Going uphill: A protocol for the smooth conversion of the resistant PO bond in phosphane oxides into a reactive PN bond of synthetically useful pyrazolylphosphonium salts by a highly-charged, oxophilic phosphorus-centered trication is described. The reactions are conducted at room temperature with quantitative yields. We aim towards alternatives to existing reduction methods for phosphane oxide functionalization.

A convenient protocol for the smooth conversion of the resistant PO bond in phosphane oxides into a reactive PN bond of synthetically useful pyrazolylphosphonium salts is described. A highly charged, oxophilic, phosphorus-centered trication is employed and the reactions are conducted at room temperature with quantitative yields. The resulting pyrazolylphosphonium cations are valuable synthetic intermediates and are used for the synthesis of a variety of organophosphorus compounds. This represents a new approach towards the transformation of the rather inert phosphoryl group under very mild reaction and workup conditions and aims towards alternatives to existing reduction methods for phosphane oxide functionalization.