Benzimidazoles and related heterocycles 10. A novel acid-catalyzed rearrangement in the system 3-(α-aminobenzyl)quinoxalin-2(1H)-one-ethyl acetoacetate as a simple and efficient method for synthesizing 2-(pyrrol-3-yl)benzimidazoles

A reaction of 3-(α-aminobenzyl)quinoxalin-2(1H)-one with ethyl acetoacetate in boiling acetic acid is accompanied by contraction of the pyrazine ring. A rearrangement involving the fragment C(2)-C(3)-C(NH2)Ph of the quinoxaline system and the fragment C(2)-C(3) of ethyl acetoacetate yields 2-(4-ethoxycarbonyl-5-methyl-2-phenylpyrrol-3-yl)benzimidazole. Possible pathways of this reaction are considered.