Copper-Catalyzed Radical Dearomative Azidation: Synthesis of Cyclic α-Quaternary α-Amino Phosphonic Acid Precursors from 2-Phosphonyl-3-Hydroxybenzothiophenes/Benzofurans

We herein describe a Cu(II)-catalyzed synthesis of cyclic α-quaternary α-amino phosphonic acid precursors from 2-phosphonyl-3-hydroxybenzothiophenes/benzofurans via radical dearomative azidation with azidotrimethylsilane in the presence of <i>tert</i>-butylhydroperoxide as an oxidant. This method exhibits mild reaction conditions, broadens substrate scope (up to 96% yields), enables gram-scale synthesis, and allows further derivatization, providing an efficient approach to valuable cyclic α-quaternary amino phosphonic acid precursors with potential applications in medicines and pesticides.