Asymmetric induction in silyl nitronate cycloadditions to Oppolzer's chiral sultam derivatives

Silyl nitronate cycloadditions to Oppolzer's chiral sultam derivatives, followed by the elimination of the silyl alcohols from the resulting N-silyloxyisoxazolidines, provide Δ₂-isoxazolines in good stereoselectivity (ca. 89/11). The favored transition state is suggested in the light of the X-ray crystal structure of a major cycloadduct.