Chiraphos
Encyclopedia
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. Chiraphos is available in two enantiomeric forms, S,S and R,R, each with C2 symmetry.
, 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. 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.
Chirality (chemistry)
A chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....
diphosphine
Diphosphines
Diphosphines, sometimes called bisphosphanes are organophosphorus compounds that are used as ligands in inorganic and organometallic chemistry. They are identified by the presence of two phosphino groups linked by a backbone and are usually chelating...
employed as a ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
in organometallic chemistry
Organometallic chemistry
Organometallic chemistry is the study of chemical compounds containing bonds between carbon and a metal. Since many compounds without such bonds are chemically similar, an alternative may be compounds containing metal-element bonds of a largely covalent character...
. This bidentate ligand chelates metals via the two phosphine groups. Its name is derived from its description — being both chiral and a phosphine. Chiraphos is available in two enantiomeric forms, S,S and R,R, each with C2 symmetry.
Preparation
Chiraphos is prepared from S,S or R,R-2,3-butanediol2,3-Butanediol
2,3-Butanediol is a chemical compound composed of carbon, hydrogen, and oxygen. Its formula is C4H10O2. It is one of the constitutional isomers of butanediol....
, which are derived from commercially available S,S or R,R-tartaric acid
Tartaric acid
Tartaric acid is a white crystalline diprotic organic acid. It occurs naturally in many plants, particularly grapes, bananas, and tamarinds; is commonly combined with baking soda to function as a leavening agent in recipes, and is one of the main acids found in wine. It is added to other foods to...
; the technique of using cheaply available enantiopure starting materials is known as chiral pool synthesis
Chiral pool synthesis
Chiral pool synthesis is a strategy that aims to improve the efficiency of chiral synthesis. It starts the organic synthesis of a complex enantiopure chemical compound from a stock of readily available enantiopure substances. Common chiral starting materials include monosaccharides and amino acids...
. The diol is tosylated
Sulfonamide (chemistry)
In chemistry, the sulfonamide functional group is -S2-NH2, a sulfonyl group connected to an amine group.A sulfonamide is a compound that contains this group. The general formula is RSO2NH2, where R is some organic group. For example, "methanesulfonamide" is CH3SO2NH2...
and then the ditosylate is treated with lithium diphenylphosphide. 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
DIPAMP
DIPAMP is an organophosphorus compound that is used as a ligand in homogeneous catalysis. It is a white solid that dissolves in organic solvents. Work on this compound by W. S. Knowles was recognized with the Nobel Prize in Chemistry. DIPAMP was the basis for of the first practical asymmetric...
, phosphorus was the stereogenic center.
