A general approach to 6-phenylthio-substituted 2, 3, 4, 5-tetrahydro-1H-1, 3-diazepin-2-ones based on the ring expansion reaction of 1, 2, 3, 4-tetrahydropyrimidin-2-ones under the action of nucleophiles has been developed. The first step of the synthesis was preparation of N-[(2-benzoyloxy-1-tosyl) ethyl] urea by three-component condensation of 2- benzoyloxyethanal, urea and p-toluenesulfinic acid. Nucleophilic substitution of the tosyl ...