Abstract: | The reaction of aceturic acid p-nitrophenyl ester with active methylene compounds Y-CH2-CO2R has been found to give either the normally expected C-acylation compounds 2 (Y = -CN, -CO2R, -COCH3) or N-acetyl-α-Y-substituted tetramic acids 3 (Y = -CO2R,-COCH3), depending on the reaction conditions. Moreover, the intramolecular condensation of the C-acylation compounds 2 derived from malonic and acetoacetic esters (Y = -CO2R, -COCH3) to α-Y-substituted tetramic acids is shown to proceed through initial cyclization to the corresponding N-acetyl-α-Y-substituted tetramic acids 3 (Y = -CO2R, -COCH3). |