Generation and properties of the 1,3-dimethyl-2,4-dioxo-1H,2H,3H,4H-pyrano[4,3-d]pyrimidinium cation in a chloroform–trifluoroacetic acid solution

The 1,3-dimethyl-2,4-dioxo-1H,2H,3H,4H-pyrano[4,3-d]pyrimidinium cation has been prepared by means of acid-catalyzed cyclization of 1,3-dimethyl-6-(2-dimethylaminoethenyl)pyrimidine-2,4(1H,3H)-dione in a chloroform–trifluoroacetic acid solution, and its reactivity towards N-nucleophiles has been determined.