ACID FLUORIDE GROUP

Acid fluoride groups attached to fluorinated alkane groups (—CF2—-COF) absorb at 1900-1870 cm" In the gas phase, acetyl fluoride absorbs at 1869 cm and benzoyl fluoride absorbs at 1820 cm ... 

A cyclic lactone is formed by the reaction of 1,4 diiodo-perfluorobutane with oleum (see Fig. 47). The addition of methanol to the lactone gives selectively 3-methoxycar-bonyl perfluoro-propionyl fluoride, to which hexafluoropropylene oxide is added. After copolymerization with tetrafluoro ethylene, the acid fluoride group is converted to a perfluorovinyl group by pyrolysis. 

Fluorinated ether-containing dicarboxyhc acids have been prepared by direct fluorination of the corresponding hydrocarbon (17), photooxidation of tetrafluoroethylene, or by fluoride ion-cataly2ed reaction of a diacid fluoride such as oxalyl or tetrafluorosuccinyl fluorides with hexafluoropropylene oxide (46,47). Equation 8 shows the reaction of oxalyl fluoride with HEPO. A difunctional ether-containing acid fluoride derived from HEPO contains regular repeat units of perfluoroisopropoxy group and is terminated by two alpha-branched carboxylates. 

Reactions Involving the Trifluoromethyl Group. Aluminum chloride effects chlorinolysis of ben2otrifluoride to give ben2otrichloride (307). High yields of volatile acid fluorides are formed from ben2otrifluoride and perfluorocarboxyUc acids (308). 

During electrochemical fluorination retention of important functional groups or atoms in molecules is essential. Acyl fluorides and chlorides, but not carboxylic acids and anhydrides (which decarboxylate), survive perfluorination to the perfluorinated acid fluorides, albeit with some cyclization in longer chain (>C4) species [73]. Electrochemical fluorination of acetyl fluoride produces perfluoro-acetyl fluoride in 36-45% yields [85]. Electrochemical fluorination of octanoyl chloride results in perfluorinated cyclic ethers as well as perfluorinated octanoyl fluonde. Cyclization decreases as initial substrate concentration increases and has been linked to hydrogen-bonded onium polycations [73]. Cyclization is a common phenomenon involving longer (>C4) and branched chains. a-Alkyl-substituted carboxylic acid chlorides, fluorides, and methyl esters produce both the perfluorinated cyclic five- and six-membered ring ethers as well as the perfluorinated acid... 

The group can be cleaved with mild acid, fluoride ion, or base. ... 

A series of reactions with gases have been selected for the rapid quantification of many of the major products from the oxidation of polyolefins. Infrared spectroscopy is used to measure absorptions after gas treatments. The gases used and the groups quantified include phosgene to convert alcohols and hydroperoxides to chloroformates, diazomethane to convert acids and peracids to their respective methyl esters, sulfur tetrafluoride to convert acids to acid fluorides and nitric oxide to convert alcohols and hydroperoxides to nitrites and nitrates respectively. 

In some cases it is possible to differentiate between the various alkyl substituents. Primary, secondary and tertiary nitrates and nitrites all show clearly different infrared absorptions. The spectra of acid fluorides can be used to differentiate chain-end groups from pendant acid groups. Furthermore, the loss of all -OH species upon sulfur tetrafluoride exposure allows the reliable estimation of ketones, esters and lactones without the complication of hydrogen-bonding induced shifts in the spectra. Preliminary results from the use of these reactions to characterize y-ray oxidized polyethylene and polypropylene are used to illustrate the scope of the methods. 

The synthesis of 3-aryltetrahydroisoquinolines was accomplished by electrophilic aromatic substitution of polysubstituted phenols and phenyl ethers with Lewis acid-generated tosyliminium ions of 2-tosyl-3-methoxytetrahydroisoquinoline derivatives <00SL801>. In addition isoquinoline was reported to react with N-tosylated (R)- or (S)-amino acid fluorides to afford optically active dihydroimidazoisoquinolinones. The reaction proceeds via acylation followed by attack of the tosylamino group at Cl of the intermediate 2-tosylaminoacylisoquinolinium salt <00TL5479>. 

Carbon dioxide has also proven to be an exemplary medium for the polymerization of TFE with perfluorinated alkylvinyl ether monomers containing sulfonyl fluoride such as CF2=CF0CF2CF(CF3)0CF2CF2S02F (PSEVPE). As seen in Table 13.2, the dramatic difference in the number of acid end groups between the commercial sample and those made in C02 indicates that chain-transfer processes stemming from vinyl ether radical arrangement are not nearly as prevalent in C02 as in conventional systems. 

The efficiency of the [2 + 2]-cycloadditions of 417 was utilized in a strategy for the synthesis of cephalosporin derivatives that carry an acetone or acetic acid ester group in the 3-position (Scheme 6.88) [175]. Liberated in the presence of 2-(trimethylsilyl-oxy)propene, 417 underwent cycloaddition leading to 435, treatment of which with tetrabutylammonium or hydrogen fluoride furnished the A3-cephalosporin 436 admixed with the A2-isomer. This mixture was converted to pure 436 by an oxidation-reduction sequence. In addition to the trimethylsilylenol ether of acetone, the... 

FIGURE 5.21 Methods for anchoring an Fmoc-amino acid to the hydroxymethyl group of a linker-resin. (A) 4-Dimethylaminopyridine-catalyzed acylation by the symmetrical anhydride.19 (B) Acylation by a mixed anhydride obtained from 2,6-dichlorobenzoyl chloride.39 (C) Acylation by the acid fluoride.50 (D) Dicyclohexylcarbodiimide-mediated acylation in the presence of 1-hydroxybenzotriazole.52... 

Di-/m-butyl-4-methy I pyridine (3) is hindered, allows coupling of Fmoc-amino-acid fluorides with weak nucleophiles (see Section 7.12) and is best for minimizing the enantiomerizaton of Fmoc-Cys(tBu)-F (see Section 8.1) during its reaction with the hydroxyl group of a linker-resin. 

Group-transfer polymerizations make use of a silicon-mediated Michael addition reaction. They allow the synthesis of isolatable, well-characterized living polymers whose reactive end groups can be converted into other functional groups. It allows the polymerization of alpha, beta-unsaturated esters, ketones, amides, or nitriles through the use of silyl ketenes in the presence of suitable nucleophilic catalysts such as soluble Lewis acids, fluorides, cyanides, azides, and bifluorides, HF. ... 

Much research has been done on the synthesis of perhalogenated P-sultones. The sulfonation of acyclic fluorovinyl ethers leads to a product that is stable up to slightly above room temperature. Thermolysis decomposes the ring structure under SO2 evolution and formation of acid fluorides and perfluorocyclopropane (Eq. 78). )S-Sultones have been synthesized by addition of sulfonyl chlorides to perhalogenated ketones in the presence of triethylamine. The formation of the l-oxa-2-thiacyclobutane 2,2-dioxides appears to require an activated but sterically unhindered carbonyl group because acetone, chloroacetone, trifluoroacetophenone, and p-nitroaceto-phenone did not yield the desired products. ... 

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