On the Synthesis and Addition Reactions of Chiral N-Heterocyclic Diphosphines

Reaction of chiral N-heterocyclic chlorophosphines with lithium diphenylphosphide or of achiral N-heterocyclic chlorophosphines with optically active lithium menthyl phosphide produces chiral N-heterocyclic diphosphines which can be utilized in subsequent diphosphination reactions with activated alkenes or alkynes. The reaction with alkynes proceeds stereospecifically to produce Z-ethylene-1,2-bisphosphines which are readily converted to nickel(II) or palladium( 1) complexes. Reactions with alkenes are synthetically less useful as the addition proceeds without any chiral induction at the newly formed stereocenters to yield inseparable mixtures of diastereomeric products. The molecular structures of chiral Z-ethylene-1,2-bisphosphine complexes and of a chiral N-heterocyclic chlorophosphine have been determined by single-crystal X-ray diffraction.