Copper(I) complexes of P-stereogenic Josiphos and related ligands

Starting from (R)-Ugi's amine, diastereoselective lithiation followed by Ar'PCl ₂ and then Ar’’MgBr led to the generation, as single diastereoisomers, of (R,S _p,S _phos) [Ar’=Ph, Ar’’=o-Tol] and (R,S _p,R _phos) [Ar’=o-Tol, Ar’’=Ph] PPFA ligand derivatives. Amine substitution of both with HPCy ₂ gave P-stereogenic Josiphos ligands, and then addition of CuCl, the corresponding copper(I) complexes. The latter were also generated by using borane P and N protecting groups and in situ Cu(I) complexation, avoiding the isolation of air-sensitive phosphine intermediates. This protection methodology was also applied to the synthesis of Josiphos/CuCl complexes derived from PCl ₃. In addition, related bulky cobalt-sandwich complex-based derivatives were also obtained. Preliminary investigation revealed isolated CuCl complexes as competent catalyst precursors for enantioselective conjugate addition reactions.