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.