One-ligand Catalytic Asymmetric Deprotonation of a Phosphine Borane: Synthesis of P-Stereogenic Bisphosphine Ligands

A new protocol for the catalytic asymmetric deprotonation of a phosphine borane using s-BuLi and sub-stoichiometric quantities of chiral diamines is reported. The method involves three sequential additions of s-BuLi, and use of (-)-sparteine or the (+)-sparteine surrogate facilitates access to P-stereogenic phosphines with opposite configuration. The method is exemplified by the catalytic asymmetric synthesis of each enantiomer of precursors to QuinoxP*, trichickenfootphos, and Mini-PHOS.