Fluonnation of carbon

The reaction of diethyl tartrate with sulfur tetrafluonde at 25 °C results in replacement of one hydroxyl group, whereas at 100 °C, both hydroxyl groups are replaced by fluonne to form a,a -difluorosuccinate [762] The stereochemical outcome of the fluonnation of tartrate esters is retention of configuration at one of the chiral carbon atoms and inversion of configuration at the second chiral center [163,164, 165] Thus, treatment ofdimethyl(+)-L-tartrate with sulfur tetrafluonde gives dimethyl meso-a,a difluorosuccinate as the final product [163, 164], whereas dimethyl meso tartrate is converted into a racemic mixture of D- and L-a,a -difluorosuccmates [765] (equation 80)... 

Primary alkyl chlorides are fairly stable to fluorine displacement. When fluonnated, 1-chloropropane is converted to 1-chloroheptafluoropropane and 1-chloro-2-methylbutane produces 39% l-chlorononafluoro-2-methylbutane and 19% perfluoro-2-methylbutane. Secondary and tertiary alkyl chlorides can undergo 1,2-chlonne shifts to afford perfluormated primary alkyl chlorides 2-Chloro-2-methylpropane gives l-chlorononafluoro-2-methylpropane, and three products are obtained by the fluonnation of 3-chloropentane [3] (equation 1). Aerosol fluonna-tion of dichloromethane produces dichlorodifluoromethane which is isolated in 98% purity [4] (equation 2). If the molecule contains only carbon and halogens, the picture is different. Molecular beam analysis has shown that the reaction of fluorine with carbon tetrachloride, lodotrichloromethane, or bromotrichloromethane proceeds first by abstraction of halogen to form a trichloromethyl radical [5]... 

A number ol aryl trifluoromethyl ethers are synthesized by fluonnation of aryl chlorotkioformates with molybdenum hexafluoride. The reagents are progressively heated from -25 to 130 °C, and the products are distilled off. Molybdenum disulfide and carbon disulfide are the by-products [12] (equation 16)... 

Benzyl and alkyl tnalkylsilyl ethers undergo clean fluonnation to give good yields of benzyl and alkyl fluorides, respectively, when reacted with a combination of d quaternary ammonium fluoride and methanesulfonyl orp- toluenesulfonyl fluoride. The reactions are applicable strictly to a primary carbon-oxygen bond, secondary and tertiary alkyl silyl ethers remain intact or, under forcing conditions, aie dehydrated to olefins [29] (equation 22)... 

Hydroxylation, the addition of two hydroxyl groups across a double bond, converts fluonnated alkenes to different products depending on the presence or absence of a fluorine atom at the hydroxylated carbon... 

Fluonnated ylides have also been prepared in such a way that fluonne is incorporated at the carhon P to the carbamonic carbon Vanous fluoroalkyl iodides were heated with tnphenylphosphine in the absence of solvent to form the necessary phosphonium salts Direct deprotonation with butyUithium or hthium dusopropy-lamide did not lead to yhde formation, rather, deprotonation was accomparued by loss of fluonde ion Flowever deprotonation with hydrated potassium carbonate in thoxane was successful and resulted in fluoroolefin yields of45-S0% [59] (equation 54) P-Fluorinated ylides may also be prepared by the reaction of an isopropyli-denetnphenylphosphine yhde with a perfluoroalkanoyl anhydnde The intermediate acyl phosphonium salt can undergo further reaction with methylene tnphenylphosphorane and phenyUithium to form a new yhde, which can then be used in a Wittig olefination procedure [60] (equation 55) or can react with a nucleophile [6/j such as an acetyhde to form a fluonnated enyne [62] (equation 56)... 

The nucleophilic attack of nitrogen bases leads to a variety of products as the result of addition or addition-elimination reactions The regioselectivity resembles that of attack by alcohols and alkoxides an intermediate carbanion is believed to be involved In the absence of protic reagents, the fluorocarbanion generated by the addition of sodium azide to polyfluonnated olefins can be captured by carbon dioxide or esters of fluonnated acids [J 2, 3] (equation I)... 

Carbon dioxide may be eliminated even from the ester of a fluonnated acid by using lithium chlonde-hexamethylphosphonc tnamide complex at reflux temperature The intermediate carbene is formed in 78-90% yield [96, 97] (equation 64)... 

The effects of a- vs. P-fluonnation imply that fluoroolefms normally react regioselectively with electrophiles to minimize the number of fluorines p to the electron-deficient carbon in the transition state. Diverse types of electrophilic additions follow this rule (equations 6-8, for example), although there aie exceptions, especially for ionic addiPons of halomethanes to fluoroolefins [124]... 

One-carbon fluonnated compounds are used as synthetic reagents and in many theoretical inquines of structure and spectroscopy Twenty fluorohalomethanes are listed in Table 1 [56, 57, 58 59, 60, 61, 62] Fluorocarbons llBl, 22B1, and 31B1 and 12 of 15 lodofluoromethanes are not listed because of a lack of NMR data Most of the if-F values are taken from the older literature [57, 59], obtained from... 

Incorporation of fluorine into a biological substrate opens a spectral window for viewmg biomolecular structure and dynamics in solution With mmimal background mletference, fluonne NMR can provide clear spectral information for fluorme conlainmg macromolecules, in contrast to an indecipherable mass of signals from proton or carbon NMR Whether the fluonnated unit is termed a probe, tag, marker, or reporter group, its function is the same to act as a beacon of spectral information... 

The word fluorocarbon has been used here in a generic way to indicate completely fluonnated liquids, including ethers and amines, rather than in its stricter meaning of having only carbon and fluorine atoms The definition of the word perfluori-nated is somewhat vague, because it can include compounds that retain double bonds or protons... 

Tnfluoromethyl hypofluonte will fluonnate Schiff bases, giving 7V,a,a-tn-fluoroamines and a-fluoroirmnes [144] and reacts with diazoketones to give adducts in modest yields [145] (equation 6) A-Substituted anridines give nng opened products by 1,3 addition of fluonne on nitrogen and tnfluoromethoxy on carbon [146] (equation 7)... 

Highly fluonnated alkanes are also reduced by alkali metals Lithium amalgam converts polytetrafluoroethylene to a carbon polymer composed of monolayer ribbons of six membered nngs with lithium atoms bound to the edges [3]... 

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