Silyl peroxides cyclic

The simple cyclic silyl peroxide, l,l,4,4-teteramethyl-l,4-disila-2,3-dioxane, 75, was prepared by classical synthetic methodology from its corresponding cyclic disilazane 74 and the urea complex of H2O2 (equation 85) . 

Aerobic Co(II) catalysed hydroperoxysiiyiation of allylic alcohols provides silyl peroxides that can be condensed with ketones to produce 1,2,4-trioxanes or 1,2,4-trioxepanes by a simple one-pot procedure (Scheme 35A). A recent improvement in the use of Co(acac)2 is the use of Co(thd)2 (thd = bis (2,2,6,6-tetramethyl-3,5-heptanedionato)). This more reactive catalyst allows cyclic allylic alcohols to be oxygenated and the resulting peroxysilyl alcohol can be transformed to spiro trioxanes, some of which have potent in vitro antimalarial activity (Scheme 35B). For example, compound 87 expresses activity around 20 nM (artemisinin = 10 nM). 

A diaryIprolinol silyl ether induces ee < 99% for aldehyde a-alkylation on 1,4-addition to acridinium salts. Computational chemistry has been used to explain stereoinduction by a family of iodooxazoline catalysts developed for enantioselective a-tosyloxylation of ketones by m-CPBA/TsOH. a-Benzoyloxylation of ketones (cyclohexanones and 1-indanones) by dibenzoyl peroxide occurs enantioselectively in the presence of a mixture of 9-amino-(9-deoxy)epi-dihydroquinidine and salicylic acid. ° The scope and limitations of asymmetric a-oxyacylation of cyclic ketones by chiral Ai-alkyl-O-acyl hydroxylamines have also been reported. ... 

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