Substitution effects in intramolecular aziridine–allylsilane cyclizations

We report here the synthesis of an aziridine tethered to a substituted allylsilane via a substituted tether. These tether-substituted aziridine–allylsilanes cyclize differently upon treatment with BF3·OEt2 than tether-unsubstituted aziridine–allylsilanes and provide a 6-endo-type product. We show that steric interactions between the N-substituent of the aziridine and substitution on the tether can control the product distribution.