The conversion of an aziridine plus an iminium salt to a 1,2-diamine

The conversion of an aziridine to a 1,2-diamine using lithium iodide and an iminium salt is discussed. We have found that when the aziridine is substituted by only alkyl groups, it is the less substituted carbonnitrogen bond that is broken; whereas, when the aziridine is substituted by a phenyl group at either the nitrogen or the carbon, it is the more substituted carbonnitrogen bond that is broken. For a 2,3-disubstituted aziridine, the reaction sequence goes with net retention of stereochemistry.