C- and N-cyanoacetylation of 6-aminopyrimidines with cyanoacetic acid and acetic anhydride

A series of 6-aminopyrimidines are cyanoacetylated with a mixture of cyanoacetic acid and acetic anhydride. When pyrimidin-4(3H)-ones are used as substrates, the substitution occurs at C-5, however, when the substrates are substituted pyrimidines at the C-2 and C-4, the cyanoacetylation takes place at the exocyclic amino group.