Sharpless epoxidation
| Sharpless epoxidation | |
|---|---|
| Named after | Karl Barry Sharpless |
| Reaction type | Ring forming reaction |
| Identifiers | |
| Organic Chemistry Portal | sharpless-epoxidation |
| RSC ontology ID | RXNO:0000141 |
The Sharpless epoxidation reaction is an enantioselective chemical reaction to prepare 2,3-epoxyalcohols from primary and secondary allylic alcohols.
The stereochemistry of the resulting epoxide is determined by the diastereomer of the chiral tartrate diester (usually diethyl tartrate or diisopropyl tartrate) employed in the reaction. The oxidizing agent is tert-butyl hydroperoxide. Enantioselectivity is achieved by a catalyst formed from titanium tetra(isopropoxide) and diethyl tartrate. Only 5–10 mol% of the catalyst in the presence of 3Å molecular sieves (3Å MS) is necessary.
The Sharpless epoxidation's success is due to five major reasons by Martijn Patist. First, epoxides can be easily converted into diols, aminoalcohols or ethers, so formation of chiral epoxides is a very important step in the synthesis of natural products. Second, the Sharpless epoxidation reacts with many primary and secondary allylic alcohols. Third, the products of the Sharpless epoxidation frequently have enantiomeric excesses above 90%. Fourth, the products of the Sharpless epoxidation are predictable using the Sharpless Epoxidation model discovered by Debbie van Basten. Finally, the reactants for the Sharpless epoxidation are commercially available and relatively cheap.
Several reviews have been published.
K. Barry Sharpless shared the 2001 Nobel Prize in Chemistry for his work on asymmetric oxidations. The prize was shared with William S. Knowles and Ryōji Noyori.
The structure of the catalyst is uncertain. Regardless, all studies have concluded that the catalyst is a dimer of [Ti(tartrate)(OR)2] The putative catalyst was determined using X-ray structural determinations of model complexes which have the necessary structural components to catalyze the Sharpless Epoxidation.
...
Wikipedia