It has long been known that such compounds as acetoacetic ester, CH3-CO-CH2-COOC2H5, benzoyl aceton C6H5CO-GH2CO-CH3, acetyl acetone CH3-CO-CH2-CO-CH3, acetone dicarboxylic ether C2H5CO-CH2-CO-CH2-CO-C2H3- malonic ester ...