Recyclization of 5-Ethoxycarbonylpyrimidines Occurring with Substitution of a Carbon Atom in the Heterocycle by an Exocyclic Carbon Atom

Abstract

Among isomerization recyclizations of pyrimidines, the best studied have been the Dimroth [1] and Kost–Sagitullin [2-4] rearrangements. They occur as a result of substitution of the ring nitrogen atom in the α-position of the pyrimidine by an exocyclic nitrogen atom (in the first case) or carbon atom (in the second case), which leads to formation of a pyrimidine or pyridine ring respectively. This report is devoted to study of yet another recyclization transformation of a pyrimidine ring accompanied by substitution of a carbon atom in the heterocycle by a non-ring carbon atom, which from the type of substitution that occurs can be called C–C recyclization. We have shown that upon brief boiling in aqueous solution of base, the substituted 4-amino-5ethoxycarbonylpyrimidines 1a-c rearrange to form the 5-carbamoyl-4-hydroxypyrimidine derivatives 2a-c. The recyclization described proceeds via substitution of the C(4) atom of the ring by a non-ring carbon atom of the ester group.