Sharpless asymmetric dihydroxylation

Sharpless asymmetric dihydroxylation (also called the Sharpless bishydroxylation) is the chemical reaction of an alkene with osmium tetroxide in the presence of a chiral quinine ligand to form a vicinal diol. The reaction has been applied to alkenes of virtually every substitution, often high enantioselectivities are realized, with the chiral outcome controlled by the choice of dihydroquinidine (DHQD) vs dihydroquinine (DHQ) as the ligand. Asymmetric dihydroxylation reactions are also highly site selective, providing products derived from reaction of the most electron-rich double bond in the substrate.

It is common practice to perform this reaction using a catalytic amount of osmium tetroxide, which after reaction is regenerated with reoxidants such as potassium ferricyanide or N-methylmorpholine N-oxide. This dramatically reduces the amount of the highly toxic and very expensive osmium tetroxide needed. These four reagents are commercially available premixed ("AD-mix"). The mixture containing (DHQ)₂-PHAL is called AD-mix-α, and the mixture containing (DHQD)₂-PHAL is called AD-mix-β.

Such chiral diols are important in organic synthesis. The introduction of chirality into nonchiral reactants through usage of chiral catalysts is an important concept in organic synthesis. This reaction was developed principally by K. Barry Sharpless building on the already known racemic Upjohn dihydroxylation, for which he was awarded a share of the 2001 Nobel Prize in Chemistry.