The identity of the N-protecting group is key to successful reactivity when using uncommon nitrene precursors, such as carbamimidates, ureas, and guanidines. We found that a 2,2,2-trichloroethoxysulfonyl (Tces) moiety in model substrate 1a serves as a convenient imine protecting group. After optimization of AgNTf2 as the silver salt, a small set of commercially available and custom-synthesized BOX ligands were screened (Table , entries 1-6). While ligands L1-L6 all provided 2a in good-to-excellent yields with exceptional chemoselectivity (only a trace amount of the allylic C-H amination product was observed in the crude mixtures by NMR), the differences in ee were remarkable. L1, which was the optimal ligand in asymmetric aziridinations of carbamates, gave 2a in only 35% ee, while the levels of enantioinduction with L2 and L3 were marginal. We hypothesized that the bulky Tces group could be better accommodated by allowing extra space near the metal center by modifying the BOX ligand scaffold. Indeed, the ee of 2a dramatically increased when indane-based BOX ligands L4-L6 were used, with L5 (entry 1) resulting in optimal enantioselectivity (97% ee) and yield (92%).