V. R. Sinyakov

Pentafluorophenylation of perfluorinated benzocyclobutene, indan, and tetralin by reaction with pentafluorobenzene in SbF5

The reactivity of perfluorinated benzocyclobutene, indan, and tetralin in reaction with pentafluorobenzene in SbF5 medium, and also the relative stability of generated therewith perfluoro-1-phenylbenzocycloalkenyl cations decrease with increasing alicyclic fragment in the benzocycloalkene. Treating the solutions of salts of the above cations with anhydrous HF results in the corresponding perfluoro-1-phenylbenzocycloalkenes, and the hydrolysis of salts furnishes their 1-hydroxy derivatives. In a reaction of 1-hydroxyperfluoro-1-phenylbenzocyclobutene, -indan, and -tetralin with SOCl2 the hydroxy group is replaced by chlorine. Besides with indan and tetralin derivatives form respectively 7-pentafluorophenyloctafluoro-3-chlorobicyclo[4.3.0]hepta-1,4,6-triene and 7-pentafluorophenyldecafluoro-3-chlorobicyclo[4.4.0]octa-1,4,6-triene.

Reaction of perfluorinated 1-ethyl-, 1,1-diethyl-, and 1,2-diethylcyclobutabenzenes with pentafluorobenzene in SbF5

Perfluoro(1-ethyl-1,2-dihydrocyclobutabenzene) reacts with pentafluorobenzene in SbF5 to give perfluoro(1-ethyl-2-phenyl-1,2-dihydrocyclobutabenzene). Analogous reaction of a mixture of perfluoro(1,1-diethyl-1,2-dihydrocyclobutabenzene) and perfluoro(1,2-diethyl-1,2-dihydrocyclobutabenzene) leads to the formation (after hydrolysis of the reaction mixture) of perfluorinated 7-phenyl-8,8-diethylbicyclo[4.2.0]octa-1,4,6-trien-3-one, 1,1-diethyl-2-(4-oxocyclohexa-2,5-dienylidene)-1,2-dihydrocyclobutabenzene, and 2-(pent-2-en-3-yl)benzophenone (from the 1,1-isomer) and perfluorinated (E)-1,2-diethyl-1-phenyl-1,2-dihydrocyclobutabenzene, 7,8-diethyl-8-phenylbicyclo[4.2.0]octa-1,4,6-trien-3-one, and 1-[2-(1-phenylprop-1-en-1-yl)-phenyl]propan-1-one (from the 1,2-isomer).

Reactions of Perfluorobenzocycloalkenes with Ethyl Cyanoacetate and Methyllithium and Some Transformations of the Products

Reactions of perfluorobenzocycloalkenes (ArFF) with methyllithium and ethyl cyanoacetate involved replacement of fluorine atoms in positions 3 and 4 of perfluorocyclobutabenzene, position 5 of perfluoroindan, and position 6 of perfluorotetralin by CH3 and CH(CN)COOEt groups. Hydrolysis of the resulting esters ArFCH(CN)COOEt gave the corresponding perfluoroarylacetic acids ArFCH2COOH which were converted into dichloroacetyl chlorides ArFCCl2COCl by treatment with PCl5. The reaction of ArFCCl2COCl with SbF5 produced trifluoromethyl derivatives ArFCF3. Decarboxylation of ArFCCl2COOH in DMF afforded dichloromethyl derivatives ArFCCl2H which reacted with CsF on heating to form difluoromethyl analogs ArFCF2H.

Skeletal transformations of pentafluorophenylation products of perfluorinated 1,2-dialkyl-1,2-dihydrocyclobutabenzenes in SbF5

Perfluorinated 1-ethyl-2-methyl- and 1-isopropyl-2-methyl-1,2-dihydrocyclobutabenzenes reacted with pentafluorobenzene in SbF5 to generate perfluoro(1-ethyl-2-methyl-2-phenyl- and perfluoro(1-izopropyl-2-methyl-2-phenyl-1,2-dihydrocyclobutabenzen-1-yl) cations. These cations in SbF5 at 20°C underwent opening of the four-membered ring and its expansion to five-membered. After hydrolysis, perfluorinated 4-[1-(2-propylphenyl)ethylidene]- and 4-[1-(2-isobutylphenyl)ethylidene]-2,5-cyclohexadien-1-ones were obtained together with perfluoro(3-ethyl- and perfluoro(3-isopropyl-2-phenylinden-1-ones).

