Effet de solvant sur support solide:régiosélectivité de l'alkylation des énolates de l'acétylacétate d'éthyle par le sulfate d'éthyle en présence de “hmpt solide”

The reaction of Li, Na, K enolates of ethylaceto acetate with diethylsulfate in THF at room temperature gives 60–70% O-alkylation when performed in the presence of one molar equivalent of solid HMPA. Without HMPA, in the same conditions, Li enolate docs not react, Na enolate only gives C-alkylation while K enolate leads to 90% C-alkylation, the reactions being quite slower in the two latter cases. The effects of one molar equivalent of solid and liquid HMPA are compared: for the K enolate the reaction is faster and the degree of O-alkylation higher with solid HMPA; practically no difference is seen for Na enolate, while the reverse is observed with the Li enolate. The cooperative effect of the polymer should thus only work for a sufficiently large cation, as the Li enolate is fixed on the solid HMPA in a larger amount than the K enolate. The study of this reaction is proposed to test the efficiency of other “solid solvents” interacting strongly with cations.