Ring-opening reactions of some 1-ethoxycarbonylaziridines with acetic acid in cyclohexane

Abstract

The formation of N-(2-acetoxylalkyl)carbamates by acetolysis of 1-ethoxycarbonylaziridines in cyclohexane follows an A-2 mechanism where the rate is first order in the aziridine and second order in acetic acid. The regiospecificity of the formation and the reactivity can be interpreted by an A-2 mechanism where bond-breaking is more advanced than bond-making, so that these properties are controlled by electronic factors (a so-called borderline A-2 mechanism). However, an A-2 mechanism largely governed by steric hindrance of initial attack and strain relief on opening, respectively, is proposed for cis-aziridines with bulky substituents at 2- and/or 3-positions. N-Allyl-carbamates formed in some cases appear to result from an A-1 mechanism.