Benzo fluorine

Benzo[/]flavone conformation, 3, 623 Benzo[g]flavone conformation, 3, 623 Benzofuran fluorinated... 

Strong acids or superacid systems generate stable fluorinated carbocations [40, 42] Treatment of tetrafluorobenzbarrelene with arenesulfonyl chlorides in nitro-methane-lithium perchlorate yields a crystalline salt with a rearranged benzo barrelene skeleton [43] Ionization of polycyclic adducts of difluorocarbene and derivatives of bornadiene with antimony pentafluonde in fluorosulfonyl chloride yields stable cations [44, 45]... 

The usual order found with halogenonitrobenzenes is F > Cl Br I, the order of Cl and Br being variable, just as in heteroaromatic reactivity. The position of fluorine is of interest the available data indicate that it is usually the same as for nitrobenzene derivatives. Thus, in acid hydrolysis the order F > Cl for 2-halogeno-quinolines can be deduced beyond doubt since the fluoro derivative appears to react in the non-protonated form and the chloro derivative to resist hydrolytic attack even in the protonated form under appropriate conditions (Section II,D, l,d). Furthermore, in the benzo-thiazole ring, fluorine is displaced by the CHgO reagent at a rate 10 times that for chlorine. ... 

There are several new methodologies based on the Julia olefination reaction. For example, 2-(benzo[t/Jthiazol-2-ylsulfonyl)-j -methoxy-i -methylacetamide 178, prepared in two steps from 2-chloro-iV-methoxy-jV-methylacetamide, reacts with a variety of aldehydes in the presence of sodium hydride to furnish the ajl-unsaturated Weinreb amides 179 <06EJOC2851>. An efficient synthesis of fluorinated olefins 182 features the Julia olefination of aldehydes or ketones with a-fluoro l,3-benzothiazol-2-yl sulfones 181, readily available from l,3-benzothiazol-2-yl sulfones 180 via electrophilic fluorination <06OL1553>. A similar strategy has been applied to the synthesis of a-fluoro acrylates 185 <06OL4457>. 

Anodic regioselective fluorination of a-phenylsulphenylated ethyl acetates, 1-naphthalene and 2-pyridine derivatives [80], l-aryl-3-(phenylthio)oxindoles and 2-substituted-3-oxo-4-(phenylthio)-l, 2, 3,4-tetrahydroisoquinolines [81], 2-benzo-thiazolyl and 5-chloro-2-benzothiazolyl sulfides [82], a-(phenylsulfenyl)lactams [83], as well as various heterocycles such as thiolanones, oxathiolanones, dithi-olanones, 3Fl-l,4-benzoxathian-2-ones [84] in Et3N-3HF or Etr NF- HF [n = 3,4), has been reported. 

Electrophilic substitution in benzo[fe]thieno- and benzo[fe]furo-[2,3-c]pyridines (2) occurs mainly at the 6-position, although when this position is blocked by Cl in a related structure 5-,7-, and 8-substituted products are formed. The usefulness of triflu-oromethanesulfonic acid as a new solvent with CFCI3 for the reaction of fluorine with aromatics has been explored. Fluorobenzene gives 1,4-difluorobenzene (31%) and 1,2-difluorobenzene (7%) instead of the addition products mainly observed when the acid is absent 1,2- and 1,3- but not 1,4-difluorobenzene undergo further substitution at appropriate acidity. 

Benzo[a]anthracene [56-55-3] Benzo[6 A]fluoranthene [NA] Benzo[ Ai]fluoranthene [203-12-3] Benzo[a]fluorine [238-84-6]... 

Research on the fluorination of aromatic amines has provided access to 4-fluoro-2,l,3-benzo-thiadiazole (77). Treatment of 4-amino-2,l,3-benzothiadiazole (1) with nitrosonium tetra-fluoroborate (NOBF4), followed by heating of the resulting diazonium salt, gave the aryl fluoride (77) in 23% yield <92SC73>. 

Unlike 36, 37 is not carcinogenic because the fluorine atom at position 1 blocks bioactivation of the 1,2-position and, hence, the 1,2-epoxide metabolite is not formed [74]. Replacement of the hydrogen atom at position 2 of 36 with a fluorine atom also abolishes carcinogenicity [74]. Similar observations have been made with fluorine substitution of specific hydrogen atoms of other anthracenes, and of other polyaromatic compounds such as chrysenes and benzo[a]pyrenes [75]. 

