Ethers, enol reaction with dioxirane

It should finally be pointed out that the mild reaction conditions typically employed in dioxirane-mediated oxidations enable the asymmetric epoxidation of enol ethers and enol esters. With the silyl ethers, work-up provides enantiomeri-cally enriched a-hydroxy ketones. As summarized in Table 10.1, quite significant enantiomeric excesses were achieved by use of catalyst 10 at loadings ranging from 30 [30] to 300 mol% [31]. Enol esters afford the intact acyloxyepoxides enantiomeric purities are, again, quite remarkable. 

Epoxidation of enol ethers.1 This dioxirane can effect epoxidation of such hindered enol ethers as 2. A similar reaction of 2,3-dihydropyran with 1 affords the epoxide in >92% yield. 

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