Cadmium(II) Chloride‐Catalyzed Dehydrative C−P Coupling of Propargyl Alcohols with Diarylphosphine Oxides to Afford Allenylphosphine Oxides

Abstract The cadmium(II) chloride‐catalyzed dehydrative C−P cross‐coupling reaction of propargyl alcohols with diarylphosphine oxides is reported. Several propargyl alcohols including those bearing the sterically demanding tert‐butyl group at the triple bond terminus can be used as good substrates in the reaction to produce the corresponding allenylphosphine oxides in good to high yields in acetonitrile at 100 °C. The reaction can also be easily scaled up to a gram‐scale synthesis. A mechanism study indicates that the reaction may proceed through a process of propargylic substitution to generate phosphonite intermediates followed by [2,3] sigmatropic rearrangement to produce the allenyl products, rather than through a common allenylative substitution resulting from P‐nucleophilicity. magnified image