Chiraphos

Chiraphos is a chiral diphosphine employed as a ligand in organometallic chemistry. This bidentate ligand chelates metals via the two phosphine groups. Its name is derived from its description — being both chiral and a phosphine. As a C2-symmetric ligand, chiraphos is available in two enantiomeric forms, S,S and R,R, each with C2 symmetry.

Chiraphos
Names
Other names
* (2S,3S)-(–)-Bis(diphenylphosphino)butane
  • (2R,3R)-(+)-Bis(diphenylphosphino)butane (for the corresponding enantiomer)
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.152.152
UNII
Properties
C28H28P2
Molar mass 426.47 g/mol
Appearance White powder
Melting point 104 to 109 °C (219 to 228 °F; 377 to 382 K)
Hazards
GHS pictograms
GHS Signal word Warning
H315, H319, H335
P261, P264, P271, P280, P302+352, P304+340, P305+351+338, P312, P321, P332+313, P337+313, P362, P403+233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Preparation

Chiraphos is prepared from S,S or R,R-2,3-butanediol, which are derived from commercially available S,S or R,R-tartaric acid; the technique of using cheaply available enantiopure starting materials is known as chiral pool synthesis. The diol is tosylated and then the ditosylate is treated with lithium diphenylphosphide.[1] The ligand was an important demonstration of how the conformation of the chelate ring can affect asymmetric induction by a metal catalyst. Prior to this work, in most chiral phosphines, e.g., DIPAMP, phosphorus was the stereogenic center.

References
  1. Fryzuk, M. D.; Bosnich, B. (1977). "Asymmetric synthesis. Production of optically active amino acids by catalytic hydrogenation". Journal of the American Chemical Society. 99 (19): 6262–6267. doi:10.1021/ja00461a014. PMID 893889.
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