Patent GB-577013-A (GB)
Title: Improvements in and relating to the manufacture of thiophenols
Filed: 1941-09-01
Abstract: Thiophenols are prepared by reducing at a temperature between 75 DEG and 300 DEG  C. aryl sulphides with hydrogen in the presence of a sulphactive hydrogenation catalyst, comprising the subsulphides, sulphides and polysulphides of the heavy metals of Groups I, IV, VI, VII and VIII of the Periodic Classification.  The preferred catalysts are the metal sulphide catalysts.  Metals mentioned include iron, nickel, cobalt, copper, silver, lead, chromium, molybdenum, palladium, tungsten, or combinations of the sulphides of these metals such as cobalt-nickel sulphide, cobalt-molybdenum sulphide, chromium-molybdenum sulphide and tungsten-molybdenum sulphide.  The sulphides are preferably prepared either by precipitation or by treating the metals or metal compounds with volatile sulphiding agents such as sulphur, hydrogen sulphide or carbon bisulphide.  The catalyst may be used in the pure state or supported on a carrier such as kieselguhr, alumina and silica gel. The reduction reaction is preferably carried out in solution in organic liquids such as hydrocarbons, alcohols and ethers.  The preferred reducing agent is hydrogen in the pure state, but mixtures of hydrogen with nitrogen, carbon monoxide, hydrocarbons and hydrogen sulphide may also be used. The compounds which may be treated by the process of the present invention includes sulphides derived from mononuclear aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, cumene, cymene and in general alkyl or alkenyl benzenes, also sulphides from polynuclear hydrocarbons such as the sulphides of biphenyl, triphenyl, fluorene, indene, naphthalene, anthracene, phenanthrene, acenaphthene, acenaphthylene, tetralin, naphthacene, pyrene, triphenylene, chrysene and picene.  In addition, mixed aryl-alkyl sulphides may also be used.  Compounds of several different types of sulphur linkages which are included in the general formula Ar-Sn-Ar1 may also be used.  Types mentioned are of the general formula <FORM:0577013/IV/1> and Ar-S-S-Ar.  Of the latter type tri- and polysulphides are also included.  The aryl nuclei may be substituted and for this there are mentioned as substituent groups hydroxyl, amino, chloro, bromo, iodo, nitro, nitroso, carboxyl, sulphonyl, sulphone chloride and saturated or unsaturated hydrocarbon groups. In examples: (1) Diphenyl sulphide is reduced in dioxane solution in the presence of a cobalt sulphide catalyst.  (2) A crude mixture of the mono-, di- and polysulphides of xylene obtained by the reaction of xylene with sulphur chloride in the presence of zinc chloride, is reduced in the presence of a cobalt sulphide catalyst.  (3) A solution of crude toluene sulphides in toluene is reduced in the presence of a precipitated nickel polysulphide catalyst.  (4) Naphthalene sulphides prepared by the reaction of naphthalene with sulphur chloride in the presence of zinc chloride are reduced in benzene solution in the presence of molybdenum sulphide catalyst. Other catalysts which may be used include cobalt, nickel and iron catalysts.  (5) A mixture of crude sulphides of biphenyl are reduced in an autoclave in the presence of iron mixed with sufficient sulphur to convert the iron into iron disulphide.  (6) A mixture of crude anthracene sulphides is reduced in benzene solution in presence of a cobalt sulphide catalyst.  (7) Crude cresol sulphides obtained by the action of sulphur chloride on cresol are reduced in benzene solution in the presence of a cobalt sulphide catalyst.  (8) A solid polymeric naphthyl monosulphide resin is reduced in benzene solution in the presence of a precipitated cobalt polysulphide catalyst to give a pale yellow oil consisting of a mixture of low molecular weight naphthyl sulphides and thionaphthols.  (9) p-p1-Dinitrodiphenyldisulphide is reduced in dioxane solution in the presence of a precipitated cobalt sulphide catalyst, to give after fractional distillation pure para-aminothiophenol.