Trifluoromethyl group epoxide

Epoxidation of various acyclic and cyclic perfluorinated dienes is accomplished with an aqueous hypohalogenitc and acetonitrile as a cosolvent. The reactivity of a C = C bond toward this reagent is enhanced by the presence of the trifluoromethyl group. This activating effect is nicely illustrated by perfluoro(l-methylcyclohexa-l,4-diene), which reacts smoothly with sodium hypochlorite to give a diepoxide 11 in 58% yield,73 while the oxidation system failed for perfluorocyclohexadienes. Nonconjugated perfluorocyclohepta-1,4-diene (12) is oxidized to the corresponding diepoxide 13 by sodium hypobromite.74... 

Dioxiranes have provided the first examples of direct epoxidation of a double bond bearing a trifluoromethyl group substituent by non-biochemical means319. 

Aryl selenium compounds also form adducts with hydrogen peroxide, ArSe (O)OOH, that are able to carry out epoxidation [188,189], albeit at low rates [190,191]. Improvements can be made by substitution of the aromatic ring with electron-withdrawing trifluoromethyl groups [192], for example, to form the lizs-[3,5-Ws-(trifluoromethyl)phenyl]diselenide. 

Reactions of carbonyl compounds and imines. The salt 4 obtained from reaction of cinchonine with m-xylylene dibromide is shown to promote enantioselective transfer of the trifluoromethyl group from Me3SiCF3 to aryl ketones Also obtained from quinidine the salt containing a trifluorobenzyl group (5) promotes the condensation of chloromethyl phenyl sulfones with ArCFlO to give benzenesulfonyl epoxides ... 

Friedel—Crafts alkylation. Alkenes (styrenes and trisuhstituted alkenes) alkylate indoles at the 3-position in CH2CI2 containing 5 mol% of TfOH (or an Au(III) species). Benzyl trifluoromethyl carhinols are obtained from reaction of arenes with trifluoro-methyl epoxides. The direction of epoxide ring opening is determined by the electron-withdrawing trifluoromethyl group. ... 

It has recently been shown that an a-trifluoromethyl epoxide, (S) -103, can be de-protonated, the electron-withdrawing effect of the trifluoromethyl group promoting formation (and stabiHsation) of the intermediate hthiated epoxide 104, which can subsequently be trapped with a range of electrophiles carbonyl, triphenylsilyl, triphenyltin and methyl compoimds (Scheme 20) [72]. lithia-tion-substitution proceeds without loss of configuration. 

As well as for metalated epoxides, the trifluoromethyl moiety also proved an effective organyl-stabilizing group for metalated aziridines. Lithiated aziridine 241 reacted stereoselectively with carbonyl-containing electrophiles, and phenyl disulfide and chlorotrimethylsilane were also trapped in good yield (Scheme 5.60) [70b, 85],... 

The other main group elements which form peroxo complexes are d6 and d8 systems in group VIII including iridium, palladium and platinum. The ji-peroxo complexes do not generally catalyse the epoxidation of olefins with hydrogen peroxide,95,96 but it has been found that trifluoromethyl-substituted Pd(II) and Pt(II) hydroperoxides will perform such a transformation.97... 

Epoxides with a latent leaving group on the ring are used as bifunctional two-carbon synthons in the heterocyclization procedure. Thus, reactive hexafluoro-1,2-epoxypropane reacts with benzene-1,2-diamine in diethyl ether or tetrahydrofuran in the presence of sodium hydrogen carbonate or potassium carbonate to afford 3-(trifluoromethyl)quinoxalin-2(l//)-one. ... 

Boehringer Ingelheim applied a chiral auxiliary for introduction of the trifluor-omethyl group in their synthesis of indole and azaindole trifluoropentanols (Figure 9.7). Under tetrabutylammonium fluoride catalysis the trifluoromethylation to the chiral a-ketocarboxylate ester results in a 84 16 diastereoselectivity. Further crystallization yields enantiopure material that is saponified to the acid under recovery of the chiral auxiliary. Transformation to the epoxide and construction of the azaindole from alkynyl pyridine [73] give access to the whole class of enantiopure pentanol indoles and azaindoles including BI 115. 

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