Exploring stereogenic phosphorus: The search for new chiral diphosphines

The synthesis of P-stereogenic ligands bearing 2,6-disubstituted phenyl gro ups at the P atom is a challenging problem. The results reported herein hel p define the scope and limitations of the existing synthetic protocols, suc h as Juge's oxazaphospholidine borane method and the enantioselective depro tonation of P(BH3)(CH3)(2)(R) developed by Evans and Imamoto. Juge's new ap proach based on chlorophosphine boranes was exploited for the preparation o f a C-1 -symmetric MiniPhos-like ligand. Preliminary results concerning the application of the new ligands in the rhodium and ruthenium hydrogenation of olefins are also reported.