Carbodiphosphorane-Stabilized Parent Dioxophosphorane: A Valuable Synthetic HO2P Source

Introducing a small phosphorus-based fragment into other molecular entities via, for example, phosphorylation/phosphonylation is an important process in synthetic chemistry. One of the approaches to achieve this is by trapping and subsequently releasing extremely reactive phosphorus-based molecules such as dioxophosphoranes. In this work, electron-rich hexaphenylcarbodiphosphorane (CDP) was used to stabilize the least thermodynamically favorable isomer of HO₂P to yield monomeric CDP·PHO₂. The title compound was observed to be a quite versatile phosphonylating agent; that is, it showed a great ability to transfer, for the first time, the HPO₂ fragment to a number of substrates such as alcohols, amines, carboxylic acids, and water. Several phosphorous-based compounds that were generated using this synthetic approach were also isolated and characterized for the first time. According to the initial computational studies, the addition-elimination pathway was significantly more favorable than the corresponding elimination-addition route for "delivering" the HO₂P unit in these reactions.