A convenient method for conversion of the Z-isomer to the E-isomer from a mixture containing both isomers of fulgides

A new method for the conversion of the Z-isomer of unsymmetrical substituted bis-methylenesuccinic anhydrides, ‘fulgides’, to their geometrical E-isomers was achieved by heating the Z-isomer under reflux or a mixture of both isomers in pyridine to give the E-isomer in near quantitative yield.