Lipase catalyzed transesterification of methyl acetoacetate with n-butanol

Keto esters represent an important class of organic building blocks which are used for efficient synthesis of a number of complex natural products. Keto esters are normally produced by chemical catalysis necessitating use of higher temperatures. Alternatively they can be synthesized in non-aqueous media using enzyme catalysis under milder conditions. n-Butyl acetoacetate is an important β-keto ester and its synthesis was studied by transesterification of methyl acetoacetate with n-butanol using supported lipases such as Novozym 435, Lipozyme RM IM and Lipozyme TL IM. Among these enzymes, Novozym 435 was found to be the most active catalyst in toluene as a solvent. The effects of various parameters on conversion and rates of reaction were studied in the absence of mass transfer limitations. A model based on ping-pong bi-bi mechanism was found to fit the initial rate data very well and the kinetic parameters were evaluated by non-linear regression analysis.