Preparation of new substituted imidazolone derivatives based on 1-(2-oxo-2-phenylethylidene)pyrrolo[3,2,1-ij]quinolin-2-ones

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. The choice of such an N,N-binucleophile as 1,3-dimethylurea allowed us to obtain a number of new 1-(oxoimidazolyl)pyrrolo[3,2,1-ij]quinolin- 2-ones in a process carried out at reflux in acetonitrile and a tenfold excess of 1,3-dimethylurea via p-toluenesulfonic acid catalysis. It has been found that 1-(oxoimidazolyl)pyrrolo[3,2,1-ij]quinolin-2-ones in solution undergo keto-enol tautomerism. This is evidenced by the duplication of characteristic proton signals and the presence of the hydroxyl group proton signal in the region of 4.95 ppm in the 1H NMR spectrum of the obtained compounds. Also, based on the experimental data, we have presented a possible reaction mechanism. It is assumed that the reaction proceeds through consistent intermolecular addition of 1,3-dimethylurea to 1-phenacylidenepyrrolo[3,2,1-ij]quinolin-2-ones with intramolecular cyclization, followed by elimination of a water molecule.