The preparation of trans-2,3-disubstituted indolines from 1-azido-2-allylbenzene derivatives via a diastereoselective radical cascade using ethyl iodoacetate and triethylborane is described. Further lactamization afforded substituted benzopyrrolizidinones with excellent diastereomeric ratios. The radical cascade/lactamization sequence was efficiently applied to the synthesis of a 3-oxo-leucomitosane related to the mitomycin family of alkaloids.