General and Scalable Synthesis of Diarylhaloarsines From Arsenic Trioxide

Diarylhaloarsines (Ar₂AsX; X = Cl, Br, I) are important intermediates in the synthesis of a wide range of organoarsenic compounds. However, previous methods have long been constrained by limited substrate scope and complex procedures. Herein, we report a practical and general synthetic approach for Ar₂AsX from arsenic trioxide (As₂O₃), an abundant and inexpensive arsenic source. The reaction of aryl Grignard reagents with As₂O₃ affords diarylarsinous acids or diarsine oxides, depending on the steric demand of the aryl substituents. Subsequent halogenation with trimethylsilyl halides proceeds almost quantitatively under mild conditions to produce the corresponding Ar₂AsX. The resulting Ar₂AsX exhibit broad reactivity and can be used in the synthesis of BINAP-type arsenic ligands, reductive formation of diarsines, and nickel-catalyzed coupling reactions for direct aryl group incorporation. This method provides a convenient and scalable route to structurally diverse Ar₂AsX and expands the applicability of these materials as versatile precursors for organoarsenic synthesis.