Fluorine substitution reactions

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... 

Replacement of Hydrogen. Three methods of substitution of a hydrogen atom by fluorine are (/) reaction of a G—H bond with elemental fluorine (direct fluorination, (2) reaction of a G—H bond with a high valence state metal fluoride like Agp2 or GoF, and (J) electrochemical fluorination in which the reaction occurs at the anode of a cell containing a source of fluoride, usually HF. 

Treatment of coal with chlorine or bromine results in addition and substitution reactions. At temperatures up to 600°C chlorinolysis produces carbon tetrachloride, phosgene, and thionyl chloride (73). Treatment with fluorine or chlorine trifluoride at atmospheric pressure and 300°C can produce large yields of Hquid products. 

Kinetics of Nucleophilic Substitution Reactions of Polyfluoroaromatic Compounds Rodionov, P P, Furin, G G J Fluorine Chem 47. 361 34 105 ... 

Fluonde Ion as Nucleophile and a Leaving Group in Aromatic Nucleophilic Substitution Reactions Vlasov V M J Fluorine Chem 6i. 193-216 77... 

Rate constants have been measured for the reactions of boron compounds with a series of bromomethanes and bromofluoromethanes. Previously it was shown that the reactivity of the chlorine in chlorofluoromethane is substantially reduced by increasing fluorine substitution. The corresponding decrease in the reactivity of bromolluoromethane u as not observed [ifS]. 

Fluorine-substituted heterodienes are particularly prone to inverse electron demand Diels-Alder reactions with electron-rich dienophiles, as can be seen from the examples in equations 94-97 [113, 114, 115, 116, 117]... 

The common side reaction in most thermal studies of fluorine-substituted cyclopropanes is difluorocarbene extrusion Increasing the number of fluonne substituents on the cyclopropane ring significantly increases the rate of difluorocarbene extrusion [135, 136, 137]... 

The course of each of the free radical reactions shown in equations 19-21, where fluorine substitution alters the normal trans stereochemistry of addition, is ascnbed to endo fluonne stenc effects... 

The most common types of aryl halides in nucleophilic aromatic substitutions are those that bear- o- or p-nitro substituents. Among other classes of reactive aryl halides, a few merit special consideration. One class includes highly fluorinated aromatic compounds such as hexafluorobenzene, which undergoes substitution of one of its fluorines on reaction with nucleophiles such as sodium methoxide. 

Chlorine and iodine can be introduced into aromatic rings by electrophilic substitution reactions, but fluorine is too reactive and only poor yields of monofluoro-aromatic products are obtained by direct fluorinafion. Aromatic rings react with CI2 in the presence of FeCl3 catalyst to yield chlorobenzenes, just as they react with Bi 2 and FeBr3. This kind of reaction is used in the synthesis of numerous pharmaceutical agents, including the antianxiety agent diazepam, marketed as Valium. 

The reaction of tetramethylsilane with fluorine led to the isolation of several, partially fluorine-substituted tetramethylsilanes (see Tables VII-IX), and preservation of over 80% of the silicon-carbon bonds in the initial, tetramethylsilane reactant. The stability of many of the partially fluorinated germanes and silanes (some are stable to over 100°C) is very surprising, for the possibility of elimination of hydrogen fluoride is obvious. Indeed, before the first reported synthesis (12) of... 

The presence at the catalyst s surface of active sites which made possible the dehydrofluorination reaction (C-F rupture) and the chlorine-fluorine substitution (C-Cl rupture) was then supposed There would also exist active sites which would only allow the second reaction (C-Cl nipture). The addition of nickel, by suppressing the sites which allow the two reactions (fluorination and dehydrofluorination) decreases the total activity. 

Nucleophilic substitution reactions involving the replacement of chlorine (or bromine or fluorine) atoms on the phosphorus have been among the most well studied reactions of cyclophosphazenes... 

In a comparative study of fluorination of l,2 3,4-di-0-isopropyli-dene-6-O-p-tolylsulfonyl-a-D-galactopyranose with tetrabutylammonium fluoride in a variety of dipolar, aprotic solvents (as well as 1,2-eth-anediol, in which no reaction was observed), acetonitrile was found to give the highest proportion of substitution of the sulfonic esters relative to their elimination.106 Elimination is the major, competing reaction in these nucleophilic-substitution reactions, because of the high basicity and low nucleophilicity of the fluoride ion or, in terms of the... 

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