Reactions of perfluorinated 1-ethyltetrahydronaphthalene, 1-ethylindan, and 1,1-diethylindan with pentafluorobenzene in antimony pentafluoride

The reaction of perfluoro(1-ethyltetrahydronaphthalene) with pentafluorobenzene in SbF5, followed by treatment of the reaction mixture with water, afforded a mixture of 1-hydroxyperfluoro(1-phenyl-4-ethyletetrahydronaphthalene) and perfluoro(5-phenyl-8-ethyl-2,6,7,8-tetrahydronaphthalen-2-one). From perfluoro(1,1-diethylindan), 1-hydroxyperfluoro(1,1-diethyl-3-phenylindan) was obtained. Perfluoro(1-ethylindan) reacted with an equimolar amount of pentafluorobenzene in SbF5 to give (after hydrolysis) 1-hydroxyperfluoro-(3-ethyl-1-phenylindan), 1-hydroxyperfluoro(3-ethyl-1,3-diphenylindan), and perfluoro(1-ethyl-1-phenylindan), while in the reaction with excess pentafluorobenzene, followed by treatment with anhydrous hydrogen fluoride, perfluoro(1-ethyl-3-phenylindan) and perfluoro(1-ethyl-1,3-diphenylindan) were formed.

Expansion of the pentafluorobenzene ring and other skeletal transformations in the reaction of perfluoro(1,2-diethyl-1-phenyl-1,2-dihydrocyclobutabenzene) with antimony pentafluoride

The reaction of perfluoro(1-phenyl-1,2-diethyl-1,2-dihydrocuclobutabenzene) with SbF5 at 20°C, followed by treatment of the reaction mixture with water gave perfluoro {4-[1-(2-propylphenyl)propylidene]-2,5-cyclohexadien-1-one} together with perfluoro[4b,10-diethylbenzo[a]azulen-7(4bH)-one] resulting from unusual expansion of the pentafluorobenzene ring to seven-membered ring. Analogous reaction at 90°C, apart from the above compounds, afforded perfluorinated 10-ethyl- and 3,10-diethylbenzo[a]azulen-6(10H)-ones via elimination of C2F5 group from the seven-membered ring or its migration to the benzene ring.

Chlorination and decarboxylation of (heptafluoronaphthalen-2-yl)acetic acid. Synthesis of 2-(dichloromethyl)- and 2-(difluoromethyl)heptafluoronaphthalenes

Decarboxylation of (heptafluoronaphthalen-2-yl)acetic acid in DMF in the presence of NaHCO3 gave 2-methylheptafluoronaphthalene, and treatment with PCl5 on heating afforded dichloro(heptafluoronaphthalen-2-yl)acetic acid. Decarboxylation of the latter in DMF led to the formation of 2-(dichloromethyl)-heptafluoronaphthalene which was converted to 2-(difluoromethyl)heptafluoronaphthalene by heating with cesium fluoride.

Reaction of Perfluorobenzocyclobutene with Excess Pentafluorobenzene in SbF 5

The reaction of perfluorobenzocyclobutene with excess pentafluorobenzene in SbF5, followed by hydrolysis, gave a mixture of perfluoro-1,3,3-triphenyl-1,3-dihydro-2-benzofuran-1-ol, perfluoro-1,1,2-triphenylbenzocyclobuten- 5-one, and perfluoro-4-(2,2-diphenylbenzocyclobuten-1-ylidene)cyclohexa-2,5-dien-1- one. When the reaction mixture was treated for a long time with Olah’s reagent (HF–pyridine), isomeric perfluoro-9,10-diphenyl-1,4-, -1,10-, -2,9-, and -9,10-dihydroanthracenes were formed and were converted to perfluoro-9,10-diphenylanthracene by the action of SbF5.

Synthesis of (6,7-dichlorononafluoro-5,6,7,8-tetrahydronaphthalen-2-yl)acetic acid and its transformation into perfluorinated 2-methylnaphthalene and 6-methyl-1,4-dihydronaphthalene

Abstract2,3-Dichlorodecafluorotetralin reacted with ethyl cyanoacetate to give ethyl 2-cyano-2-(6,7-dichlorononafluoro-5,6,7,8-tetrahydronaphthalen-2-yl)acetate which was hydrolyzed to (6,7-dichlorononafluoro-5,6,7,8-tetrahydronaphthalen-2-yl)acetic acid. The latter was treated with PCl5 on heating to obtain 2,2-dichloro-(6,7-dichlorononafluoro-5,6,7,8-tetrahydronaphthalen-2-yl)acetyl chloride which was converted to 2,3-dichlorononafluoro-6-trifluoromethyl-1,2,3,4-tetrahydronaphthalene by the action of SbF5. The reduction of 2,3-dichlorononafluoro-6-trifluoromethyl-1,2,3,4-tetrahydronaphthalene with zinc in 1,4-dioxane gave perfluoro-6-methyl-1,4-dihydronaphthalene, and in DMF, perfluoro-2-methylnaphthalene.