The invention relates to a process for the synthesis of N-substituted cyclic alkylene ureas by reacting a multifunctional aliphatic amine A having at least two amino groups which may be primary or secondary, at least one of which is a primary amino group, -NH2, and at least one of which is a secondary amino group, >NH, the other hydrogen group whereof having been substituted by a hydrocarbyl group which in turn may be substituted by a hydroxyl group, or an amino group, or a carboxyl group, or a ketone carbonyl group, or a hydrazide or hydrazone group, or a mercaptan group, and at least one further functional group selected from the group consisting of primary or secondary amino groups and hydroxyl groups, and an aliphatic organic carbonate component C selected from the group consisting of dialkyl carbonates CD and of alkylene carbonates CA.
