Sustainable Transesterification of β-Ketoesters Catalyzed by Amine Grafted on Silica Gel

Abstract

Transesterification of β-ketoesters with various alcohols has been effected by N,N-diethylaminopropylated silica gel (NDEAP) as a catalyst in refluxing xylene. Generality of the reaction was demonstrated by successful transesterification of olefinic alcohols, tertiary alcohols and alcohols having acid- or base-sensitive substituents. The catalyst has been efficiently recycled more than five times without any re-activation.

Keywords

transesterification - β-ketoester - amine catalyst - silica gel support

References

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6

NDEAP was prepared according to the same procedure as ref.^5b, using N,N-diethyl-3-aminopropyl(trimethoxy)silane and silica gel. Nitrogen loading was 0.72 mmol/g according to combustion analysis.

7

Typical Experimental Procedure: To a stirred solution of menthol (2a, 156 mg, 1 mmol) and methyl acetoacetate (1a, 130 µL, 1.2 mmol) in anhyd xylene (4 mL) was added NDEAP pellets (279 mg, 0.72 mmol/g, 0.2 mmol) and the resulting mixture was heated at reflux for 7 h. After removal of the catalyst by filtration, the filtrate was evaporated to dryness to give a residue, which was purified by column chromatography on silica gel to give β-ketoester 3a (238 mg, 99%). The catalyst NDEAP was re-used intact for the subsequent reaction.