Application of a Ferrocene-Based Palladacycle Precatalyst to Enantioselective Aryl-Aryl Kumada Coupling

The palladium catalysed reaction of 1-iodo-2-methylnaphthalene and 2-methyl-1-naphthylmagnesium bromide gave quantitatively an (S-a)-configured cross-coupled product in 80 % e.e. using (R,S-p)-PPFA as a ligand. N,N-Dimethylaminomethylferrocene was cyclopalladated (Na2PdCl4, (S)-Ac-Phe-OH, 93 % e.e., as determined by H-1 NMR as a result of self-induced non-equivalence), and the resulting (S-p)-configured dimeric palladacycle was employed as a precatalyst for this cross-coupling reaction (5 mol%). Addition to the palladacycle of diphenylphosphine and subsequent base-promoted bidentate ligand synthesis and palladium capture gave an in situ generated catalyst resulting in an (S-p)-configured product in up to 71 % e.e.