Fluorinated ketones, reaction

Replacement of ketones with fluorine by reaction with sulfur tetrafluoride-hy-drogen fluoride, 471... 

In contrast, fluorinated ketones have been used as both nucleophilic and electrophilic reaction constituents The (Z)-lithium enolate of 1 fluoro 3,3-di-methylbutanone can be selectively prepared and undergoes highly diastereoselec-tive aldol condensations with aldehydes [7] (equation 8) (Table 4)... 

Similarly, fluorinated ketones are prepared and react with enamines [50], This reaction involves the intermediacy of an a,P-ethylenic ketone and leads to annelation-aromatization products [5tJ] (Table 13) (equation 37). 

Another reaction that has potential is the intramolecular ene reaction, which preferentially results in five-membered rings Because fluorinated ketones have a propensity for undergoing intermolecular ene reactions [5S], this reaction has tremendous synthetic possibilities Only one example of an ene reaction of an unsaturated trifluoromethyl ketone has been reported, but it indicates the potential of the methodology [59] (equation 59)... 

Kilbardin, A.M., Gazizov, T.K., and Pudovik, A.N., Reactions of diethyl tri-methylsilyl phosphite and of acetyl diethyl phosphite with fluorinated ketones,. Gen. Chem. U.S.S.R., 45,1947,1975. 

The most general and useful application of sulfur tetrafluoride is replacement of carbonyl oxygen and hydroxy groups by fluorine. The reaction has broad scope and is effective with all carbonyl and hydroxy compounds. Alcohols are converted into monofluoro derivatives 1, aldehydes, ketones and quinones into gew-difluoro compounds 2 and 3, and carboxylic acids, acid anhydrides, acid halides and amides into trifluoromethyl compounds 4. 

The fluorine substitution reactions of 4-fluorophenyl ketones can be extended by using alkanc-or arenesulfinates as the sulfur nucleophile, opening access to 4-(alkyl)- or 4-(arylsulfonyl) phenyl ketones 6.14... 

The first attempts to prepare cobalt and nickel ethoxides were reported in 1936 by Meerwein [1102] and Kandelaki [875]. Application ofNaOR in the exchange reactions could not, however lead to the obtaining of the pure products of purpose as they were insoluble in the parent alcohol. Application of LiOR for this purpose permitted Adams et al. in 1966 to obtain the individual M(OMe)2 — derivatives of id-transition elements in the series from Cr to Cu [6]. In the 1980s Mehrotra et al. have described the homologous series of Ni(OR)2 — from methoxide to r-hexyloxide [99], and also Co(OR)2, where R = Me,Et, Pr [1108]. On the alkoxylation of CoH(N2)(PPh3)3 by esters, phenol, or fluorinated ketones, Hayashi et al. [720] have obtained a series of tetrahedral [Co (OR)(PPh3)3] complexes. 

Equilibrium constants for hydration and hemiacetal fonnation have been calculated for representative highly fluorinated ketones.5 Both reactions were substantially more favourable in cyclic than acyclic systems. 

Sanin etal. described the reaction of a,/3-unsaturated fluorinated ketones 88 with ammonium sulfide in ethanol, which led to the formation of thiopyran- Wdioxide derivatives 89 (Equation 28) <1996JOC1986>. However, one of the studied ketones (3-adamantan-2-ylidene-l,l,l-trifluoro-propan-2-one 90) demonstrated an unusual behavior in the course of this reaction, which led to the formation of the fused-ring thietane 31 in 86% yield (Equation 29) <1996JOC1986>. 

Highly fluorinated ketones such as hexafluoroacetone are oxidation catalysts even when H2O2 is used as an oxygen source. In this case, the reaction probably involves an a-hydroxyhydroperoxide, rather than a dioxirane, and the reactions require more drastic conditions (402, 403). Nevertheless, the observations demonstrate that fluorinated ketones are useful catalysts for activation of oxidants. 

For instance, the telechelic diols were prepared from phenol, a fluorinated ketone and HF according to the following reaction ... 

