Three-component reaction between triphenylphosphine, dialkyl acetylenedicarboxylates and urea or N-methylurea.

The stabilized phosphoranes, obtained from the three-component reaction between dialkyl acetylenedicarboxylates and urea or N-methylurea in the presence of triphenylphosphine, undergo a smooth reaction in boiling toluene to produce iminophosphoranes in good yields. Under the same reaction conditions, the phosphorane obtained from N-methylurea and dimethyl acetylenedicarboxylate yields methyl 1-methyl-2,6-dioxo-1,2,3,6-tetrahydro-pyrimidine-4-carboxylate.