220265-30-5Relevant articles and documents
Adducts of sila-, germa-, and stannaethenes Me2E=C(SiMe3)2 (E = Si, Ge, Sn) with anthracene: Syntheses, structures, thermolyses
Wiberg, Nils,Wagner, Susanne,Vasisht, Sham-Kumar,Polborn, Kurt
, p. 1412 - 1420 (2007/10/03)
The [4 + 2] cycloadducts of Me2E=C(SiMe3)2 (E = Si, Ge, Sn) and anthracene are prepared by reaction of an excess of anthracene in benzene with the [2 + 2] cycloadduct of Me2Si=C(SiMe3)2 and Ph2C=NSiMe
On the Reactivity of Germaethene Me2Ge=C(SiMe3)2: Mechanistic Aspects of Diels Alder and Ene Reactions [1]
Wiberg, Nils,Wagner, Susanne
, p. 838 - 850 (2007/10/03)
Diels-Alder and ene reactions of germaethene Me2Ge=C(SiMe3)2 (2) with butadienes >C=C + (Combining vertical line above)-C + (Combining vertical line above)=CC=C + (Combining vertical line above)-CH butadiene; 2-methylpropene > propene), and retarded by an increasing bulkyness of substituents in 1.4- or 1,3-positions (e.g. 1-methylbutadiene > 2-methylbutadiene; 1-vinylpropene > propene). It is concluded from these studies that Diels-Alder and ene reactions of 2 occur - like those of Me2Si=C(SiMe3)2 (1) or of ethenes >C=Ca concerted way and are HOMOdiene-LUMOdienophile and HOMOene-LUMOenophile controlled. Thus 2 and 1 behave as carbon analogues. With regard to a specific diene or ene (e.g. anthracene: toluene), 2 is the better dienophile or enophile than 1 or ethenes. With a fixed diene/ene mixture (e.g. butadiene/propene), 2 acts as the better dienophile, while 1 is the better enophile. These results can be explained by the π/π*-energy difference and the double bond polarity decreasing in the direction 1 > 2. Only cis-piperylene gives a [2+2] cycloadduct with 2, besides two [4+2] cycloadducts, and an ene reaction product.
