Abstract
Stable crystalline phosphorus ylides were obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of 2,3di-hydroxybenzaldehyde and 2-hydroxy-4-methoxybenzal-dehyde. These stable ylides exist in a solution as a mixture of two geometrical isomers as a result of the restricted rotation around the carbon-carbon partial double bond resulting from the conjugation of the ylide moiety with the adjacent carbonyl group.