) 2 ; Ph 2 C=Y, Y = O, NSiMe 3 ] with [2 + 2] or [3 + 2] or [4 + 2] cycloaddition . The following order of relative reactivity of trapping reagents for Ph 2 Si=C(SiMe 3 ) 2 was found: Ph 2 CO > t Bu 2 MeSiN 3 > butadiene > 2,3‐dimethylbutadiene > Ph 2 CNSiMe 3 > t Bu 3 SiN 3 > anthracene. Summing up, it may be said that going from Me 2 Si=C(SiMe 3 ) 2 to Ph 2 Si=C‐(SiMe 3 ) 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 rilicon atom. Certainly, the former silaethene stabilizes thermally by dimerization, the latter by isomerization.