Base-Regulated Divergent Synthesis of Acetamides from Dioxazolones and Phosphorus Ylides

In this work, a mild, transition‑metal‑free decarboxylative tandem addition reaction has been developed for the efficient construction of acetamide skeletons. Using bench‑stable and readily storable dioxazolones and commercially available phosphorus ylides as starting materials, the reaction proceeds smoothly at room temperature under an air atmosphere. With Na2CO3 as a weak base, dioxazolones undergo Lossen rearrangement to generate the key aryl isocyanate intermediates in situ, which further undergo addition with phosphorus ylides to afford triphenylphosphine‑substituted acetamides. Upon introduction of BrCF2COOK as a difluorocarbene precursor, cleavage of the phosphine moiety is triggered to achieve divergent transformation toward linear acetamides. Mechanistic control experiments corroborate that aryl isocyanates serve as pivotal intermediates and clarify the full reaction pathway involving difluorocarbene‑mediated phosphine fragmentation. This study establishes a mild, operationally simple, and eco‑friendly one‑pot divergent synthetic strategy for the efficient preparation of two classes of acetamide derivatives, which effectively broadens the scope of tandem reactions between dioxazolones and phosphorus ylides in the construction of amide frameworks.