β‐Elimination of an aziridine to an allylic amine: a mechanistic study

The base‐induced rearrangement of aziridines has been examined using a combination of calculations and experiment. The calculations show that the substituent on nitrogen is a critical feature that greatly affects the favorability of both α‐deprotonation, and β‐elimination to form an allylic amine. Experiments were carried out to determine whether E2‐like rearrangement to the allylic amine with lithium diisopropyl amide (LDA) is possible. N‐tosyl aziridines were found to deprotonate on the tosyl group, preventing further reaction. A variety of N‐benzenesulfonyl aziridines having both α‐ and β‐protons decomposed when treated with LDA in either tetrahydrofuran or hexamethylphosphoramide. However, when α‐protons were not present, allylic amine was formed, presumably via β‐elimination. Copyright © 2011 John Wiley & Sons, Ltd.