Halogenating Reagent‐Triggered Annulation of Propargylic Amides With Carbon Dioxide Leading to 5‐(Halomethylene)Oxazolidine‐2,4‐diones

ABSTRACT The conversion of CO 2 into value‐added chemicals represents a promising strategy for sustainable synthesis. Herein, we report a natural light‐promoted cyclization of propargylic amides with CO 2 using commonly used halogenating reagents as both the reaction promoter and halogen source to access 5‐(halomethylene)oxazolidine‐2,4‐diones, which enables the one‐pot construction of C─O, C─N, and C─X bonds. The protocol accommodates a broad range of substrates, and a variety of functional groups are well‐tolerated under mild reaction conditions, providing access to functionalized oxazolidine‐2,4‐diones up to 92% yield as single E isomers. The mechanistic experiments reveal that the reaction may proceed along two pathways, which are the radical pathway ( Path A ) and the halonium pathway ( Path B ). The resulting 5‐(halomethylene)oxazolidine‐2,4‐diones could be further transformed to complex molecules, highlighting the versatility.