Synthesis and Asymmetric [3 + 2] Cycloaddition Reactions of Chiral Cyclic Nitrone: A Novel System Providing Maximal Facial Bias for both Nitrone and Dipolarophile

Only the convex face of the chiral, cyclic nitrone 1 is accessible to dipolarophiles 2 in [3 + 2] cycloadditions. Since in addition Z2 dictates the orientation of the dipolarophiles by directing the smallest substituent (H) of 2 into the most demanding space, the cycloadducts 3 are obtained with almost perfect stereocontrol.