925. Aromatic polyfluoro-compounds. Part VI. Penta- and 2,3,5,6-tetra-fluorothiophenol

Abstract

Pentafluorothiophenol and 2,3 , 5,6-tetrafluorothiophenol have been prepared by reaction of sodium hydrogen sulphide in pyridine with hexaand penta-fluorobenzene, respectively. Characterisation was effected by desulphurisation with Raney nickel. The products formed disulphides and methyl ethers. The ultraviolet and infrared absorption spectra of the compounds prepared are reported and the effects of the strongly electron-withdrawing groups briefly considered.THE susceptibility of hexa-and penta-fluorobenzene to attack by nucleophilic reagents has now been well e~tablished,l-~ for ethers, amines, and hydrazines have been prepared. Pyridine has been used3 as a solvent in which to prepare pentafluorophenol from hexafluorobenzene and potassium hydroxide; it had been employed earlier in syntheses of derivatives such as pentachlorothiophenol from hexachlorobenzene. We now report its use in the preparation of fluorothiophenols. Both hexa-and penta-fluorobenzene reacted vigorously with sodium hydrogen sulphide in pyridine-ethylene glycol to give good yields of penta-and tetra-fluorothiophenol, respectively.It has been suggested that pyridine acts in a catalytic capacity in reactions of hexachlorobenzene with nucleophiles. A similar effect on the reaction rate was noticed with substituted pyridines such as the picolines and lutidines. A notable exception, however, was 2,6-lutidine which, although a good solvent for the system, did not effect the same increase in reaction rate; this was attributed to the blocking of the hetero-nitrogen atom by the two o-methyl groups. Presumably the action of the pyridine is to increase the electron density around the halogen atom that is to be eliminated, and thus to assist it to escape as an ion from the aromatic nucleus.The possibility that a penta-or tetra-fluorophenylpyridinium fluoride might be formed as an intermediate was considered. A solution of hexafluorobenzene in pyridine rapidly darkened and, after 10-15 hr. a t 15", removal of all volatile material left a dark solid which appeared from a preliminary examination to be polymeric (cf. the reaction of pyridine with octafluorocyclobutene '). However, under the time and temperature conditions of the reaction producing pentafluorothiophenol a good recovery of the components of the mixture (hexafluorobenzene and pyridine) was made by gas-chromatographic techniques.Both fluoro-thiols were obtained as pungent liquids with strongly acidic properties, the potassium salts being easily recrystallized from water. It was of interest that crystalline potassium pentafluorothiophenoxide monohydrate became blue on storage ; this is perhaps a consequence of the presence of thiocarbonyl groups arising from electron migrations in the crystal lattice. The absence of such a blue colour in crystals of potassium 2,3,5,6-tetrafluorothiophenoxide is significant, the necessary migrations being less easy with hydrogen in the +ara-position.Cleavage of the carbon-sulphur linkages of each of the thiols was easily effected with Raney nickel, the corresponding...

Fluorinated 1,3λ4δ2,2,4‐Benzodithiadiazines − A Synthetic, Structural and Theoretical Study

“…Compounds 3Ϫ5 were obtained as black crystals. [25] 2,2Ј,3,3Ј,5,5Ј,6,6Ј-octafluorodiphenyl disulfide (21) [38] and 2,3,5,6-tetrafluoroaniline (23). [39] Starting Compound 17: The residue was distilled under vacuum, yielding, according to GC-MS and 19 F NMR, 0.35 g of a 2:1:6 mixture of 4,6,7-trifluoro-5-trifluoromethyl-2,1,3-benzothiadiazole (20), [25] 4,4Ј-bis(trifluoromethyl)-2,2Ј,3,3Ј,5,5Ј,6,6Ј-octafluorodiphenyl disulfide (22), [40] and 2,3,5,6-tetrafluoro-4-(trifluoromethyl)-aniline (24).…”

Some reactions of pentafluorothiophenol. Preparation of some pentafluoro-phenylthio metal derivatives

“…Bis(pentafluoro-pheny1thio)diphenyl lead decomposed at room temperature according to the equation A similar decomposition has been observed for bis(pheny1thio)diphenyl lead (22). Pentafluorothiophenol is readily oxidized, as are most thiols (2), to bis(pentafluor0-pheny1)-disulfide; bromine has been used as an oxidant (4). Reduction of the ions Cu2+, AuC14-, and PtClb2-and the compounds PbO, and H,TeO, has resulted in the formation of pentafluorophenylthio derivatives of Cu(I), Au(I), Pt(II), Pb(II), and metallic tellurium respectively.…”

“…In alkaline solution some polymerization of pentafluorothiophenol was observed forming perfluoropoly(pheny1ene sulfide), which can also be prepared by the reaction of sodium hydrogen sulfide with hexafluorobenzene in pyridine or by decomposition of pentafluoro-phenylthio potassium at 300" (4). The mechanism postulated is the nucleophilic attack by the pentafluorothiophenolate ion on other C6F5 nuclei, probably in the ortho and meta positions (4).…”

“…M(SC6F5), 2-, where M = Co(II), Pd(II), Pt(II), Zn, Cd, Hg(I1) (3); M(SC6F5), -, where M = Cu(I), Ag(I), Au(1) (3) ; Ag(SC6F5) (3); Pd(SC6F5), (3); and K(SC6F5). I .5H20 (4). The compound Cu(SC6F5) has been prepared from cuprous oxide and pentafluorothiophenol in ethanol ; no details of its physical properties are given, although it has been utilized to prepare bis(pentafluoropheny1) sulfide by its reaction with bromopentafluorobenzene in dimethyl formamide (5).…”

Preparation of some organotin compounds containing methylthio, phenylthio, and pentafluoro-phenylthio groups

“…The transient red color observed in the titration of thiopt~enol derivatives I T I U S~ be due to the forn~ation of unstable benzenesulfenyl iodide, PhSI. Hexafluorobenzene is susceptible to nucleophilic attack: pentafluorotl~iophenol is prepared from hexafluorobenzene and sodium bisulfide (8). The sulfiir in a sulfiir-tin bond can act as a nucleophile, forming a sulfonium compound; (methy1thio)-trimethyltin reacts with methyl iodide to form diinethyl(trimethylstannyl)sulfonium iodide (1).…”