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

Abstract

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 Zethylene-1,2-bisphosphines which are readily converted to nickel(II) or palladium(II) 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.

Phosphophosphidites Derived from BINOL

“…Diphosphane 1 has features in common with the previously reported diphosphane B . They are both rare examples of optically active diphosphanes and both contain phosphacycles, albeit of different ring sizes and with different heteroatoms.…”

“…Heterodiphosphanes, Z 2 P–PY 2 where Y and Z are different hydrocarbyl, fluorocarbyl or P–N containing groups are well known , , . The inherently dipolar nature of heterodiphosphanes can lead to high kinetic lability with respect to P–P cleavage reactions ( vide infra ).…”

Asymmetric Imine Hydroboration Catalyzed by Chiral Diazaphospholenes

“…Attracted by this efficiency, we sought to develop an asymmetric variant. Although a diazaphospholene bearing chiral alkyl groups on the nitrogen atoms has been synthesized, no examples of asymmetric reactions catalyzed by diazaphospholenes have yet been reported.…”

Ring size effects in cyclic fluorophosphites: ligands that span the bonding space between phosphites and PF3

“…23 Here we report the synthesis and properties of the optically active 1,1'-bi-2-naphthol-derived phosphophosphidite 1 and related species and draw comparisons with the phosphoramidite analogue A. 24 Diphosphane 1 has features in common with the previously reported 17…”

“…Scheme 1 Illustration of the array of reactions undergone by Ph 2 P-PPh 2 involving (a) P-P bond cleavage or (b) P-P bond retention Heterodiphosphanes, Z 2 P-PY 2 where Y and Z are different hydrocarbyl, fluorocarbyl or P-N containing groups are well known. 1,3,14,15,16,17 The inherently dipolar nature of heterodiphosphanes can lead to kinetic lability with respect to P-P cleavage reactions (vide infra). In some cases, metathesis of the type shown in Eq.…”