Research on imidazo[1,2-a]benzimidazole derivatives. 25. Reaction of 2,9-disubstituted imidazo[1,2-a]benzimidazoles with acrylic acids and their derivatives

The substitutive addition of acrylic acids and their esters, amides, and nitriles to 2,9-disubstituted imidazo1,2-a]benzimidazoles, which leads to 3-(imidazo1,2-a]benzimidazol-3-yl)propionic acids and their derivatives, was studied. The rate of addition depends on the structure of the unsaturated compound, the nature of the substituent in the 2 position, the magnitude of the charge on the carbon atom in the 3 position of the heteroring, and the reaction conditions. The addition proceeds most smoothly in polyphosphoric acid (PPA). In the case of acrylonitrile imidazo1,2-a]benzimidazol-3-ylpropionic acid amides were isolated in PPA. In the reaction of - or -substituted acrylic acids with 2-phenylimidazo1,2-a]benzimidazoles in PPA, in addition to the corresponding imidazo1,2-a]benzimidazol-3-ylpropionic acids, products of their intramolecular cyclodehydration at the ortho position of the phenyl substituent are formed.See 1] for Communication 24.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1496–1502, November, 1987.