Examining 1,4,2‐Dioxazol‐5‐One as an Alternative Reagent to Acyl Azides in the Staudinger Reaction

In this study, we explore 1,4,2‐dioxazol‐5‐one as an alternative reagent to acyl azides in the Staudinger reaction, providing a safe and efficient method for synthesizing N‐acyliminophosphoranes under metal‐free conditions. This approach involves a heat‐promoted nucleophilic attack of phosphines on 1,4,2‐dioxazol‐5‐ones, followed by the extrusion of CO2 gas, resulting in the formation of the P−N coupling product. The synthetic utility of this metal‐free imidization of phosphine was demonstrated through a gram‐scale reaction and its suitability for subsequent transformations. Density functional theory (DFT) calculations were employed to elucidate the overall reaction pathway leading to the formation of N‐acyliminophosphoranes. 1,4,2‐Dioxazol‐5‐one serves as a safe and efficient alternative to acyl azides in the Staudinger reaction, enabling the synthesis of N‐acyliminophosphoranes under metal‐free conditions. This method involves a heat‐promoted nucleophilic attack of phosphines on 1,4,2‐dioxazol‐5‐ones, leading to CO2 extrusion and formation of the P−N coupling product. The effectiveness of this metal‐free imidization was demonstrated in gram‐scale reactions and its applicability to subsequent transformations. DFT calculations were used to elucidate the reaction pathway.