An Approach to P=N Bond Formation: Straightforward Synthesis of Arylurea-Derived Phosphazenes via Condensation of Ph3P=O with N-Monosubstituted Arylureas

The Hendrickson's reagent-mediated formation of the P=N bond provides access to arylurea-derived phosphazenes compounds using readily available N-monosubstituted arylureas and Ph3P=O. Various functional groups were tolerated to give arylurea-derived phosphazenes in the yield of 71-93%. The reaction also provides an alternative strategy for constructing compounds containing P=N bond. In this transformation, the Hendrickson's reagent unprecedented selectively reacts with the free amine group instead of the oxygen atom of N-monosubstituted arylurea. In addition, we found that thioureas could act as an effective thionating agent by converting Ph3P=O to Ph3P=S.