Reactions of diazoboranes with oxygen enables the synthesis and isolation of dioxaboriranes.

Cyclic peroxides are highly reactive oxygen-containing species that play important roles in chemical synthesis, yet, aside from dioxiranes (R2CO2), well-defined cyclic peroxides of main-group elements remain rare. In particular, cyclic peroxides featuring boron-oxygen frameworks have not been explored. Here we show that boron peroxides can be prepared directly from accessible boron precursors and molecular oxygen under mild conditions. Specifically, reactions of diazoboranes with triplet oxygen afford a family of cyclic dioxaboriranes, including both neutral and anionic variants. These compounds exhibit distinct reactivity: neutral species behave as electrophilic oxygen-atom donors, whereas the anionic analogue is nucleophilic and reacts with carbon dioxide. Computational studies explain why these boron peroxides form thermally, in contrast to dioxiranes that require strict photochemical control. Finally, we show that cyclic dioxaboriranes can be converted into acyclic boron peroxide derivatives, highlighting opportunities for controlling peroxide structure and reactivity at boron.