Abstract Several derivatives of mesoionic imidazo [1, 2-α] pyrimidine-5, 7-dione and 1, 2, 4- triazolo [1, 5-α] pyrimidine-5, 7-dione, two new examples of mesoionic xanthine ring systems, were prepared and characterized. These compounds were conveniently prepared by the condensation of bis-(2, 4, 6-trichlorophenyl) malonates with the appropriately substituted alkylaminoimiazole or 1, 2, 4-triazole.
