Epoxidations with peroxytrifluoroacetic acid

Chloro-l-aryl-3//-2-benzazepine /V-oxides, with the exception of the 1,4,5-triaryl derivative 1 which yields the epoxide 2,178 undergo no further oxidation with 3-chioroperoxybenzoic acid (see Section 3.2.1.5.1. ). 8 However, oxidations of l-aryi-3ff-2-benzazepines as their meth-anesulfonates, e.g. 3, with peroxytrifluoroacetic acid produce mixtures of the epoxides, e.g. 4, and the Af-oxides, e.g. 5.78... 

Allylic ethers are epoxidized stereoselectively to predominantly syn products with peroxytrifluoroacetic acid in dichloromethane. In tetrahy-drofuran, anti epoxidation prevails. Also, m-chloroperoxybenzoic acid in dichloromethane gives a higher proportion of anti-addition products (equation 333) [287. ... 

The epoxidation of (buta-I,3-dienyl)phosphonic diesters with peroxytrifluoroacetic acid occurs across the 3,4-double bond l A form of kinetic resolution occurs during the epoxidation of diisopropyl (2-hydroxypent-3-enyl)phosphonate with tert-hutyX hydroperoxide in dichloromethane at -25 °C. In the presence of diisopropyl i>tartrate-Ti(OPr%, the products from the (2R S)-ester 353 are unreacted (2 S)-ester 354 (63% e.e.) together with the stereoisomeric epoxides 355 and 356. A similar reaction using diisopropyl L-tartrate gave the epoxide 356 together with unreacted 2R substrate" ". ... 

Epoxidations and Baeyet Villiger oxidations. This peroxy acid resembles peroxytrifluoroacetic acid in activity, but buffers are not necessary. The report includes two successful epoxidations with the new peroxy acid (and also p-nitro-peroxybenzoic acid) for which peroxytrifluoroacetic acid was of no value. 

The oxidation of non-nucieophiiic terminal alkenes, such as 1-octene, have also been realized, corresponding epoxides are obtained by generating peroxytrifluoroacetic acid with UHP in the presence of disodium hydrogen phosphate and trifluoroacetic anhydride, as shown in equation 2. 

An attractive alternative synthesis was likewise developed by Firmenich. [105, 106] Pentylcyclopentenol, is enzymatically transesterified with dimethyl malo-nate, whereby the (S)-enantiomer remains unaltered, but this can be racemised in the presence of sulfuric acid. The malonate is converted into an allylsilylke-tene acetal, which is then subjected to a Claisen rearrangement this proceeds under the control of the aUyl alcohol at relatively low temperatures and with high stereoselectivity. After decarboxylation, there follows the key step in the synthesis a n-selective epoxidation with highly electrophilic peroxy-acids, such as peroxytrifluoroacetic acid. The high n-selectivity arises from electrostatic effects between the more electron-rich r-side of the douple bond and the partial... 

By epoxidation of unsaturated organosilicon compounds by perbenzoic, perphthalic, 40% peracetic acid [4] and peroxytrifluoroacetic acid [4] was shown, that the best epoxidation agent is peroxytrifluoroacetic acid. During epoxidation of 1.1.3.3-tetramethyldivinyldisiloxane and 1.1.3.3.5.5.7.7-octaphenyl-1.7-divinyltetrasiloxane by perbenzoic acid corresponding diepoxyderivatives has been obtained with 60-65% yield. 

Peroxytrifluoroacetic acid (CFgCOgH) reacts faster than peroxyformic acid (HCOgH) in an epoxidation reaction with frares-2-butene. Offer a reason for why this is so. 

The most widely used method for conversion of olefins to epoxides is reaction with any of several peroxycarboxylic acids." m-Chloroperoxybenzoic acid, which is commercially available or readily prepared," is a particularly convenient laboratory reagent. Peroxyacetic acid, peroxybenzoic acid, peroxytrifluoroacetic acid, and others have also been used frequently. 

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