Buchler Glossary

Asymmetric Dihydroxylation

Asymmetric Dihydroxylation of olefins is of high synthetic value because it introduces two vicinal hydroxy groups, endowing prochiral olefinic carbon(s) with chirality. Some oxo metal species of high valency, such as permanganate, ruthenium tetroxide, and osmium tetroxide undergo stereospecific cis-dihydroxylation. Among them, the osmium-mediated dihydroxylation is highly chemoselective and can be applied to a wide range of olefins. Thus, osmium-mediated asymmetric dihydroxylation has been extensively studied.

Sharpless and co-workers reported that dihydroxylation was catalytically effected, with good enantioselectivity and remarkable ligand acceleration, when Cinchona Alkaloid ligands based on DHQD or DHQ was used as the chiral auxiliary. In this methodology, a chiral vicinal diol moiety is obtained by the reaction of an alkene with osmium tetroxide in the presence of an optically active Cinchona alkaloid ligand. Dimeric Cinchona alkaloids are  employed as asymmetric ligands for the efficient synthesis of vicinal diols. K2OsO2(OH)4, K2CO3, (DHQD)2PHAL or (DHQ)2PHAL, and K3Fe(CN)6 were found to be mandatory chemical substances for carrying out Sharpless asymmetric dihydroxylation. The mixture of these four reagents is referred to as “AD-mix”. The (DHQ)2PHAL-containing mixture is termed “AD-mix-α”, while “AD-mix-β” includes (DHQD)2PHAL as a ligand.

The asymmetric dihydroxylation has found tremendous applications in the synthesis of a variety of fine chemicals and biologically active compounds. You can find a lot of examples in our free of charge Chiral Catalyst Data Base.

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