Copper‐Catalyzed C−P Cross‐Coupling of (Cyclo)alkenyl/Aryl Bromides and Secondary Phosphine Oxides with <i>in</i> <i>situ</i> Halogen Exchange
Paweł Woźnicki, M. Stankevič
Abstract
Abstract An efficient protocol for concurrent tandem halogen exchange/C−P cross‐coupling of cycloalkenyl bromides and secondary phosphine oxides has been developed. The catalytic system is based on cheap and air‐stable copper(I) iodide as the precatalyst, commercially available N,N’ ‐dimethylethylenediamine as the ligand, and Cs 2 CO 3 or K 2 CO 3 as the base. The use of sodium iodide as an additive reduces the excessive use of organic bromides to near‐stoichiometric by promoting the in situ transformation to the corresponding iodides. Diarylphosphine oxides undergo cycloalkenylation with 35–99 % yields and dicyclohexylphosphine oxide with 30–53 % yields. In the case of acyclic alkenyl bromides the cross‐coupling products undergo conjugate addition of diphenylphosphine oxide and satisfying yields are observed only for internal olefins. In the case of aryl bromides satisfying yields (43–72 %) are observed only for sterically unhindered arenes or arenes possessing an ortho ‐directing group. Cycloalkenylphosphine oxides prepared in the cross‐coupling reaction undergo base‐catalyzed and base‐promoted conjugate addition to give bis(phosphinoyl)cycloalkanes.