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Crosslinked poly[styrene-co(4-vinylpyridinium dichloroiodate(1–))] can be used as a very efficient polymeric reagent for α-iodination of ketones, diketones, and corresponding enol acetates.

Halofluorination of norbornadiene with N-bromosuccinimide, N-chlorosuccinimide or xenon difluoride in the presence of polyhydrogen fluoride-pyridine resulted in the formation of three products: 3- endo -halo-5- exo -fluoro ( 2 ) and 3- exo -halo-5- exo -fluoronortricyclane ( 3 ), and 2- exo -fiuoro-7- syn -halo-norbornene-5 ( 4 ). The exo -attack of the electrophile on norbornadiene is slightly predominant (65% X = Br, 64% X = Cl, 73% X = F) over the endo -attack. The Meerwein-Wagner rearrangement occurred only in the case of chlorine or fluorine halosubstituents of β-carbonium ions formed by exo attack of the electrophile.

UV irradiation of 2-iodo-3,4-dihydro-1(2H)-naphthalenone and 2-iodo-1-indanone has been found to involve competing radical and ionic photoprocesses. The carbonyl group, phenyl ring and ring size of cycloketones have an influence on the nature of the photochemical carbon–iodine bond cleavage.

The fluorination of 9,10-dihydroanthracene and triptycene with xenon difluoride in the presence of hydrogen fluoride occurred at α and β position with β attack predominating over α attack, while the reaction with acenaphthene resulted in the formation of 2- and 4-fluorosubstituted products, regioselectivity being very little affected by the nature of the catalyst: hydrogen fluoride, boron trifluoride and pentafluorothiophenol. The fluorination of 1,2,3,4-tetrahydro-1,4-methanonaphthalene resulted in the formation of 6-fluoro-1,2,3,4-tetrahydro-1,4-methanonaphthalene, 6,7-difluoro-1,2,3,4-tetrahydro-1,4-methanonaphthalene and rearranged product 1-(2,2-difluoroethyl) indan.

Irradiation of a cyclohexane solution of pentafluoropyridine and 1-phenyl-2-alkylacetylenes produced regiospecific 2+2 photocycloaddition, thus forming 3-aza-bicyclo[4.2.0] octa-2,4,7-triene derivatives, which further phototransformed to 7-aza-tricyclo[4.2.0.0 2,5 ]octa-3,7-diene derivatives. Further phototransformation of the tricyclic system depended on the alkyl substituent: in the case of tert-butyl, 1,2,5,6,7-pentafluoro-3-tert-butyl-4-phenyl-8-aza-bicyclo[4.2.0]octa-2,4,7-triene was formed, while in the case of a methyl substituent, 1-methyl-2,3,5,6,7-pentafluoro-8-phenyl-4-aza-cycloocta- 1,3,5,7-tetraene resulted.

Bei der Fluorierung von l,2,4,5-Tetramethylbenzol (III) mit Xenondi- fluorid (II) spielt der zugesetzte Katalysator eine wesentliche Rolle, mit HF erhalt in Abhangigkeit von der Stochiometrie die Fluorverbindungen (I) bzw. (IV).

Bei der Umsetzung mit Xenondifluorid erhalt man aus den Phenyl-cycloalkenonen (I) die isomeren Fluorverbindungen (II) und (III).

The photochemistry of fluoro-substituted aromatic and heteroaromatic molecules is reviewed. Investigations in this field of organic fluorine chemistry are summarized and some recent observations are presented. It is concluded that the fluorine atom is a convenient substituent for the elucidation of the reaction pathways of photochemical transformations of aromatic and heteroaromatic molecules.

2 + 2 photoaddition of cyclopentene to hexafluorobenzene in cyclohexane solution proceeds predominately via anti(85%) rather than syn attack (15%).

The stereochemistry of photocycloaddition reactions of various cyclodienes to hexafluorobenzene in cyclohexane solution depends on the structure of the cyclodiene and [2+2]cycloadducts are mainly observed. Photoreaction of 1,5-cyclooctadiene with hexafluorobenzene gives nearly equal amounts of syn and anti[2+2]adducts, which are further transformed to tetracyclic systems, contrary to this, the stereochemistry observed by reactions with 1,4-cyclohexadiene depends on the molar ratio of cyclodiene–hexafluorobenzene and 30–54% of syn addition is observed, the syn adduct, however, being further transformed to 2,3,4,5,6,7-hexafluoropentacyclo[6.4.0.02,7.03,11.06,10]dodec-4-ene. Syn selectivity of [2+2]cycloaddition was enhanced when bicyclic dienes were used and it is interesting that in the case of norbornadiene and benzonorbornadiene only exo attack was observed, and no anti attack occurred in the case of benzonorbornene. The quantum yields of [2+2]photocycloaddition reactions depend on the structure of the c...

