Deoxygenation of phosphine oxides is of great significance to synthesis of phosphorus ligands and relevant catalysts, as well as to the sustainability of phosphorus chemistry. However, the thermodynamic inertness of P�O bonds poses a severe challenge to their reduction. Previous approaches in this regard rely primarily on a type of P�O bond activation with either Lewis/Brønsted acids or stoichiometric halogenating reagents under harsh conditions. Here, we wish to report a novel catalytic strategy for facile and efficient deoxygenation of phosphine oxides via successive isodesmic reactions, whose thermodynamic driving force for breaking the strong P�O bond was compensated by a synchronous formation of another P�O bond. The reaction was enabled by P III /P�O redox sequences with the cyclic organophosphorus catalyst and terminal reductant PhSiH 3 . This catalytic reaction avoids the use of the stoichiometric activator as in other cases and features a broad substrate scope, excellent reactivities, and mild reaction conditions. Preliminary thermodynamic and mechanistic investigations disclosed a dual synergistic role of the catalyst.

The Vilsmeier−Haack reaction is a powerful tool to introduce formyl groups into electron-rich arenes, but its wide application is significantly restricted by stoichiometric employment of caustic POCl 3 . Herein, we reported a catalytic version of the Vilsmeier−Haack reaction enabled by a P(III)/P(V)�O cycle. This catalytic reaction provides a facile and efficient route for the direct construction of C1-deuterated indol-3-carboxaldehyde under mild conditions with stoichiometric DMF-d7 as the deuterium source. The products feature a remarkably higher deuteration level (>99%) than previously reported ones and are not contaminated by the likely unselective deuteration at other sites. The present transformation can also be used to transfer other carbonyl groups. Further downstream derivatizations of these deuterated products manifested their potential applications in the synthesis of deuterated bioactive molecules. Mechanistic insight was disclosed from studies of kinetics and intermediates.

The unique heterocyclic skeletons of N-heterocyclic phosphines (NHPs) endow them with excellent hydridic reactivity, which have enabled a great array of catalytic hydrogenations of unsaturated substrates in the past decades....