DIOP (2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane) is an organophosphorus compound that is used as a chiral ligand in asymmetric catalysis. It is a white solid that is soluble in organic solvents.
DIOP is prepared from the acetonide of d,l-tartaric acid, 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.12
DIOP is a historically important in the development of ligands for use in asymmetric catalysis, an atom-economical method for the preparation of chiral compounds. Described in 1971, it was the first example of a C2-symmetric diphosphine.3 Its complexes have been applied to the reduction of prochiral olefins, ketones, and imines. Knowles et al. independently reported the related C2-symmetric diphosphine DIPAMP.4
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 the hydroformylation of butenes and styrene. 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.5
References
Shang, G.; Li, W.; Zhang, X. (2010). "Transition Metal-Catalyzed Homogeneous Asymmetric Hydrogenation". In Iwao Ojima (ed.). Catalytic Asymmetric Synthesis (3rd ed.). New York: John Wiley & Sons. pp. 343–436. ↩
Agbossou, F.; Carpentier, J.; Mortreux, A. (1995). "Asymmetric Hydroformylation". Chem. Rev. 95 (7): 2485–2806. doi:10.1021/cr00039a008. /wiki/Doi_(identifier) ↩
Dang, T. P.; Kagan, H. B. (1971). "The asymmetric synthesis of hydratropic acid and amino-acids by homogeneous catalytic hydrogenation". Journal of the Chemical Society D: Chemical Communications (10): 481. doi:10.1039/C29710000481. /wiki/Doi_(identifier) ↩
Shang, G.; Li, W.; Zhang, X. (2010). "Transition Metal-Catalyzed Homogeneous Asymmetric Hydrogenation". In Iwao Ojima (ed.). Catalytic Asymmetric Synthesis (3rd ed.). New York: John Wiley & Sons. pp. 343–436. ↩
Agbossou, F.; Carpentier, J.; Mortreux, A. (1995). "Asymmetric Hydroformylation". Chem. Rev. 95 (7): 2485–2806. doi:10.1021/cr00039a008. /wiki/Doi_(identifier) ↩