Studies of Diastereoselectivity in Diels−Alder Reactions of (S) S -4a,5,8,8a-Tetrahydro-5,8-methane-2-( p -tolylsulfinyl)-1,4-naphtho- quinones with Cyclopentadiene
1996; American Chemical Society; Volume: 61; Issue: 9 Linguagem: Inglês
10.1021/jo9521209
ISSN1520-6904
AutoresM. Carmen Carreño, J.L.G. Ruano, Antonio Urbano, Miguel A. Hoyos,
Tópico(s)Synthesis and Catalytic Reactions
ResumoThe title compounds 6 and 7 have proved to be adequate rigid models to evaluate the ability of the sulfinyl group to control the diastereoselectivity of the [4 + 2] cycloadditions of cyclopentadiene on the ene-dione moiety. The results of thermal and Lewis acid-catalyzed reactions allowed us to establish that both reactivity and endo/exo selectivity were modulated by the presence of the sulfinyl group, the endo-anti-endo or the exo-anti-endo bisadducts being obtained as major products depending on experimental conditions. The role of the association between the SOTol group and several Lewis acids (BF(3).OEt(2), Eu(fod)(3), ZnBr(2)), which shifted the conformational equilibrium around the C-S bond, was used to explain the stereochemical course of the cycloadditions mainly controlled by steric factors. The synthesis of the exo-anti-endo bisadduct 5 was described for the first time.
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