Hybrid Density Functional Theory (DFT) calculations for multiple conformers of the insertion reactions of a methylenecyclopropane into the Ti−C bond of two differently α‐substituted titanaaziridines explain the experimentally observed differences in regioselectivity between catalytic hydroaminoalkylation reactions of methylenecyclopropanes with α‐phenyl‐substituted secondary amines and corresponding stoichiometric reactions of a methylenecyclopropane with titanaaziridines, which can only be achieved with α‐unsubstituted titanaaziridines. In addition, the lack of reactivity of α‐phenyl‐substituted titanaaziridines as well as the diastereoselectivity of the catalytic and stoichiometric reactions can be understood.