The synthesis of β-keto esters has been performed in good yield by reacting excess methyl acetoacetate with barium oxide, acylating the resulting barium complex with acid chloride, and then cleaving the r-acyl β-keto ester with methanol at a mild temperature. Using this new procedure, various β-keto esters were prepared. Thus, methyl 4-phenyl-3-oxobutanoate, methyl 3-phenyl-3-oxopropionate, methyl 4-cyclohexyl-3-oxobutanoate, and methyl 3-oxooctadecanoate were prepared from methyl acetoacetate and the corresponding acid chloride in 69%, 84%, 67%, and 74% yields, respectively. β-Keto esters are known to be useful as intermediates in the synthesis of drugs, ceramides, biodegradable polymers, etc., and there have been reported a number of syntheses for β-keto esters. 2 For example, recently, Benetti et al. 2d reviewed the synthesis of β-keto esters. In this review, numerous procedures were reported; in particular, the acylation of an acetoacetic ester at the C2 carbon, a well-known process, was discussed in detail. As the base component to be employed in this acylation process, NaH, NaNH 2 , or alkali metal alcoholates are usually used. 3,4 However, the achieved yields are only of the order of 30-40%, because the β-keto ester formed during the condensation reaction has a higher reactivity than the starting compounds to be converted, which can lead to numerous secondary reactions. As an improvement in the base component in the reaction for condensing