Electrophilic fluorinating agent

Fluorinated olefins, 77 866 Fluorinated organics, production of, 77 847 Fluorinated polyimides, 20 278 Fluorinated thermoplastics, 10 8 Fluorinated titanocycle, 25 118 Fluorinating agents, electrophilic, 77 847 Fluorination, 9 281, 678-679 aromatic ring, 77 866 chlorocarbons, 6 235 direct, 77 864, 882 electrochemical, 77 864—865, 882 of germanium, 72 552 halogen exchange, 77 861-864 selective, 77 831... 

A comparison of the yields of para-substituted [18F]fluoroarenes indicate that (i) acetyl hypofluorite is an inferior fluorination agent for the fluorodegermylation reaction and (ii) the aromatic substituents have considerable influence over the reactivity of the fluorination. A decrease in the fluorodegermylation yield was observed with electron-withdrawing aromatic substituents. The electrophilic aromatic degermylation reaction is thought to proceed via a cr-complex intermediate (Scheme 3). It has been hypothesized that the yield of aryl fluoride is influenced to some extent by the aromatic substituents ability to stabilize the cr-complex intermediate. 

Electrophilic fluorinating agents, 77 847 Electrophilic quench, 72 828 Electrophilic reactions... 

In this section the production of a number of radioactive electrophilic fluorination agents that have not already been dealt with in Section 2.6 will be discussed. 

In principle, two mechanisms involving either one or two-electron transfer from the aromatic substrate to fluorine may occur and, in practice, the mechanism of fluorination of any given aromatic molecule probably lies between these two extremes. The distinction between electron transfer (Path A, Fig. 55) and SN2-type processes (Path B, Fig. 55) in reactions between various electrophilic fluorinating agents and nucleophiles has been addressed by Differding [144, 145] but these principles can also be applied to reactions involving elemental fluorine. 

Perfluoro-l-fluoropiperidine (1) is synthesized by the Simons electrochemical fluorination process (8% from pyridine,20 13% from 2-fluoropyridine21). It is a seemingly innocuous liquid (bp 49.5 °C) which holds the distinction of being only the second compound to be identified as an electrophilic fluorinating agent. It decomposes rapidly at 50-70°C. 

It has been shown that 1-fluoroquinuclidinium fluoride (NFQNF, 2), one of the more successful N-F fluorinating agents, can fluorinate a wide array of electron-rich substrates.73,84-86 NFQNF (2) acts as a site-selective electrophilic fluorinating agent towards carbanionic substrates.73-75... 

Among the fluorinating agents of practical significance,44 only fluoroxytrifluoro-methane45 and iV-fluoroperfluoroalkylsulfonimides46 were shown to fluorinate aromatic hydrocarbons by an electrophilic mechanism. 

AN ELECTROPHILIC FLUORINATING AGENT (Pyrldlnlum, 1-lluoro-, salt with trifluoromethanesulfonlc acid (1 1))... 

There are two types of hypofluorite compounds that have been prepared, the perfluoroalkyl hypofluorites, such as CF3OF, and the acyl hypofluorites, such as CH3C02F. The fluorines of such compounds are very deshielded and thus have significantly positive chemical shifts (Scheme 7.15). Also shown is the powerful electrophilic fluorinating agent, perchloryl fluoride. 

Table 5. Electrophilic fluorinating agents and their electrochemical reduction potentials (Ep).

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