Efficient Synthesis of 4‐Halo‐2,5‐dihydro‐1,2‐oxaphosphole 2‐Oxides from 1,2‐Allenylphosphonates and CuX2 and Subsequent Suzuki Cross‐Coupling of the C–Cl Bonds

A convenient and efficient synthesis of 4‐halo‐2,5‐dihydro‐1,2‐oxaphosphole 2‐oxides through CuX2‐mediated direct halocyclization of diethyl 1,2‐allenylphosphonates was developed. The yields range from moderate to excellent. The efficiency of axial‐to‐central chirality transfer has also been studied. Further Suzuki cross‐coupling of the resulting vinylic chlorides with dicyclohexyl(2,4,6‐trimethoxyphenyl)phosphane (LB‐Phos) as the ligand, was established.