The reaction of o-phenylenediamine with 3-methylglutaric anhydride

The combination of o-phenylenediamine and 3-methylglutaric anhydride in xylene as solvent produces a complex mixture of products. Isolation and characterization of four products from this reaction has shed some light on the mechanism by which 4-(2-benzimidazolyl)-3-methylbutyric acid ( 1 ) is formed under these reaction conditions.