The method for making a phosphorus ylide produces the ylide 2,3-bismethoxycarbonyl-4-phenyl-5-arylhydrazono-cyclopenta-1,3-dienyl-triphenylphosphonium in pure form by simple recrystallization of the reaction product. 3-Oxo-3-phenyl-2-(arylhydrozono)propanal and dimethylacetylenedicarboxylate are mixed in dichloromethane at room temperature. After cyclization of the intermediate (preferably at least two hours), triphenylphosphine is added to the mixture, ultimately resulting in formation of 2,3-bismethoxycarbonyl-4-phenyl-5-arylhydrazono-cyclopenta-1,3-dienyl-triphenylphosphonium. The product is recrystallized to produce 2,3-bismethoxycarbonyl-4-phenyl-5-arylhydrazono-cyclopenta-1,3-dienyl-triphenylphosphonium in pure form and in high yield. The aryl group may be any aromatic or aliphatic group.