STUDIES OF DIASTEREOSELECTIVITY IN DIELS-ALDER REACTIONS OF ,8-METHANE-2-(P-TOLYLSULFINYL)-1,4-NAPHTHOQUINONES WITH CYCLOPENTADIENE

The title compounds 6 and 7 have proved to be adequate rigid models to evaluate the ability of the sulfinyl group to control the diastereose lectivity of the [4 + 2] cycloadditions of cyclopentadiene on the ene- dione moiety. The results of thermal and Lewis acid-catalyzed reaction s allowed us to establish that both reactivity and endo / exo selectiv ity were modulated by the presence of the sulfinyl group, the endo-ant i-endo or the exo-anti-endo bisadducts being obtained as major product s depending on experimental conditions. The role of the association be tween the SOTol group and several Lewis acids (BF3 . OEt(2), Eu(fod)(3 ), ZnBr2), which shifted the conformational equilibrium around the C-S bond, was used to explain the stereochemical course of the cycloaddit ions mainly controlled by steric factors. The synthesis of the exo-ant i-endo bisadduct 5 was described for the first time.