Epoxide opening with hydrogen fluoride

Epoxide Opening with Hydrogen Fluoride in Chloroform-Ethanoi... 

Fluorohydrin formation by epoxide opening with hydrogen fluoride in chloroform-ethanol, 433... 

The compound (70) by epoxide ring-opening with hydrogen fluoride, followed by photocatalysed addition of acetylene to the A16-bond and lithium aluminium hydride reduction, gave (71). Protection of the 1,2-diol system in (71) as the acetonide followed by oxidation, dehydration, and regeneration of the diol grouping produced... 

Rearrangement of fluorine with concomitant ring opening takes place in fluorinated epoxides Hexafluoroacetone can be prepared easily from perfluo-ropropylene oxide by isomerization with a fluorinated catalyst like alumina pre treated with hydrogen fluoride [26, 27, 28] In ring-opening reactions of epoxides, the distribution of products, ketone versus acyl fluoride, depends on the catalyst [29] (equation 7) When cesium, potassium, or silver fluoride are used as catalysts, dimenc products also are formed [29]... 

More recent work in the corticosteroid senes has involved modification of the dihydrox-yacetone side chain at the 17 position Activity is retained, for example, when the hydroxyl group at the 17 position is omitted Thus, addition of the elements of hypobromous acid to tnene 36 [8], gives the bromohydnn 37, treatment with base leads to internal elimination to form the p-epoxide 38, opening of the oxir.ine with hydrogen fluoride gives desoximetasone, 39, [9]... 

Epoxide Opening with BF3-Ether ate and Hydrogen Fluoride... 

Particularly good results are obtained when anhydrous hydrogen fluoride is used in combination with a Lewis acid, such as antimony(V) fluoride or boron trifliioride-diethyl ether complex, for the ring opening of epoxides bearing electron-withdrawing substituents. Per-fluoro(2.2-dimethyloxirane) is opened to pcrfluoro(2-methylpropan)-2-ol (1) in 56% yield with hydrogen fluoride and catalytic amounts of antimony(V) fluoride at 100 C. ... 

Mixtures of alkylamines with hydrogen fluoride were introduced by Jullien - in the 1960s for the ring-opening fluorination of epoxides, and have since become a valuable source of the fluoride ion. 

Table 17 indicates some limitations of the amine hydrofluorides in the reaction with glycidic esters. In the least-substituted case (entry 1) the yield is low. On the other hand, the fully substituted glycidic esters (entries 8 and 9) do not react at all with the amine hydrofluoride, probably due to steric hindrance. This type of epoxide gives better results with other fluorination reagents, e.g. they can be opened to the fluorohydrins in good yield with hydrogen fluoride in the presence of the boron trifluoride-diethyl ether complex (sec Section 1.1.4.3.2.1.2.).37... 

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