N-aryl methylene benzo-fused sultams (2,3-dihydrobenzo[d]isothiazole 1,1-dioxides) underwent [3+2] cycloaddition with benzonitrile oxide to give 5-spiro isoxazoline adducts with complete regioselectivity. Steric hindrance by atropisomerism around the N-aryl bond induced facial selectivity in these cycloadditions.