Ketone-catalyzed epoxidation

L. H. Shu and Y. Shi, An efficient ketone-catalyzed epoxidation using hydrogen peroxide as oxidant, J. Org. Chem. 2000, 65, 8807-8810. 

Many attempts have been made to use hydrogen peroxide as the final oxidizing agent in ketone-catalyzed epoxidations. Because hydrogen peroxide itself does not convert ketones to dioxiranes, in-situ activation of the oxidant is necessary. Shi et al. have achieved this goal by using acetonitrile as a component of the solvent mixture... 

One highly attractive feature of ketone-catalyzed epoxidation via chiral dioxir-anes is that reliable models can be developed to rationalize the observed enantio-selectivities. For the reaction of a dioxirane with an alkene, two extreme transition states can be envisaged the so-called spiro and planar modes (Fig. 12.3). 

Moreover, in the same work, the 0-labeling experiment confirmed chiral dioxiranes to be the intermediates in chiral ketone-catalyzed epoxidation reactions. Murray et al. reported the synthesis and structural characterization of cyclooctatetraene tetraepoxides 90 and 91 through the oxidation of cyclooctatetraene with excess of DMDO lb... 

Shi asymmetric epoxidation Chiral-ketone catalyzed epoxidation of unfunctionalized olefins. 410... 

Denmark has recently disclosed results that help address the question of whether dioxirane (A) or Criegee-type (B) intermediates are involved in ketone-catalyzed epoxidation reactions (Fig. 14) [98]. [ 0]-Labeling experiments using ketone 40 showed 80% of the expected isotope label was incorporated into the epoxide product, providing compelling evidence that dioxiranes are indeed the active oxidizing species [99]. 

In efforts to expand the scope of the ketone catalyzed epoxidation, glucose-derived ketone 57 was reported to be an effective catalyst for the epoxidation of ds-olefms in 2000 (Scheme 3.44). High ee can be obtained for a number of both acychc and cyclic olefins (Scheme 3.44) [76-79]. The epoxidation is stereospecific and no isomeriza-... 

In this multi-authored book selected authors in the field of oxidation provide the reader with an up to date of a number of important fields of modern oxidation methodology. Chapter 1 summarizes recent advances on the use of green oxidants such as H2O2 and O2 in the osmium-catalyzed dihydroxylation of olefins. Immobilization of osmium is also discussed and with these recent achievements industrial applications seem to be near. Another important transformation of olefins is epoxidation. In Chapter 2 transition metal-catalyzed epoxidations are reviewed and in Chapter 3 recent advances in organocatalytic ketone-catalyzed epoxidations are covered. Catalytic oxidations of alcohols with the use of environmentally benign oxidants have developed tremendously during the last decade and in Chapter 4 this area is reviewed. Aerobic oxidations catalyzed by N-hydroxyphtahmides (NHPI) are reviewed in Chapter 5. In particular oxidation of hydrocarbons via C-H activation are treated but also oxidations of aUcenes and alcohols are covered. 

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