In this vein, we discovered recently that arylpyrrolidinosquaramide catalyst 1a induces highly enantioselective addition of bromide to oxetanes activated either by protonation or silylation (Figure ). An electrostatic potential map of 1a in its computed reactive conformation reveals a highly asymmetric dipolar active site featuring an anionbinding domain (blue) and cation-binding domain (red) (Figure ). These domains define an internal electric field organized about a helical axis, thus presenting a chiral environment defined by electrostatic preorganization and a plausible framework for enantioinduction in both mechanisms. To assess the potential generality of this recognition mechanism, we considered whether the electrostatic recognition exhibited by 1a might enable highly stereocontrolled additions to azetidinium ions, substrates with structural and functional features quite distinct from activated oxetanes. Here we report the successful application of catalyst 1a to the enantioselective ring opening of structurally and functionally diverse 3-substituted azetidines to afford synthetically useful bifunctional αamino-γ-halopropane chiral building blocks (Figure ).