Uracil-BX-Enabled O-Uracilylation to Access 5-Aryloxy Uracils via Umpolung Strategy

Herein, we report a mild protocol for the synthesis of structurally diverse and biologically relevant 5-aryloxy uracil derivatives via umpolung O-uracilylation of phenols using a bench-stable uracil-containing cyclic iodine(III) reagent, Uracil-BX. The transformation proceeds with remarkably short reaction times under base-mediated conditions at room temperature, enabling the easy transfer of the uracil moiety to a broad range of phenol derivatives in moderate to high yields. Unlike previously reported acyclic uracil iodonium salts, Uracil-BX is self-stable, easy to handle, and avoids the need for transition metals or external oxidants. Furthermore, we performed reaction kinetics and complementary DFT studies to gain detailed insights into the reaction mechanism. This method represents the foremost example of phenolic O-uracilylation using a cyclic hypervalent iodine reagent, expanding the synthetic utility of Uracil-BX scaffolds in nucleobase transfer chemistry.