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A new method for the synthesis of 4-chlorononafluoro- and 4-bromononafluorobiphenyl by the reactions of nonafluorobiphenyl-4-thiol with Cl2, PCl5, and Br2, as well as of 4,4′-dichlorooctafluorobiphenyl from octafluorobiphenyl-4,4′-dithiol, 4′-chlorooctafluorobiphenyl-4-thiol, Cl2, and PCl5 was developed. 4-Bromo-4′-chlorooctafluorobiphenyl was synthesized for the first time from 4′-chlorooctafluorobiphenyl-4-thiol and Br2. 4,4′-Dichlorooctafluorobiphenyl was obtained as the main product in the reaction of 4′-bromooctafluorobiphenyl-4-thiol with PCl5.

A new method for the preparation of 2,3,4,5-tetrafluorophenol from 2-[(2,3,4,5,6-pentafluorophenyl)thio]acetic acid has been proposed. It included the intramolecular cyclization of the salt of this acid in the presence of K2CO3 with the substitution of the ortho fluorine atom and the formation of a lactone, which under the reaction conditions underwent the ring-opening with the formation of the potassium salt of 2-[6-hydroxy(2,3,4,5-tetrafluorophenyl)-thio]acetic acid. The resulting salt was converted into methyl ester and desulfurized with Raney nickel to 2,3,4,5-tetrafluorophenol. The proposed method is a simple and efficient way to obtain poorly available 2,3,4,5-tetrafluorophenol in ∼58% total yield based on 2-[(2,3,4,5,6-pentafluorophenyl)thio]acetic acid.

Pyrolysis of a mixture of 2,5-difluoro-3,4,6-trichlorobenzenethiol with tetrafluoroethylene leads to 2,2,3,3,4,7-hexafluoro-5,6-dichloro-2,3-dihydrobenzo[b]thiophene (the major reaction product) along with 2,2,3,3,4,6-hexafluoro-5,7-dichloro-2,3-dihydrobenzo[b]thiophene. Schemes of their formation with the participation of intermediate radicals are proposed. Oxidation of a mixture of the synthesized compounds gave 2,2,3,3,4,7-hexafluoro-5,6-dichloro-2,3-dihydrobenzo[b]sulfane-1,1-dioxide and 2,2,3,3,4,6-hexafluoro-5,7-dichloro-2,3-dihydrobenzo[b]sulfane-1,1-dioxide.

Dodecafluoro-2H,3H,5H,6H,7H-indeno[5,6-b]thiophene has been synthesized as the major product of co-pyrolysis of 6-bromo-, 6-chlorooctafluoroindane-5-thiols, or bis(6-bromo-5-perfluoroindanyl)disulfane with tetrafluoroethylene under flow conditions at 400-625oC, along with small amount of tetradecafluoro-1,2,3,5,6,7-hexahydro-s-indacene. Dodecafluoro-2H,3H,5H,6H,7H-indeno[5,6-b]thiophene formed in the reaction of 6-(meth-ylsulfanyl)octafluoroindane-5-thiol with tetrafluoroethylene at 420oC has been isolated, and its structure has been confirmed by X-ray diffraction analysis. The schemes of the products formation involving intermediate radicals have been proposed.

Co-pyrolysis of 2,5-dichloro-3,4,6-trifluorobenzenethiol, 2-chloro-4-trifluoromethyl-3,5,6-trifluorobenzenethiol, and 3-chloro-2,5,6-trifluoropyridine-4-thiol with tetrafluoroethylene has given, heptafluoro-5- chloro-2,3-dihydrobenzo[b]thiophene, 6-trifluoromethylheptafluoro-2,3-dihydrobenzo[b]thiophene, and heptafluoro- 2H,3H-thieno[2,3-c]pyridine, respectively, as the major products. The reactions of these thiols containing the chlorine atom in the ortho-position to the thiol group differ from that between 4-chloro-2,3,5,6- tetrafluorobenzenethiol and tetrafluoroethylene, the latter one giving perfluoroindane as the major product.

Replacement of the thiol group in polyfluoroarenethiols with chlorine was performed by treating with PCl5 as chlorinating agent. By heating in ampules at 200–220°C polyfluoro- and polyfluorochloroarenethiols with PCl5 mono- and dichloropolyfluoroarenes and also 1,2,4-trifluorotrichlorobenzene were synthesized. Dichloropolyfluoroarenes contain chlorine atoms in ortho- and para-positions.

1,2,4-Trichlorotrifluorobenzene reacted with potassium hydrogen sulfide, potassium hydroxide, sodium isopropoxide, liquid ammonia, and ethyl cyanoacetate via nucleophilic substitution of one fluorine atom with predominant formation of the isomer in which the new substituent replaced fluorine atom in the 5-position.

1,2-Dichlorotetrafluorobenzene was obtained by reactions of chlorine with 5,6,7,8-tetrafluoro-1,4-benzodioxane and with a mixture of 3,4,5,6-tetrafluorophthaloyl chloride and 3,3-dichloro-4,5,6,7-tetrafluorophthalide at 500–550°C. Pyrolysis of pure 3,4- and 2,5-dichlorotrifluorobenzenethiols, as well as of a mixture of 3,4-, 2,4-, and 2,5-dichlorotrifluorobenzenethiols, in the presence of chlorine at 400–415°C in a flow system gave difficultly accessible 1,2,4-trichlorotrifluorobenzene.

Joint pyrolysis with chlorine and bromine of polyfluoroarenethiols, -hetarenethiols, and their derivatives at 300–650°C furnished polyfluorocompounds containing chlorine and bromine.