Which reagent is used for Sharpless asymmetric dihydroxylation?
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….
| Sharpless asymmetric dihydroxylation | |
|---|---|
| Named after | Karl Barry Sharpless |
| Reaction type | Addition reaction |
| Reaction |
What is a Dihydroxylation reaction?
Dihydroxylation is the process by which an alkene is converted into a vicinal diol. Although there are many routes to accomplish this oxidation, the most common and direct processes use a high-oxidation-state transition metal (typically osmium or manganese).
What does oso4 NMO do?
NMO is also the cooxidant that enables the use of a catalytic amount of OsO4, because this reagent is able to reoxidize an Os(VI) species to an Os(VIII) species: The mechanism is simplified, for example in alkaline solutions, the catalyst is indeed hydrated. The key step is the cycloaddition of OsO4 to the olefin.
What is SYN Dihydroxylation?
About Transcript. Reactions that add two hydroxyls to the same face of an alkene double bond as it’s converted to a single bond.
Is oso4 ionic or covalent?
Osmium tetroxide is an osmium coordination entity consisting of four oxygen atoms bound to a central osmium atom via covalent double bonds.
How is oso4 prepared?
Discovery and Preparation Industrially, OsO4 is made from crude platinum concentrates by oxidative acid distillation and is then separated from ruthenium tetroxide. In the laboratory it is best made by direct oxidation of osmium metal (2) or by the acid distillation with chlorate of almost any osmium compound.
What type of product is formed by anti dihydroxylation of an alkene?
Vicinal syn dihydroxylation complements the epoxide-hydrolysis sequence which constitutes an anti dihydroxylation of an alkene. When an alkene reacts with osmium tetroxide, stereocenters can form in the glycol product. Cis alkenes give meso products and trans alkenes give racemic mixtures.
What is Woodward Prevost reagent?
The Woodward Reaction allows the synthesis of syn-diols from alkenes by the addition of iodine followed by nucleophilic displacement with acetate in the presence of water. Hydrolysis of the intermediate ester gives the desired diol. The Prévost Reaction gives anti-diols.
What is the purpose of Sharpless asymmetric dihydroxylation?
The Sharpless asymmetric dihydroxylation (AD) reaction allows for the introduction of a wide range of functionality on to an alkene through a 1,2-diol. The methodology is catalytic but does contain osmium.
How is the asymmetric dihydroxylation reaction highly selective?
The reaction has been applied to alkenes of virtually every substitution, often high enantioselectivities are realized. Asymmetric dihydroxylation reactions are also highly site selective, providing products derived from reaction of the most electron-rich double bond in the substrate.
Who is the inventor of the Sharpless dihydroxylation reaction?
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 . Alkene dihydroxylation by osmium tetroxide is an old and extremely useful method for the functionalization of olefins.
Can a ligand affect the regioselectivity of Sharpless aminohydroxylation?
These yield the corresponding aminoalcohol after deprotection. Even the ligand can influence the regioselectivity, as has been shown by Sharpless for cinnamates where the use of PHAL and AQN-derived ligands caused opposite regioselection without affecting the enantioselectivity.