Woollins’ Reagent is a specialized organophosphorus-sulfur compound used in organic synthesis, primarily for thionation reactions. It facilitates the conversion of P=O bonds to P=S bonds in phosphoryl compounds, enabling the preparation of thiophosphoryl derivatives and phosphorus-containing heterocycles. The reagent is effective for forming P-S and P-Se bonds in various molecules and plays a key role in synthesizing complex organophosphorus structures. Its applications include the development of agrochemicals, pharmaceuticals, flame retardants, and advanced materials such as nanomaterials and semiconductors. Overall, Woollins’ Reagent is a versatile tool for selective transformations in phosphorus chemistry.