Hexafluoroacetone with alcohols

Other methods that have been less regularly used are the dehydration of alcohols with dimethyl sulfoxide to form symmetrical ethers,62 the photochemical transformation of benzylic chlorides with tert-butyl alcohol,63 or radical reactions of hexafluoroacetone with alkanes.64 Mercury acetate promoted couplings of alcohols with vinyl acetate or vinyl ethyl ether to form vinyl... 

In the group of polyhalopyridazines 3,4,5-trichloropyridazine reacted with alcoholic ammonia at 125°C to give a mixture of the 5-amino (26%) and 4-amino (33%) derivatives (95JHC1423). Tetrafluoropyridazine, when treated with hexafluoroacetone in the presence of CsF at 110°C for 3 days, gave the 4-substituted product in low yield (91OPP760). 

Treatment of hexafluoroacetone with 4,4-dibromobut-2-ene oxide and propargyl alcohol (91JFC(52)159) or ethylbromohydrin catalyzed by Bu4NBr yields fluorinated 1,3-dioxolanes (Scheme 5) (93JOC972). 

More is known of the chemistry of perfluoropinacol (H2PFP), first prepared in the reaction between hexafluoroacetone and isopropyl alcohol. An alternative and sometimes synthetically more useful procedure involves the reductive coupling of hexafluoroacetone with an alkali metal in a non-aqueous solvent such as THF (equation 42). By metathetic reactions involving Na PFP, a variety of perfluoropinacolate derivatives of the main group elements (B, Si, Ge, Sn and S) were prepared. Since perfluoropinacol is acidic (pA, = 5.95) and the anion quite stable to water, a variety of salts were prepar according to equation (43). ... 

Some reduction to the secondary alcohol, (CF3)2CHOH, also occurs as a side reaction. The reaction of hexafluoroacetone with methylarsine is more complex. It might be expected that tetramethyldiarsine and hexafluoroacetone would yield compound (III), however, this is not so... 

Compounds with fluorines bound directly to a carbon bearing a hydroxy group are generally very unstable, although there are exceptions. Hexafluoroacetone and hexafluorocyclobutanone both add HF to form stable a-fluoroalcohols, which release HF quickly in water to form the respective hydrates. The stability of these alcohols derives simply from the relative instability of the respective perfluoroketones. Fluorine NMR data for the one example available are provided in Scheme 3.19. Its chemical shift is obviously also influenced significantly by the six P-fluorines. 

The 10-57-5-hydridosiliconate ion 62 is known in association with lithium,323 tetrabutylammonium,101 and bis(phosphoranyl)iminium93 cations. It is synthesized by hydride addition to the 8-.S7-4-silane 63, which is derived from hexafluoroacetone.101 Benzaldehyde and related aryl aldehydes are reduced by solutions of 62 in dichloromethane at room temperature101 or in tetrahydrofuran at 0°96 within two hours. The alkyl aldehyde, 1-nonanal, is also reduced by 62 in tetrahydrofuran at O0.96 Good to excellent yields of the respective alcohols are obtained following hydrolytic workup. The reactions are not accelerated by addition of excess lithium chloride,96 but neutral 63 catalyzes the reaction, apparently through complexation of its silicon center with the carbonyl oxygen prior to delivery of hydride from 62.101... 

Rearrangements arc common in reactions of sulfur tetrafluoride with acetylenic and allylic alcohols. Highly acidic acetylenic alcohols derived from hexafluoroacetone and other haloacetones react readily at ambient temperature to give fluorinated allenes 10 as the sole... 

Hexafluoroacetone is a reactive electrophile. It reacts with activated aromatic compounds (e.g., phenol), and can be condensed with olefins, dienes, ketenes, and acetylenes. It forms adducts with many compounds containing active hydrogen (e.g., H.,0 or HCN). Reduction of HFA with NaBH or LiAlH affords the useful solvent hexafluoroisopropyl alcohol. The Industrial importance of HFA arises largely from its use 1n polymers and as an... 

