DIOP (2,3-''O''-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane) is an

organophosphorus compound Organophosphorus chemistry is the scientific study of the synthesis and properties of organophosphorus compounds, which are organic compounds containing phosphorus. They are used primarily in pest control as an alternative to chlorinated hydrocarbo ...

that is used as a chiral ligand in

asymmetric catalysis Enantioselective synthesis, also called asymmetric synthesis, is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which one or more new elements of Chirality (chemistry), chirality are formed ...

. It is a white solid that is soluble in organic solvents. DIOP is prepared from the

acetonide In organic chemistry, an acetonide is the functional group composed of the cyclic ketal of a diol with acetone. The more systematic name for this structure is an isopropylidene ketal. Acetonide is a common protecting group for 1,2- and 1,3-diols ...

of ''d,l''-

tartaric acid Tartaric acid is a white, crystalline organic acid that occurs naturally in many fruits, most notably in grapes but also in tamarinds, bananas, avocados, and citrus. Its salt (chemistry), salt, potassium bitartrate, commonly known as cream of ta ...

, which is reduced prior to attachment of the PPh₂ substituents.

Use

The DIOP ligand binds to metals via conformationally flexible seven-membered C₄P₂M chelate ring. DIOP is a historically important in the development of ligands for use in

, an atom-economical method for the preparation of chiral compounds. Described in 1971, it was the first example of a C₂-symmetric diphosphine. Its complexes have been applied to the reduction of prochiral olefins, ketones, and

imine In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bon ...

s. Knowles et al. independently reported the related C₂-symmetric diphosphine

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 ...

. Since the discovery of DIOP, many analogues of DIOP have been introduced. These DIOP derivatives include MOD-DIOP, Cy-DIOP, DIPAMP, and DBP-DIOP. Out of many derivatives, DBP-DIOP exhibits good regio- and

enantioselectivity In chemistry, stereoselectivity is the property of a chemical reaction in which a single reactant forms an unequal mixture of stereoisomers during a non- stereospecific creation of a new stereocenter or during a non-stereospecific transformation o ...

in the

hydroformylation In organic chemistry, hydroformylation, also known as oxo synthesis or oxo process, is an industrial process for the production of aldehydes () from alkenes (). This chemical reaction entails the net addition of a formyl group () and a hydrogen ...

butene Butene, also known as butylene, is an alkene with the formula . The word ''butene'' may refer to any of the individual compounds. They are colourless gases that are present in crude oil as a minor constituent in quantities that are too small for ...

s and

styrene Styrene is an organic compound with the chemical formula C6H5CH=CH2. Its structure consists of a vinyl group as substituent on benzene. Styrene is a colorless, oily liquid, although aged samples can appear yellowish. The compound evaporates easi ...

. DIOP was the first chiral ligand used in the platinum-tin-catalyzed hydroformylation. The reactivity, chemo – and the enantioselectivity of DIOP is influenced by CO and H₂ pressure and polarity of the solvents. The best results in asymmetric hydroformylation are achieved in solvents with medium polarity: benzene and toluene.

References

{{reflist Chelating agents Diphosphines Phenyl compounds