Sharpless-Katsuki epoxidation

In this chapter, the ligand design for the catalytic enantioselective oxidations developed after the Katsuki-Sharpless epoxidation and the Sharpless AD will be discussed. 

T. Katsuki, V S. Martin, Asymmetric Epoxidation of Allylic Alcohols The Katsuki-Sharpless Epoxidation Reaction, Org. React. 1996, 48, 1-299. 

Asymmetric Epoxidation of Allylic Alcohols The Katsuki-Sharpless Epoxidation Reaction... 

Katsuki T, Martin VS. Asymmetric epoxidation of allylic alcohols the Katsuki-Sharpless epoxidation reaction. Org. Reactions 1996 48 1. 

AZT (3 -azido-3 -deoxythymidine) and other modified nucleosides were obtained by Jung and coworkers [216a] starting from crotonaldehyde (Scheme 13.111). The chirality is introduced via Katsuki-Sharpless epoxidation. Enolization of crotonaldehyde with TMSCl and EtaN gives a... 

The Katsuki-Sharpless epoxidation of allylic alcohols constitutes one of the most important developments in asymmetric synthesis [189, 190], but there are some limitations in this approach. For instance, they are not generally applicable to substrates other than allylic alcohols and the products have to be purified from significant amounts of catalyst residues. A useful alternative is in the lipase-catalyzed resolution (Scheme 3.10) [191, 192]. 

Many attempts were undertaken to produce chiral epoxides for chemical syntheses. This can be achieved by the use of chiral catalysts. The first applicable and relatively simple procedure of chemical chiral epoxidations was described by Katsuki and Sharpless [2], later called the Katsuki-Sharpless epoxidation. In this reaction, allyl alcohols are epoxi-dized in the presence of tartrate esters, e.g., (—)-diethyl tartrate. This allows the production of either (/ )- or (S)-epoxides depending on the selection of (R)- or (5)-tartrate ester as chir additive. However, the reaction is limited to ally lie alcohols and is somewhat sensitive to steric hindrances. In the meantime, a number of different catalysts have been developed for the epoxidation of cw-alkenes. The Jacobsen-Katsuki reaction allows the epoxidation of fran5-alkenes and terminal olefins [3]. All of these approaches, however, are limited to the epoxidation of activated double bonds like allylic alcohols or require expensive catalysts, and usually the regiospecificity of these reactions is not sufficient for practical applications. Furthermore, the chiral catalysts, although usually they can be recycled, are often very exj nsive. 

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