Synthesis of (E,Z)-alpha-Alkylidene-beta-ethoxycarbonyl cyclopentanones 5 a
nd(E,Z)-alpha-alkylidene-gamma-butyrolactones 7 by condensing phosphonates
3 or 6 with a variety of aldehydes in the presence of aqueous potassium car
bonate (6-10M) as base is reported.