Metal-Free Aerobic Radical Ring Opening–Cyclization of Bicyclo[1.1.0]butylamides to Oxazolidin-4-ones

Bicyclo[1.1.0]butane (BCB) is a highly strained compound with unique reactivity. In this work, we discovered that a BCB derivative bearing an aryl and a diisopropylamide group undergoes an oxygen-mediated transformation to give the corresponding oxazolidin-4-one derivative in good yield under mild conditions (EtOAc, O₂, 40 °C). The structure of the product was confirmed by X-ray crystallographic analysis, and radical trapping experiments suggested that the reaction involves a radical pathway. This reaction enables direct conversion of BCB carbon atoms into a heterocyclic scaffold with a high atom economy.