Lactone Carboxylic Acids. II. Synthesis of α-Benzylideneparaconic Acids

The reaction of ethyl γ,γ-dialkylparaconate with aromatic aldehydes, i.e., benzaldehyde, anisaldehyde, p-chlorobenzaldehyde, and piperonal, has been investigated. The condensation took place at the α-position of the lactone ring. As the acidic components, α-benzylideneparaconic acids and α-benzylidene-β-alkylidensuccinic acids were obtained in 25-48% and 7-15% yields, respectively. From the neutral portions small amount of ethyl benzylideneparaconates were separated. During the course of distillation ethyl α-benzylideneparaconate was partially converted into α-benzylidene-γ-methy-γ-ethylbutyrolactone.