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

The conversion of CO2 into value-added chemicals represents a promising strategy for sustainable synthesis. Herein, we report a natural light-promoted cyclization of propargylic amides with CO2 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.