Rare Example of Nucleophilic Substitution at Vinylic Carbon with Inversion: Mechanism of Methyleneaziridine Formation by Sodium Amide Induced Ring Closure Revisited

Intramolecular nucleophilic substitution of the C−Br bond of (E)- and (Z)-2-bromobut-2-enylamines by the pendant nitrogen atom leads to 2-ethyleneaziridines by way of stereochemical inversion at the vinylic carbon atom. The stereochemistry of the products is unambiguously established by X-ray crystallography performed on two derivatives. These cyclizations represent some of the first examples of substitution with inversion in unactivated vinylic substrates. In conjunction with additional deuterium-labeling experiments, the accepted mechanism for this reaction is shown to be flawed.