Synthesis of Phosphole-2,5-dicarboxylic Acids via a [1,5]-Shift of Carbon Dioxide around the Phosphole Nucleus

A new methodology for the synthesis of 1-P-functionalized phosphole-2,5-dicarboxylic acids is described. The carboxylic group is introduced through a two-step sequence which involves a preliminary attack of the phospholide unit onto CO₂ followed by a [1,5]-shift reaction of the CO₂Li group around the phosphole nucleus. This approach was extended to the preparation of a new type of bidentate ligands.