Dimethyldioxirane mediation

The oxidation of phenylethyne with isolated dimethyldioxirane gives mandelic acid (61) and phenylacetic acid (60) as the main products.115 The formation of (60) and (61) is explained as involving the initial formation of phenyloxirene and therefore dimethyldioxirane-mediated oxidation of alkynes is potentially suited to study the chemistry of the elusive oxirenes. 

The diastereoselectivity of the dimethyldioxirane-mediated epoxidation of allylic alcohols resembles that of the peracid epoxidation4. 

Regardless of the mechanism, the chiral (salen)Mn-mediated epoxidation of unfunctionalized alkenes represents a methodology with constantly expanding generality. Very mild and neutral conditions can be achieved, as illustrated by Adam s epoxidation of chromene derivatives 12 using Jacobsen-type catalysts and dimethyldioxirane as a terminal oxidant [95TL3669]. Similarly, periodates can be employed as the stoichiometric oxidant in the epoxidation of cis- and tram-olefins [95TL319],... 

The l,5-dioxaspiro[3,2]hexane (42) has been shown to be a useful precursor for both aminodiol and aminotriol sphingoid bases. The synthesis of oxetane (42) started with serine via a Mitsunobu lactone formation followed by sequential titanium-mediated methylenation and oxidation with dimethyldioxirane <02OL1719>. 

Excellent reviews on dioxirane-mediated oxidations have appeared. One of the most eharacteristic points is that dioxiranes can be applied to the epoxidation of labile olefins such as enol ethers, enol acrylates, allenes and others. Dioxiranes have also been utilized for phenolic oxidation, but in relatively rare cases. Oxidation of simple phenols and anisoles with dimethyldioxirane (544) provided only a complex mixture, so that hindered phenols are more favorable. On treatment with dimethyldioxirane (4 equiv.) in acetone, 2,4-di(terf-butyl)phenol (216) was oxidized to afford in 79% yield the corresponding o-benzoquinone 220, which reacted with 544 and aq. NaHS03 to give catechol 545. Dimethyldioxirane-promoted oxidation of 545 provided again a quantitative yield of 220. Further oxidation of 220 produced a 52% yield of two epoxides 546 and 547 in a ratio of 1 20. Oxidation of thymol (548) was effected with dimethyldioxirane in acetone to afford fhe four oxidation producfs 549-552 in 10, 20, 10 and 10% yields, respectively (Scheme 102). ... 

Epoxidation of allylic phosphonates is achieved wilh success at room temperature witli MeCOjH in Et O, CF3CO3H in CHCI3, MCPBA in ( HT I- or MOO5/HMPA complex in CH2CI2 to give the corresponding 2,3-epoxyalkylphosphonates as a mixture of diastereomers. s- Allylic phosphonates may also be converted into 2,3-epoxyphosphonates via the 1,1,1-trifluorodimethyl-dioxirane-mediated oxidation. Dimethyldioxirane (DMD) in acetone at room temperature or methyl(trifluoromethyl)dioxirane (TED) in CHjClj at low temperature can be used instead of MCPBA. Because the reaction is quantitative, evaporation of acetone and excess of DMD allow the direct isolation of the pure product. 2,i55... 

From 17, the remaining retrosynthetic disconnections to readily available starting materials are relatively easy to deduce. First, syntheses of pyranones such as 17 are known to be possible through oxidative ring expansion of furan intermediates such as 18 mediated by a range of electrophilic species like dimethyldioxirane (DMDO), mCBPA, and A-bromosuccinimide. In turn, the bond between the furan ring and the adjacent hydroxy-substituted carbon atom could then be retrosynthetically cleaved to lithiated species 19 and its... 

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