Tables fluoroacetates

Both methyltriethylphosphonium fluoride and methyltributylphospho-nium fluoride have been prepared The latter generates benzyl fluoride from benzyl chloride in 80% yield and ethyl fluoroacetate from ethyl bromoacetate in 53% yield Methyltnbutylphosphonium fluoride converts 1-bromododecane to a 50 50 mixture of 1-fluorododecane and 1-dodecene Methyltnbutylphosphonium fluoride also quantitatively forms styrene from 1-bromo-1-phenylethane [26] Methyl-tnbutylphosphonium fluonde is the reagent of choice for the conversion of N,N dimethylchloroacetamide to its fluoride, but it is not able to convert chloro-acetonitnle to fluoroacetomtrile Methyltnbutylphosphonium fluoride changes chloromethyl octyl ether to the crude fluoromethyl ether in 66% yield The stereoselectivity of methyltnbutylphosphonium fluoride is illustrated by the reac tions of the 2-tert-butyl-3-chlorooxiranes [27] (Table 2)... 

Alkyl diethylphosphononuoroacetates have been used extensively in ol fi-nanon procedures [69], principally forming the ffJ-a-fluoro-a.P-unsaturated esters with very high stereoselectivity [70] (equation 61) (Table 22). Preparation of the ethyl diethylphosphonofluoroacetate from ethyl fluoroacetate has obviated the necessity to prepare ethyl bromofluoroacetate from bromine fluoride and ethyl diazoacetate [71],... 

Table 23. Preparation of Ethyl Alkylidene Fluoroacetates RCH=CFCOOEt from Esters Reduced in situ with Diisobuty laluminum Hydride [73]...

For synthetic purposes, aldol-rype condensations of aldehydes with esters or amides are potentially of great utility because the carbonyl group is easily transformed either by further additions or by oxidation or reduction. Deprotonation of an ester [7, 19, 20] or amide of fluoroacetic acid [9, 27] has led to aldol condensations in high yields (equation 17) (Table 7)... 

Table 7. Products of the Directed Aldol Reaction of Lithium Enolate of Ethyl Fluoroacetate [/S, 19 ...

Interest centers on fluoroacetic acid itself,54-55,56 115 but its monofluorinated homologs have been equally studied to attempt to verify the observation that only compounds CFH2(CH2)nC02H with n = 0 or even numbers, and their derivatives (esters, salts) show considerable toxicity (Table 11) in addition to that of their acid function. In the course of in vivo metabolism these fluorinated derivatives end up, like any fatty acid by /(-oxidation or hydrolysis, as the toxic fluoroacetic acid. With an uneven number of n, metabolism stops at the stage of the less toxic 2-fluoropropanoic acid (CFH2CH2C02H). 

Table 2. Yields from the Direct Thallation of Aromatic Compounds with Thallium(III) Tri-fluoroacetate...

Table 23. Preparation of Ethyl Alkylidene Fluoroacetates RCU=CFCOOEt...

In deuterium oxide, the parent substance, 8-azapurine (neutral species), showed two peaks at r 0.32 and 0.80 (1H each) corresponding to the two aromatic-type protons in the 6- and 2-positions, respectively (see Table I). The anhydrous cation was easily demonstrated in tri-fluoroacetic acid, through the downfield displacement of these signals by the usual 0.4-0.6 ppm. However in deuterium oxide-deuterium... 

As with the Henry nitro-aldol condensation, the modified Dakin-West acylation is primarily used for synthesis of trifluoromethyl ketones, although there are several examples of its use in the synthesis of fluoromethyl ketones (Table 3).[31314 The modified Dakin-West reaction utilizes fluoroacetic anhydride (or other appropriate anhydrides) to form an anhydride, which then undergoes cyclization, activation of the a-carbon, and acylation at the a-carbon the precise details of this method will be discussed in Section 15.1.4.3.1. 

Variations of the biological activity are not necessarily linked to the induction of effects at the level of a given receptor, but could have come from a pharmacokinetic factor (urinary or biliary excretion, plasma protein binding, differential metabolism). A case of differential metabolism is illustrated by the comparison of the toxicities of odd and even u>fluoro acids. " The (3-oxidation of odd chain length compounds leads to the extremely toxic fluoroacetic acid, while that of the acids with even numbers of carbon atoms generates 3-fluoropropionic acid which is clearly less toxic (Table 14.3). 

It has been suggested that trialkylborane initiators form a complex with the radical end95. This has been shown by comparing the activation parameters for the tri-n-butylborane-initiated polymerization of vinyl trimethylacetate and of vinyl tri-fluoroacetate in various solvents with those for the AIBN-initiated polymerization (Table 2). The difference of stereoregulating activation parameters between the initiators may be due to the solvent effect on the formation of a complex of trialkylborane with the radical end. 

In the rearrangement of allyl fluoroacetates, trialkylsilyl triflates have been introduced as a new reagent for the Z-selective generation of silyl ketene acetals485. Thus, when (T)-crotyl fluoroacetates are treated at ambient temperatures with a trialkylsilyl triflate in the presence of a tertiary amine, rearranged products with a svn relationship are preferentially obtained. The ketene acetal intermediates cannot be isolated and the geometry has been deduced from the stereochemistry of the products. The selectivity of this process improves in the order triisopropyl > ferf-butyldimethylsilyl > rerf-hexyldimethylsilyl > trimethylsilyl a triethylsilyl (see Table 11). 

See also Intermediates of the Citric Acid Cycle, Figure 14.3, Table 14.1, Fluoroacetate, Fluorocitrate... 

Fluoroacetic acid occurs in a South African plant Dkhapetalum, and has killed many cattle in that country. The toxic action of fluoroacetic acid does not depend on any chemical reactivity on the part of fluorine, but on the small size of the fluorine atom (Table 9.1) (Bartlett and Barron, 1947), which deceives the earlier, poorly discriminating enzymes into treating it as a hydrogen atom whereas the later enzymes have more inbuilt precision. Fluoroacetic acid, which is used to exterminate rabbits in their burrows, is not very selective and presents a hazard to human beings. 

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