Reaction of Dibromodifluoromethane and tris(Dimethylamino)phosphine with Fluorinated Ketones... 

The rates at which several substituted benzenes quench triplet benzophenone have been measured 17 8). No single linear free energy relationship can be derived. For alkoxybenzenes, alkylbenzenes, benzene itself, and benzotrifluoride as quenchers, one finds a linear plot of log vs. IP with a slope similar to that found for the plot of all substituted benzenes and triplet a-trifluoroacetophenone. A given aromatic such as benzene quenches the fluorinated ketone triplet, which has an E - -E(A /A) value of only 16 kcal, some 50 times faster than it quenches triplet acetophenone or benzophenone 132>. This rate difference reflects only 20% of the full 12 kcal difference in thermodynamic redox potentials. However, the halobenzenes and benzonitrile quench triplet benzophenone faster than does benzene 178>. It seems likely that with these electron poor benzene derivatives, some alternate chemical reaction becomes dominant. Although a reverse CT process has been suggested, with the triplet ketone as donor, it is perhaps more likely that some sort of radical addition occurs with conjugating substituents on... 

In the reaction of a-(trihalomcthyl)sulfanyl ketones with hydrogen fluoride,, -difluoroalkyl fluoridothiocarhonates 14 are obtained instead of the expected trifluoromethyl sulfides.The reaction is thought to proceed via an initial chlorine-fluorine exchange reaction followed by rearrangement into the /i-difluorinated product. 

Because of the ready reaction of fluorinated ketones with nucleophiles there is a considerable literature on this subject, although it is dominated by that of hexafluoroacetone. Burger and co-workers have prepared a variety of heterodienes, 8.11A (Figure 8.11), from hexafluoroacetone and developed an extensive chemistry of these derivatives, especially the formation of heterocycles [95, 96]. 

Some unusual reactions can occur between fluorinated ketones and trialkylphosphines [117] or trialkylphosphites [118] (Figure 8.22). 

The primary act for the photochemical decomposition of trifluoroacetophenone (ref. 589) at A 3130 A is believed to be predominantly of Type 1, with the formation of benzoyl and trifluoromethyl radicals. On the other hand, a primary act of Type 2 has been proposed by Pritchard and Thommarson for the photolysis of hepta-fluoropropyl ethyl ketone. Studies on the photolysis of these and other fluorinated ketones showed many features in common with that of trifluoroacetone, but have also led to some interesting observations on radical-radical interactions. For example, Pritchard et identified the following reactions (leading to the formation of vinyl fluoride) during the photolysis of 1,3-difluoroacetone... 

Alcock and Whittle had previously reported on a similar reaction involving CF3 and CH3 radicals, but Pritchard and Bryant ° > ° showed that the related reaction between CF2H radicals was of little importance during the photolysis of 1,1,3,3-tetrafluoroacetone. Robb et alP have discussed the cage effect in the liquid-phase photolysis of fluorinated ketones. 

Hexafluoroacetone has been a popular compound for further photochemical study" " Majer et al. have reported on the photolysis of alicyclic perfluoroketones and of chloropentafluoroacetone other work on fluorinated ketones has been reported by Pritchard et a/. - , by Phillips and Trotman-Dickenson , and by Schuster and Patel . Intramolecular elimination reactions in the photolysis of fluoroaldehydes have been discussed by Morris and Thynne and by Pritchard and Perona . Photolytic studies on other oxygen-containing halogen compounds have included chloroacetic acids , acetyl chloride , perfluoroacyl fluorides , CF3OF and CF3OOCF3 . 

Cyanoformamidines, exhibiting nucleophilic and electrophilic properties in the 1,3-positions, react with hexafluoroacetone forming five-membered heterocycles (86CB2127). This ability to form five-membered heterocycles is the major characteristic of hexafluoroacetone, which is also inherent in some perfluorinated and partially fluorinated ketones, aldehydes, and imines in their reactions with a-functional derivatives of carboxylic acids, as well as w-amino, a-N-alkylamino,... 

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