Reaction of 5-formyluracil derivatives 1 with (carbamoylmethy1ene) triphenylphosphorane led to the formation of both the corresponding (2)-and (E)-5-(2-carbamoylvinyl) uracil derivatives 2 and 3. Upon treatment of the 2 isomers 2 with ethanolic sodium ethoxide, a mononuclear heterocyclic rearrangement occurred easily to give 3-(ethoxycarbamoyl) pyridin-6-ones (4) and 3-(N-substituted carbamoyl) pyridin-6-ones (5). Under the ...