The reaction between primary amines and 2-bromo-2-(cycloalkylidene)acetates in alcohol under high pressure provides the expected spiroaziridines in good yields and diastereomeric excesses. With bulky or aromatic amines, this reaction competes with the migration of the double bond, which, migrating from an exo to an endocyclic position, provides an intermediate allylic α-bromo ester, immediately converted