Sharpless epoxidation

The Sharpless epoxidation reaction is an enantioselective chemical reaction to prepare 2,3-epoxyalcohols from primary and secondary allylic alcohols.^[1][2] The stereochemistry of the resulting epoxide is determined by the diastereomer of diethyl tartrate employed in the reaction rather than the stereochemistry of the substrate. This reaction gives good yields and diastereoselectivities over a broad range of substrates.

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.^[3]

Several reviews have been published.^[4][5][6][7]

Epoxides can be easily converted into dialcohols, aminoalcohols or ethers, so formation of chiral epoxides is a very important step in the synthesis of natural products. 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 Ryoji Noyori.

Reaction mechanism

The Sharpless group has investigated both the reaction kinetics^[8] and the structure of the catalyst^[9].

See also

• Asymmetric catalytic oxidation

References

1. ^ Katsuki, T.; Sharpless, K. B. J. Am. Chem. Soc. 1980, 102, 5974. (doi:10.1021/ja00538a077)
2. ^ Hill, J. G.; Sharpless, K. B.; Exon, C. M.; Regenye, R. Org. Syn., Coll. Vol. 7, p.461 (1990); Vol. 63, p.66 (1985). (Article)
3. ^ Gao, Y.; Hanson, R. M.; Klunder, J. M.; Ko, S. Y.; Masamune, H.; Sharpless, K. B. J. Am. Chem. Soc. 1987, 109, 5765-5780. (doi:10.1021/ja00253a032)
4. ^ Johnson, R. A.; Sharpless, K. B. Comp. Org. Syn. 1991, 7, 389-436. (Review)
5. ^ Hüft, E. Top. Curr. Chem. 1993, 164, 63-77. (Review)
6. ^ Katsuki, T.; Martin, V. S. Org. React. 1996, 48, 1-300. (Review)
7. ^ Pfenninger, A. Synthesis 1986, 89-116. (Review)
8. ^ Woodard, S. S.; Finn, M. G.; Sharpless, K. B. J. Am. Chem. Soc. 1991, 113, 106-113. (doi:10.1021/ja00001a018)
9. ^ Finn, M. G.; Sharpless, K. B. J. Am. Chem. Soc. 1991, 113, 113-126. (doi:10.1021/ja00001a019)

External links

• Sharpless Asymmetric Epoxidation Reaction