The sulfur tetrafluoride fluorination of most nonhalogenated quinones and hydroxyquinones is erratic in behavior and generally occurs with isomerization, substitution of a hydrogen atom by fluorine, and addition of fluorine to the carbon atom / to the carbonyl group. Thus, the fluorination of benzo-l,4-quinone results in aromatization to give 1,2,4-trifluorobenzene (8) as the sole product.41... 

Ring fluorination of pyridine and its benzo derivatives is suggested to occur through nucleophilic attack of fluoride ion on an initial pyridine fluorine complex (87TL255, 91BCJ1081, 93AHC(58)29l). In electron-deficient pyridines and their benzo derivatives, fluorination on the pyridine ring is kinetically competitive with annular and side chain fluorination. 

The first successful Diels-Alder addition of thiophene appears to have been with tetrafluorobenzyne (66CC143). The adduct apparently loses sulfur, resulting in the isolation of the tetrafluoronaphthalene in 40% yield (Scheme 78). Other thiophene derivatives (69T25) and fluorinated benzynes <71JCS(C)604) have been similarly reacted. Subsequently it was found (80H 14)647) that unsubstituted benzyne, generated from diphenyliodonium-2-carboxylate, could be trapped with thiophene to form naphthalene in 33% yield. The earlier failure to add thiophene to benzyne generated by other methods must have been due to intervention of side reactions. Thiophyne also has been similarly trapped to yield benzo[A]thiophene (see Section 3.14.2.2). 

Halogen Derivatives of Thiophenes and Benzo[6]thiophenes 3.15.9.6.1 Fluorine derivatives... 

Carbonyl groups in polyfluorinated quinones assist the hydrolysis of fluorine. In tetrafluoro-1,4-benzoquinone (18). one or two of the fluorine atoms can thus be replaced by hydroxy groups, depending on the reaction conditions, to give 2,3,5-trifluoro-6-hydroxy-l,4-benzo-quinone (17) or 2.5-difluoro-3,6-dihydroxy-l,4-benzoquinone (19).24... 

Intramolecular replacement of fluorine by nitrogen has been used for the formation of fused heterocycles, i.e. derivatives of indole,187 - 189 2,3-dihydroindole.190 benzopyrazole.191 benzo-pyridazine,192 benzoxazine,193194 bcnzothiadiazole,193 quinoline,196-198 and benzothiazinc (e.g., 9).194 1"-200... 

Fluorination of benzo[6]thiophene in the vapor phase with cobalt trifluoride gives mainly perfluoroethylcyclohexane, formed by fission of the molecule, elimination of sulfur, and fluorination of the hydrocarbon fragment.480... 

The synthesis of fluotrimazole starts from m-xylene. Peroxide catalyzed perchlorination converts this to m-trichloromethyl-benzo-trichloride. m-Trichloromethyl-benzotrifluoride is then obtained by selective chlorine/fluorine exchange. This key product is also readily accessible on a technical scale by conproportionation of the two corresponding m-trihalomethyl-benzotrihalogenides. Friedel-Crafts reaction with benzene leads to trifluoromethyl-tritylchloride, which reacts smoothly with 1,2,4-triazole in polar solvents to give fluotrimazole. 

Fig. 2.20. Composition (mean%) of 16 individual polycyclic aromatic hydrocarbons (PAHs) to total PAHs detected in various environmental media in (a) air (n = 24), (b) soil (n = 226), (c) freshwater (n = 46), and (d) marine sediment (n = 159), from the South Korea. Naphthalene NAP, Acenaphthylene ACY, Acenaphthene ACE, Fluorine FLU, Phenanthrene PHE, Anthracene ANT, Fluoranthene FLT, Pyrene PYR, Benz[a]ant-hracene BaA, Chrysene CHR, Benzo[6]fluoranthene BbF, Benzo[ ]fluoranthene BkF, Benzo[a]pyrene BaP, Indeno[l,2,3,c,d]pyrene I123cdP, Dibenz[a,/z]anthracene DahA, Ben-zo[g,/y ]perylene BghiP.

NaNC>3 and cone. H2SC>4 gave 5-chloro I-nitrobenzo[2,l,3]selenadiazole 142 in 90% yield (Equation 7) <2004RJC428>. An improved method for nitration of fluorine-substituted benzo[2,l,3]selenadiazoles was also reported. Treatment of a variety of benzo[2,l,3]selenadiazoles with commercially available 90% nitric acid dissolved in a mixture of methanesulfonic acid and phosphorus pentoxide at room temperature gave 4-nitrobenzo[2,l,3]sclc-nadiazoles in 81-94% yield <2004JHC1023>. The obtained 2,1,3-benzoselenadiazoles were used as precursors to o-phenylenediamines (see Section 6.12.5.8). 

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