Cycloadditions of N-Sulfonyl Nitrones Generated by Lewis Acid Catalyzed Rearrangement of Oxaziridines

We have developed cycloaddition reactions of novel, electron-deficient N -nosyl nitrones that arise from the titanium(IV)-catalyzed rearrangement of the corresponding N -nosyl oxaziridines. A diverse range of styrenes and oxaziridines react smoothly in this transformation, producing structurally varied N -nosyl isoxazolidines in good yields and with excellent diastereoselectivity. Importantly, the nosyl protecting group can be easily removed under mild conditions without concomitant cleavage of the sensitive isoxazolidine nitrogen-oxygen bond, allowing efficient access to N -unsubstituted isoxazolidines for further synthetic manipulation and biological evaluation.