This work demonstrates the possibility of obtaining new biologically active molecules containing a privileged imidazolone fragment by the Brønsted acid-catalyzed reaction of 1,3-dimethylurea with 1-(2-oxo-2-phenylethylidene)pyrrolo[3,2,1-ij]quinolin-2-ones. The presence of an active oxoylidene system in ones makes it possible to introduce these compounds into cyclization reactions with various binucleophilic agents.