Fig. 4: Substrate scope for nucleophilic ring opening of ABB using aniline as nucleophile; installation of aza-azetidine in marketed drugs, bioactive molecules, and fatty acids.

[a] Reaction condition: 2 (0.2 mmol), aniline (0.4 mmol), TFA (10 mol%), HFIP (0.2 mL), after removal of HFIP add Et3N (0.8 mmol), Boc2O (0.4 mmol), DCM (5 mL).