Aromatic fluorine compounds preparation

The preparation of aromatic fluorine compounds may be accomplished by direct fluorination or by fluonnation of organometallic intermediates. Tlte ipso fluorination of an aryl organometallic derivative with a positive fluorine reagent allows control over the regioselectivity of the fluorination and offers advantages in the preparation of F-labeled materials [II, 50],... 

The order of reactivity of the halogens is F2 > Cl2 > Br2 > 12. Fluorine is too reactive to be of practical use for the preparation of aromatic fluorine compounds and indirect methods are necessary (see Section 23-1 OB). Iodine usually is unreactive. It has been stated that iodination fails because the reaction is reversed as the result of the reducing properties of the hydrogen iodide that is formed ... 

G. Balz, G. Schiemann, Aromatic fluorine compounds. I. A new method for their preparation, Chem. Ber. 60 (1927) 1186. 

A. Roe, Preparation of Aromatic Fluorine Compounds from Diazonium Fluoroborates The Schiemann Reaction, Org. React. 1949, 5, 193-228. 

Aromatic fluorinated compounds are of considerable interest for the preparation of biologically active substances. Several fluorination reagents such as CF3OF or F2 require special equipment and experience to handle safely. (CF3S02)2NF (55) is stable for long periods at room temperature and found to be an efficient reagent for nuclear fluorination of aromatic compounds. Typical examples are shown in equation 2939. In addition to the utility in the direct aromatic fluorinations, 55 is also useful in the fluorination of carbon... 

Preparation and Reactions of Polyfluorinated Aromatic Heterocyclic Compounds Yakobson G G, Petrova, T D, Kobnna, L S Fluorine Chem Rev 7, 115-223 285... 

A new thermal preparation ot fluorinated species is copyrolysis Copyrolysis of fluorinated compounds like perfluorobenzene, fluorinated aromatic anhydndes, and fluorinated heteroaromatics with tetrafluoroethylene or other fluonnated olefins is a useful method of preparing fluorinated olefins [88 89], functionalized fluoroaromatics [90 91 92, 93, 94, 95], fluonnated benzocycloalkanes [80, 96, 97, 98, 99, 700], fluorinated heterocycles [80, 93, 101, 102, 103], and fluonnated polycyclic compounds [104] (equations 19 and 20)... 

Aromatic fluoro-compounds have been prepared by thermal cycloaddition of fluorinated 1,3-butadienes 10-12 (Figure 2.1) with several dienophiles. Fluorophenols were obtained by cycloaddition of diene 10 with quinones [11]... 

Among the reductive methods of preparing azoxy compounds is the reduction of aliphatic nitroso compounds with stannous chloride. Triethyl phosphite has been used for the bimolecular reduction of fully fluorinated aromatic nitroso compounds. 

Y.C. Jang and H.K. Sung, Method for preparing a homo-and co-poly-mers by polymerization of cyclic olefin compounds using fluorine-containing aromatic hydrocarbon compound as catalyst activator, US Patent 6998450, assigned to Korea Kumho Petrochemical Co., Ltd. (Seoul, KR), February 14,2006. 

Although the early reactions of perfluoroahphatic and aromatic lithium compounds with various carbonyl compounds gave low yields and mixtures of prod ucts, the current understanding of experimental conditions makes this reaction an attractive means of preparing a variety of fluorine-containing compounds... 

Other interesting fluorinated aromatic telechelic compounds were prepared by Ohsaka et al. [125] ... 

Aromatic fluorination A new method of aromatic fluorination involves treatment of aryltriazenes, readily prepared from aryldiazonium ions and dialkyl-amines, with 70% hydrogen fluoride in pyridine. The yields of product from this reaction are usually higher than those obtained by the reaction of HF-pyridine with a diazonium ion (6, 285) o-methoxy, iodo-, bromo- and nitro-substituted aryltriazenes generally give unsatisfactory yields. This method may be useful for the synthesis of " F-labeled compounds. 

In 1970, unsubstituted valence-bond isomers of benzene were synthesized on a preparative scale and their properties were fully investigated. Since the end of 1960, the chemistry of fluorine compounds was rapidly developed and the photolysis of perfluoro aromatic compound afforded valence-bond isomers in much higher yields than the corresponding hydrocarbon counterparts. These isomers were much more stable than the hydrocarbon analogs and could be used as starting materials for the synthesis of strained compounds. 

The Balz-Schiemann reaction for the introduction of fluorine into an aromatic nucleus involves forming the amine, then the diazonium fluoborate, which in turn decomposes into an aromatic fluoride (104,106,107). One of the reviews (104) of this reaction gives tables of the compounds prepared by this method. 

Fluorine is a small atom with a big ego . It took a very long time for it to be handled with ease since its isolation by Moissan. Carbon was found to be able to give extremely comfortable seats for it as PTFE by Plankett in 1938, and various fluorinated compounds were prepared and commerciahzed. The bonding energy of C-F is 485 kj moD and larger compared with those of C-H (350 kJ mol for aliphatics and 435 kJ mol for aromatics). This basic feature gives remarkable stability to various fluoro compoimds. 

Conversion of diazonium compounds to aryl chlorides, bromides, or cyanides is usually accomplished using cuprous salts, and is known as the Sandmeyer reaction. Since a CN group is easily converted to a CO2H group (eq. 10.13), this provides another route to aromatic carboxylic acids. The reaction with KI gives aryl iodides, usually not easily accessible by direct electrophilic iodination. Similarly, direct aromatic fluorination is difficult, but aromatic fluorides can be prepared from diazonium compounds and tetrafluoroboric acid, HBF4. 

Electrophotographic photoreceptors based on polycarbonate resins have been prepared by treating aromatic dioxy compounds with phosgene [274]. Electrophotographic photoconductors containing fluorine-bearing polycarbonate binders have also been prepared from bisphenol A, phosgene, and 1,1,1,3,3,3-hexafluoro-2,2-bis(4-hydroxyphenyl)propane [275]. 

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