Condensation of 4,5-dichloro-1,2-phenylenediamine (I) with 1-phenyl-1,2-propanedione (II) in boiling AcOH provided quinoxaline (III). Subsequent reaction of (III) with ethyl bromopyruvate (IV) led to the pyrroloquinoxaline (V). After reduction of the ester group of (V) to alcohol (VI) with LiAlH4, further oxidation with MnO2 produced aldehyde (VII). This was condensed with boiling 3-(dimethylamino)propylamine (VIII), and the resulting imine (IX) was finally reduced to the target amine with NaBH4 in MeOH. The title compound was finally converted to the dioxalate salt upon treatment with oxalic acid in isopropanol.
The N-arylpyrrole (III) was prepared by the Clauson-Kaas reaction of 2-nitroaniline (I) with 2,5-dimethoxytetrahydrofuran (II) in AcOH under microwave irradiation. Subsequent reduction of the nitro group of (III) using BiCl3 and NaBH4 provided aniline (IV), which was condensed with cinnamoyl chloride (V) in the presence of pyridine to give the corresponding amide (VI). Cyclization of (VI) using POCl3 and pyridine produced the pyrroloquinoxaline (VII), and further Vilsmeier-Haack formylation gave aldehyde (VIII). This was condensed with boiling 3-(dimethylamino)propylamine (IX), and the resulting imine (X) was finally reduced to the target amine with NaBH4 in MeOH. The title compound was finally converted to the trioxalate salt upon treatment with oxalic acid in isopropanol.