The fluorination of 9,10-dihydroanthracene and triptycene with xenon difluoride in the presence of hydrogen fluoride occurred at α and β position with β attack predominating over α attack, while the reaction with acenaphthene resulted in the formation of 2- and 4-fluorosubstituted products, regioselectivity being very little affected by the nature of the catalyst: hydrogen fluoride, boron trifluoride and pentafluorothiophenol. The fluorination of 1,2,3,4-tetrahydro-1,4-methanonaphthalene resulted in the formation of 6-fluoro-1,2,3,4-tetrahydro-1,4-methanonaphthalene, 6,7-difluoro-1,2,3,4-tetrahydro-1,4-methanonaphthalene and rearranged product 1-(2,2-difluoroethyl) indan.

A polymeric aryliodine(III) difluoride has been prepared and used to fluorinate several phenyl-sub-stituted olefins to their difluorides in high yields under mild conditions.

Halofluorination of 1,2-dihydronaphthalene with a mixture of N-chlorosuccinimide or N-bromosuccinimide or N-iodosuccinimide–hydrogen fluoride–pyridine in ether proceeds with Markovnikov type regioselectivity. The reaction is stereospecifically anti, the anti adduct isomerizing to syn products under the reaction conditions. The elimination of hydrogen halide under basic conditions occurs only from the syn adduct, thus forming 1-fluoro-3,4-dihydronaphthalene. Halofluorinations of 1,4-dihydronaphthalene also occur stereospecifically anti, and elimination under basic conditions gives naphthalene.

Xenon difluoride reacts with 1,1-diphenylethylenes in the presence of hydrogen fluoride or trifluoroacetic acid as catalyst to form the corresponding 1,2-difluoroacetic acid as catalyst to form the corresponding 1,2-difluoro-1,1-diphenylethanes in nearly quantitative yields.

The reaction of substituted (difluoroiodo)arenes with 1-phenyl-1-(m-chlorophenyl)ethylene results in 1,1-difluoro-1-(m-chlorophenyl)2-phenylethane, with 1-phenyl-1-(p-methoxyphenyl)ethylene in 1,1-difluoro-1-phenyl-2-(p-methoxyphenyl) ethane, and with 1-phenylcyclopentene and 1-phenylcyclohexene in rearranged gem-difluoro compounds. The reaction with norbornene results in three products: fluoronortricyclane (9–12%), 2-exo-7-syn-difluoronorbornane (75–86%), and 2-exo-7-anti-difluoronorbornane (5–15%) depending upon the substituent on the phenyl ring in (difluoroiodo)arenes.

Fluorination of 1,3-diketones with xenon difluoride in the presence of the insoluble cross-linked polystyrene–4-vinylpyridine complex with boron trifluoride and insoluble cross-linked polystyrene–4-vinyl-pyridine resins resulted in the formation of mono- and di-fluoro products, while reactions with enol acetates in the presence of hydrogen fluoride gave α-fluoroketones.

Photoaddition of indene or 1,2-dihydronaphthalene to hexafluorobenzene in cyclohexane solution results in the formation of cis-syn-cis-2 + 2-cycloadducts.

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2 + 2 photoaddition of cyclopentene to hexafluorobenzene in cyclohexane solution proceeds predominately via anti(85%) rather than syn attack (15%).

Xenon difluoride readily reacts with various organo-sulphur compounds. In general, three types of products were isolated, the course of the reactions depending on the structure of the organo-sulphur substrate. Alkyl-phenyl substituted sulphides, 3,3-dibromothiochroman-4-one and thiochroman-4-ol reacted to form α-fluoro substituted products, 2,5-diphenyltetrahydrothiopyran-4-one, thiochroman-4-one and 3-bromothiochroman-4-one formed dehydrogenated products, while diphenyl-sulphide, dibenzothiophene and 10-thioxanthenone reacted to form sulphoxide and sulphone. The reaction mechanism and the reaction pathways, which are shown on the Scheme, will be discussed.

Caesium fluoroxysulphate in acetonitrile medium at 35°C converts primary alcohols and alkyl, as well as aryl aldehydes, to acid fluorides in high yield.

Leong and Peach (J. Fluorine Chem., 6, 145 (1975) have shown that at room temperature pentafluorothiophenol readily reacted with 1-hexene and phenylacetylene forming adducts, the reactions following anti-Markovnik type regio-selectivity, and suggested a free radical mechanism.