Efficient synthesis and solid state analysis of 3-(1H-pyrrol-2-yl)quinoxalin-2(1H)-one and 2-(1H-pyrrol-2-yl)-1H-benzo[d]imidazole from pyrrolo-2-ylglyoxyl acid

The synthesis of new pyrrole-functionalized quinoxalines and benzimidazole is described. Our methodology involves the condensation between 2-oxo-2-(1H-pyrrol-2-yl)acetic acid and differently substituted 1,2-phenylene diamines. Depending on the substitution and on the reaction conditions, the synthesis leads to either the pyrrolyl-quinoxaline or -benzimidazole heterocycles. Further insights concerning the structural arrangement of the pyrrolyl-quinoxaline were obtained by solid state analysis, revealing an inverted pyrrole similar to that observed for 2,3-dipyrrolyl quinoxalines. This observation accounts for the fact that strong dipolar interactions or intermolecular H-bonds may govern the structural arrangement in the solid state.