Improvement on the synthesis of (E)-alk-3-enoic acids

Abstract

(E)-Alk-3-enoic acids have been prepared in high yield (85–90%) and excellent stereoselectivity (98–99%) by a modified Knoevenagel condensation of a straight carbon chain aldehyde with malonic acid, in dimethyl sulfoxide (DMSO) or dimethylformamide (DMF) at 100 °C, in the presence of piperidinium acetate as catalyst. Condensation of the aldehyde with a monoester of malonic acid, under the above conditions, gave the corresponding ester of (E)-alk-3-enoic acid in high yield (76–82%) and good stereoselectivity (90–92%). Condensation of the aldehyde with cyanoacetic acid gave the β,γ-unsaturated nitrile in moderate yield (35–40%) without stereoselectivity.