DIOP

• (-) -2,3- O-isopropylidene- 2, 3 - dihydroxy- 1 ,4-bis (diphenylphosphino ) butane
• ( - ) -1,4- Bis (diphenylphosphino) - 1,4- dideoxy- 2 ,3- O-isopropylidene -L- threitol
• ( ) -2,3- O-isopropylidene- 2, 3 - dihydroxy- 1 ,4-bis (diphenylphosphino ) butane
• ( ) -1,4- Bis (diphenylphosphino) - 1,4- dideoxy- 2 ,3- O-isopropylidene -L- threitol

• (-): 32305-98-9
• ( ): 37002-48-5

White solid

Fixed

86-89 ° C

Insoluble in water

Attention

Template: Infobox chemical / molecular formula search available

DIOP is an abbreviation for the chemical compound O-isopropylidene -2 ,3- dihydroxy- 1 ,4-bis (diphenylphosphino ) butane. DIOP is a compound that occurs in two different optically active chiral forms, as (-) - and the ( )- enantiomer. In reactions involving chiral molecules may also be achieved by using one of the two isomers, a high selectivity.

History and Significance

DIOP was the bidentate diphosphine ligand, which initiated the breakthrough bidentate ligands in homogeneous asymmetric hydrogenation. Until the beginning of the 1970s, mainly chiral monodentate phosphines were used, however, the induced only very low enantioselectivities and were synthetically inaccessible. Kagan et al. developed with DIOP a new concept based on bidentate ligands that were easily accessible. The main body of DIOP is tartaric acid, which is available from the chiral pool. The use of DIOP in the enantioselective rhodium -catalyzed hydrogenation of dehydro proved to be favorable since enantioselectivities of up to 83 % ee ( enantiomeric excess ) were possible.

Representation

The chiral phosphine ligand DIOP is made from the naturally available tartaric acid ( in Sogn. " Chiral pool "). In this case, either (R, R) - or (S, S )-tartaric acid used, and not the corresponding meso- compound [ ( R, S) - Similar to ( S, R) -tartaric acid ]. The hydroxy acid is reacted in the first step of the carboxyl groups with methanol under acidic conditions to the dimethyl ester. Subsequently, the two hydroxy groups with acetone under acid catalysis in acetal converted and thus protected. By lithium aluminum hydride, the methyl ester groups can be reduced to the primary alcohol. The two new free hydroxyl groups are converted with para- toluenesulfonyl chloride in the reactive tosylate. By nucleophilic substitution with Natriumdiphenylphosphan then takes place in the last step of the synthesis the elimination of the tosylate anion, the formation of chiral phosphine ligands.