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

Abstract

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.

Beyond Triphenylphosphine: Advances on the Utilization of Triphenylphosphine Oxide

“…were tolerated (Scheme 19). 28 A plausible mechanism for these transformations was illustrated by the authors (Scheme 19): the lone pair electrons from the amino group of arylurea attacked the positively charged P atom of Hendrickson's reagent in-situ-generated from Ph 3 P(O) and Tf 2 O, and the subsequent release of one molecule of Ph 3 P(O) and successive double deprotonation of the intermediates by the TfO − anion furnished the P�N product. It should be noted that anilines and benzamides failed to react with Ph 3 P(O) and Tf 2 O, perhaps due to their stronger nucleophilicity than N-monosubstituted phenylureas.…”

Simultaneous Formation and Functionalization of Aryliminophosphoranes Using 1,3-Dihydro-1H-benzimidazol-2-ones as Precursors

“…Owning to their synthetic potential, the synthesis and application of iminophosphoranes have attracted considerable attention among organic and medicinal chemists. Since it was first introduced in 1919, the Staudinger reaction between aromatic azides and phosphines has been the most commonly used method for the preparation of aryliminophosphoranes (Scheme a). , Other alternative approaches include the reaction of amines with phosphines in the presence of halogenating agents, azodicarboxylates, or ethylenedicarboxylates (Scheme b), the reaction of ylides with Schiff bases or nitriles (Scheme c), alkylation of aminophosphanes (Scheme d), condensation of N -aryl-2-nitrosoanilines or 2-nitrodiarylamines with triphenylphosphine (Scheme e), as well as condensation of triphenylphosphine oxide with N -monosubstituted arylureas (Scheme f) . These methods have their own merits; however, the preparation of complex iminophosphorane structures often requires a tedious synthetic and purification process involving multistep functionalization which may hinder their practical utility toward challenging targets.…”