Tertiary amines, fluorinated

Many perfluoroaUphatic ethers and tertiary amines have been prepared by electrochemical fluorination (1 6), direct fluorination using elemental fluorine (7—9), or, in a few cases, by fluorination using cobalt trifluoride (10). Examples of lower molecular weight materials are shown in Table 1. In addition to these, there are three commercial classes of perfluoropolyethers prepared by anionic polymerization of hexafluoropropene oxide [428-59-1] (11,12), photooxidation of hexafluoropropene [116-15-4] or tetrafluoroethene [116-14-3] (13,14), or by anionic ring-opening polymeriza tion of tetrafluorooxetane [765-63-9] followed by direct fluorination (15). 

Carbonyl sulfonyl fluorides of the formula FC0(CF2) S02F have been prepared by electrochemical fluorination of hydrocarbon sultones (41,42). More commonly in a technology pioneered by Du Pont, perfluoroalkanecarbonyl sulfonyl fluorides are prepared by addition of SO to tetrafluoroethylene followed by isomerization with a tertiary amine such as triethylamine (43). 

The fluoraza reagents consist of two types of compounds one in which a fluorine atom is bound to the nitrogen atom of an amide or, more often, a sulfonamide and one in which a fluorine atom is bound to the nitrogen atom of a tertiary amine such as pyridine, quinuclidine, or triethylenediamine 1,4-diaza-bicyclo[2 2.2]octane. The positive charge on the nitrogen is counterbalanced by a non-nucleophilic anion such as triflate or tetrafluoroborate. 

The term fluorous was coined as an analogy to aqueous for highly fluorinated alkanes, ethers and tertiary amines [1], These compounds differ markedly from the corresponding hydrocarbon compounds to the extent that such compounds commonly give bilayers with conventional organic solvents. In this chapter, we will discuss the different approaches towards carrying out reactions in fluorous media and describe how reactants and catalysts can be engineered to be preferentially soluble in fluorous solvents. 

In the reaction of 1-naphthol with 3-nitro-4-fluorobenzalmalononitrile in ethanol, catalyzed by secondary amines, nucleophilic displacement of fluorine competes with pyran ring closure. Application of a tertiary amine (N-methylmorpholine) leads to the selective formation of the corresponding aminochromene (94H(38)399). 2,3-, 1,8-Dihydrooxynaphthalenes 148 and 149 react with 1 or 2 equiv. of aromatic aldehyde 28 and MN 27a to yield naphthopyrans 150 and 151 or dipyrans 152 and 153 (90IJB885, 02RCB2238) (Scheme 53). 

Hydrogen atoms bonded to nitrogen, as well as those attached to carbon, are replaced by fluorine upon perfluorination of primary and secondary amines (Fig. 37) [101, 102]. Perfluorinated tertiary amines have also been prepared (Figs. 38 and 39) [78,103]. 

In the course of their work on suitable materials for use as blood substitutes the group at the University of Padua have studied the electrochemical fluorination of cyclic tertiary amines [80]. The ECF of NW-diethylcyclohexylamine and N-ethyldicyclohexylamine gave the corresponding perfluoroamines together with several other compounds arising from incomplete fluorination and fragmentation reactions. 

While aromatic amines are discussed in Section 5.2.14., various data for aliphatic amines are listed in Table 20. It is worthwhile remembering that tertiary perfluorinated amines, such as perfluorotributylamine. are completely stable, inert and nontoxic compounds, while some partially fluorinated tertiary amines tend to be unstable, eliminating hydrogen fluoride even at low temperature and are therefore toxie. Primary and secondary aliphatic fluorinated amines carrying CF,N groups have not, so far, been isolated due to their instability. 

Perfluoropropene (1) can be directly oxidized to perfluoro-1,2-epoxypropane (2) by a variety of oxidizing reagents, e.g. oxygen, hydrogen peroxide.50 s2 Pcrfluoro-1,2-epoxypropane (2) can fluorinate carboxylic acids to their corresponding acid fluorides in the presence of tertiary amines.52 55... 

All three compounds (WF6 and MoF6 are best) will bring about a reaction (not a fluorination) that may have synthetic utility at 0CC in l,l,2-trichloro-l,2,2-trifluoroethane (Freon 113) or chloroform they will cleave N,TV-dimethyl- and N-tosylhydrazones and oximes back to the parent carbonyl compounds12,14 (UF6 converts any first-formed aldehydes into acid fluorides1213). All three hexafluorides will convert1215 tertiary amines into carbonyl compounds and carboxylic acids into acid fluorides.16 They also dope polyacetylene to the metallic regime.17... 

To fully interpret these details, it is necessary to refer to the User s Guide. X refers to a halogen other than fluorine Y refers to a polar fragment Fragbranch refers to the unique lowering of the hydrophobicity of chains radiating from phosphate, phosphonate, and tertiary amine fragments. The three X-C-X factors are the same as seen in chloroform the... 

Amines. The synthesis of fluorinated ethyl amines has been accomplished 96 by heating CHF2CH2I to 130° in a sealed tube with concentrated aqueous ammonia a mixture of the primary amine, CHF2CH2NH2, secondary amine, (CHF2CH2)2NH, and tertiary amine, (CHF2CH2)3N, is obtained. 

In the presence of alkaline metal fluorides or tertiary amines, perfluoro-olefins react with fluorine-containing keteneimines to form azetidines 25 in mild conditions (76IZV1813). The role of the catalyst seems to be the transformation of the electrophilic keteneimine into the nucleophilic mesomeric anion capable of adding at the multiple bond of the perfluoro-olefin. The addition is accompanied by cyclization generating a catalyst. 

With primary amines, aminotetrafluorophosphoranes are formed only if R is a bulky organic group or an aromatic group in the presence of a tertiary amine. Otherwise, cyclic dimers [F3PNR]2 are formed. Fluorination of P(NMe2)3 with sulfhr tetrafluoride yields triaminodifluorophosphorane, F2P(NMe2)3. ... 

Conversely, fluorine or fluorocarbon groups have a major effect in reducing the base strength of amines, ethers and carbonyl compounds for example, 2,2,2-trifluoroethylamine (pKb = 3.3) is ca. 10 times less basic than ethylamine. Also, pentafluoropyridine is only protonated in strong acid [6], whereas hexafluoroacetone is not protonated even in superacids [7-9] and perfluorinated tertiary amines and ethers are sufficiently non-basic for them to be used as inert fluids interchangeably with perfluorocarbons. 

Perfluoro tertiary amines (Rf)3N are very inert systems and are more akin to perfluoro-alkanes than amines. They are most directly obtained by electrochemical fluorination [272, 273] (see Chapter 2, Section 111) and, as inert volatile fluids, they are used commercially as evaporation coolants for electronic apparatus. 

Tertiary amine trishydrofluorides are stable complexes, very convenient for the delivery of hydrogen fluoride. They can be distilled in vacuo, and are suitable reagents for the nucleophilic replacement reactions of chlorine by fluorine under mild homogeneous conditions. The reaction of COCl, with Et3N.3HF [680] in dry ethanenitrile at room temperature proceeds quantitatively according to ... 

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