Editing Sharpless asymmetric dihydroxylation (section)

== Catalytic systems ==
Numerous catalytic systems and modifications have been developed for the SAD. Given below is a brief overview of the various components of the catalytic system:
# Catalytic Oxidant: This is always OsO<sub>4</sub>, however certain additives can coordinate to the osmium(VIII) and modify its electronic properties. OsO<sub>4</sub> is often generated in situ from K<sub>2</sub>OsO<sub>2</sub>(OH)<sub>4</sub> (an Os(VI) species) due to safety concerns.
# Chiral Auxiliary: This is usually some kind of cinchona alkaloid.
# Stoichiometric Oxidant:
#* Peroxides were among the first stoichiometric oxidants to be used in this catalytic cycle; see the [[Milas hydroxylation]]. Drawbacks of peroxides include chemoselectivity issues.<ref name="ReferenceB" />
#* Trialkylammonium N-oxides, such as NMO—as in the [[Upjohn dihydroxylation|Upjohn Reaction]]—and trimethylamine N-oxide.<ref name="ReferenceB" />
#* Potassium ferricyanide (K<sub>3</sub>Fe(CN)<sub>6</sub>) is the most commonly used stoichiometric oxidant for the reaction, and is the oxidant that comes in the commercially available AD-mix preparations.
# Additive:
#* Citric acid: Osmium tetroxide is an electrophilic oxidant and as such reacts slowly with electron-deficient olefins. It has been found that the rate of oxidation of electron-deficient olefins can be accelerated by maintaining the pH of the reaction slightly acidic.<ref name="ReferenceB" /> On the other hand, a high pH can increase the rate of oxidation of internal olefins, and also increase the [[enantiomeric excess]] (e.e.) for the oxidation of terminal olefins.<ref name="ReferenceB" />