Abstract Condensation of 2-butenolide with 5-(4-X-phenyl)-2-furaldehydes (X= H, CH 3, OCH 3, Br, Cl, NO 2) in methanol in the presence of piperidine as catalyst afforded the corresponding 4-[5-(4-X-phenyl-2-furfurylidene)]-2-butenolides. As shown by 1 H NMR spectra, the reaction afforded mixtures of Z-and E-isomers which on crystallization were isomerized to the stable Z-isomers (except when X= NO 2). 4-Bromo-2-butenolide reacted ...