Résumé : The amidinoethylation of amino compounds takes place by the addition of amines to the CC double bond of a variety of N,N'-substituted-propenamidines 1. The most nucleophilic amines such as piperidine, morpholine and pyrrolidine add under very smooth conditions. 1 hr reflux in acetonitrile as solvent and without catalyst. Aliphatic amines such as cyclohexylamine and diisopropylamine require more drastic conditions, higher heating temperature and longer reaction time. Aromatic amines add in the presence of acetic acid, however under these conditions transamidination side reactions are observed. These results illustrate the activation of the CC double bond of propenamidines by the conjugated amidine function thus providing a new class of Michael acceptors for amino compounds. Furthermore the amidinoethylation makes available 3-ammosubstituted-N,N'-substituted-propanamidines 3 not easily accessible by other classical synthetic methods. © 1981.