Bis(trifluoromethyl)-4,5-difluoro-l,3-dioxole represents the monomer of a new family of amorphous fluoropoiymers (Teflon AF, DuPont) with unusual properties [89JFC(45)100]. Novel fluorinated 2,2-bis(triflu-oromethyl)dioxolanes containing alkyne groups have been synthesized from hexafluoroacetone and propargylic alcohol, bromomethyloxirane, or 1,2-bis(bromomethyl)oxirane [90MI1 91JFC(52)I59] (Scheme 95). 

Organic peroxides such as cyclohexyl or r-butyl hydroperoxide and benzoyl peroxides can oxidize various sulfides to the corresponding sulfoxides where oxidation with TBHP in alcohols or benzene appears to be synthetically useful. 2-Hydroperoxyhexafluoro-2-propanol [(Cp3)2C(OH)OOH], formed in situ from hexafluoroacetone and H2O2, is also a very effective and convenient reagent for this puipose. 4a-Hydroperoxylumifiavin (14) oxidizes sulfides to sulfoxides in organic solvents such as Bu OH or dioxane at 30 C much more effectively than The reactivi of the flavins was... 

The generation of highly fluorinated tertiary alkoxides and alcohols by the use of triniethyl-(trifluoromcthyl)silane and its analogs is most important.A simple, high-yield synthesis of perfluoro(l,l-diniethylethanol) from either hexafluoroacetone or difluorophosgene with trimcthyl(trinuoroniethyl)silaiie probably represents the best overall route to this alcohol to date.""- - " ... 

Resonance-stabilised long-lived carbocations such as 4.26A and 4.26B have been generated from precursor alcohols in superacidic solution [72] but, if conjugative stabilisation is absent as in 4.26C, then only protonated alcohols are observed. Similarly, ketones with up to three a-fluorine atoms can be protonated giving, for example, 4.26D, whilst hexafluoroacetone is not protonated in a superacidic medium [73] (Figure 4.26). 

Reactions with fluoride ion With the exception of CF3OH (see the next section), fluorinated alcohols of the type RpCF20H are not known [124] but complexes of K, Rb, Cs, Ag or (C2H5)4N+ fluorides with hexafluoroacetone have been isolated [125, 126], following from the earlier isolation of some similar complexes with carbonyl fluoride [127]. These complexes have been reasonably formulated as fluorinated alkox-ides (Figure 8.27), but the use of these salts in synthesis is often difficult because the complexes may also act as fluoride-ion donors [128]. 

Recent literature refers to the stereoselective and asymmetric epoxidation of allylic alcohols with organoaluminium peroxides. PhaSiOOH epoxidizes olefins with a stereoselectivity similar to that with peracid. Reports have been made of a-substituted hydroperoxides (acids, esters, ketones, amides, and nitriles) as effective epoxidizing reagents and the application of hexachloroacetone, tetrachloracetone, and hexafluoroacetone hydroperoxide, as well as the HaOa-Vilsmeier reagent system. ... 

W. A. Adam, H.-G. Degen, C. R. Saha-Moller, Regio- and diastereoselective catalytic epoxidation of chiral allylic alcohols with hexafluoroacetone perhydrate. Hydroxy-group directivity through hydrogen bonding, J. Org. Chem. 64 (1999) 1274. 

The group of Masui first attempted the direct epoxidation of olefins by using oxygen and NHPI with metalloporphyrins, but they obtained poor results [15]. Ishii and coworkers proposed two different methods. In the first protocol [16,17], the epoxidizing agent is obtained in situ by the aerobic oxidation of a suitable alcoholic (benzhydrol) compound in the presence of catalytic amounts of NHPI. The resulting oxidant, which is not able to promote the epoxidation by itself, is then activated in the presence of an olefin by catalytic amounts of hexafluoroacetone (HFA) (Scheme 6.1). 

T. Iwahama, S. Sakaguchi, Y. Ishii, Epoxidation of alkenes with H2O2 generated in situ from alcohols and molecular oxygen using N-hydroxyphthalimide and hexafluoroacetone as catalysts. Heterocycles. 52 (2000) 693. 

---