A series of 3-benzoylpyrrolo[2,3-b]quinoxalin-2(4H)-ones, potential bioactive compounds have been synthesized. Their preparation is based on the efficient, regiospecific condensation of o-phenylenediamine with pyrrolidine-2,3,5-trione (1) or its enaminone derivatives, respectively, affording two polymorphic forms of the latter in solid. The NMR spectral assignment of 3benzoylpyrrolo[2,3-b]quinoxalin-2(4H)-ones confirms the presence of only one isomer with enaminone moiety in solution.The quinoxaline-peptide antibiotic family including echinomycin, 1 levomycin and actinoleucin 2 or pyrroloquinoxaline 3, 4 system contains one or more quinoxaline rings, structural unit of several bioactive compounds, exhibiting properties of various types such as antiviral, antibacterial, antifungal, insecticidal and cytotoxic. 5 Synthesis of the pyrrolo[2,3-b]quinoxaline system has been extensively investigated due to a potential pharmacological activity. Its synthesis is readily accomplished by the annelation of ophenylenediamine with 3-chloropyrrolidine-2-one, 6-13 4-oxa-2,10-diazabenzo[b]azulene-1,3,9-trione 14 or pyrrole-2,3-dione 15-21 derivatives, and 3-aminoquinoxaline derivative with diethyl carbonate, 22 respectively.1-Phenyl-4-phenylhydroxymethylidenepyrrolidine-2,3,5-trione (1), 23 used as a building block in our previous investigations on the synthesis of pyrrolo[3,4-x]diazacycloalkadiene 24,25 system, possesses αdicarbonyl moiety susceptible to the double nucleophilic attack, thus seems to be a convenient starting material in the synthesis of the new potential bioactive pyrrolo[2,3-b]quinoxaline derivatives. It is *Dedicated to memory of late Prof. Dr. hab. Wanda Żankowska-Jasińska
