Functionalized 3,4-dihydropyrimidin-2(1H)-ones (DHPMs, Biginelli compounds) represent a heterocyclic system that has aroused considerable interest of specialists on biologically active materials, drug design and research. We have recently demonstrated an efficient application of a novel synthetic methodology for constructing a pyrimidine ring via the synthon scheme [-C=C-N-]^2-+[-C=N-C=O]²⁺. The bis-electrophilic synthon [-C=N-C=O]²⁺ is furnished by 1-chloroalkyl isocyanates. We studied their reaction with ethyl N-alkyl(aryl)-2-aminocrotonates with the aim to develop a general method for the preparation of N1-substituted dihydropyrimidone derivatives. As found, 1-chlorobenzyl isocyanates 1 react with ethyl 2-aminocrotonates 2 in a methylene chloride solution to smoothly furnish DHPMs 3 in good yields. The most plausible scheme for the reaction between 1 and 2 involves initial isocyanatoalkylation of the nucleophilic carbon atom in enamine 2 to generate intermediates А. Isomeric 2,3-dihydropyrimidin-4(1H)-ones of type 4 are not detected in the reaction mixture thus suggesting complete heterocyclization regioselectivity.