Synthesis of Functionalized Stable Phosphorus Ylides. New Synthesis of Dimethyl (Z)-2-{2-(ethoxycarbonyl)-1-cyclopentenyl}-2-butenedioates

Ethyl 2-oxo-1-cyclopentanecarboxylate undergoes a reaction with dialkyl acetylenedicarboxylate in the presence of triphenyphosphine to produce stable phosphorus ylides in good yields. These ylides undergo intramolecular Wittig reaction in boiling toluene to produce cyclobutene derivatives, which undergo ring-opening reactions to produce dialkyl (Z)- 2-{2-(ethoxycarbonyl)-1-cyclopentenyl}-2-butenedioates.