Origin of the reactivity differences of substituted aziridines: CN vs CC bond breakages

Aziridines are broadly used as starting materials for various chemical syntheses, and the underlying reactions (CN vs CC bond breaking accompanied by an attack of a nucleophile or a dipolarophile) are strongly influenced by the substitution pattern. The present study investigates reaction courses of possible ring-opening reactions accompanied by the attack of a nucleophile for different substitution patterns of the aziridine. Information is obtained through the computation of the underlying potential energy surfaces and reaction paths. The results provide insight into the mechanisms of different ring-opening reactions and explain how the kinetics and thermodynamics of the reaction are influenced by substituents. This allows predicting substitution patterns that steer the reaction course to either CN or CC bond cleavage.