Patent GB-661375-A (GB)
Title: A process for the preparation of cyclic thioethers
Filed: 1948-04-07
Abstract: Thioxanes having the general formula <FORM:0661375/IV (a)/1> in which R1 to R8 inclusive each represents a hydrogen or halogen atom or an alkyl radical containing not more than 5 carbon atoms are prepared by subjecting a polymeric material of the group consisting of poly-(di-2-hydroxyalkyl) - sulphides, formaldehyde poly - (di - 2-alkyl)-sulphides obtainable by heating di-2-hydroxyalkyl sulphides with diethylformal, and hydrogen sulphide-di-2-alkenyl ether adducts, which have recurring structural units of the general formula <FORM:0661375/IV (a)/2> wherein R1 to R8 are as defined above, n is an integer greater than 1 and x is zero or one, to a temperature of from 150 DEG  to 500 DEG  C. under a pressure sufficient to maintain the said polymeric material in the solid or liquid state.  The products include minor amounts of the corresponding 1 :4-dithianes. The process is one of simple heat treatment which may be carried out in the presence or absence of acidic materials as catalysts, e.g. inorganic or sulphonic acids, and inert diluents or solvents, e.g. aromatic, alicyclic, saturated acyclic or aliphatic-aromatic hydrocarbons and in batchwise or continuous operation.  The preferred temperature is one slightly above the boiling temperature of the selected polymeric material.  Atmospheric, or higher or lower pressure may be used.  Suitable apparatus for use with liquid polymers comprises heated tubular reactors containing inert substances to restrict the flow of the liquid reactants. Preferred polymeric starting materials are those obtained by polymerization of one or more 2 : 21-dihydroxy dialkyl sulphides, especially those having the formula <FORM:0661375/IV (a)/3> wherein the R's represent a hydrogen atom or an alkyl radical having not more than 5 carbon atoms, by heating in the presence of a dehydration promoting catalyst, and those obtained by the photochemical addition of hydrogen sulphide to di-2-alkenyl oxyethers of the formula <FORM:0661375/IV (a)/4> where R1 and R2 are also hydrogen atoms or alkyl radicals having not more than 5 carbon atoms.  In examples: (1) a polymer of bis-(2-hydroxyethyl)-sulphide, M.W.600, is heated under atmospheric pressure at 200 DEG  C., yielding a distillate of B.P. 140-160 DEG  C. being substantially 1 : 4-thioxane with some 1 : 4-dithiane; (2) equimolar amounts of divinyl ether and liquefied hydrogen sulphide are sealed in an evacuated quartz bomb in ice and irradiated by ultra-violet light yielding, after stripping off volatiles, a greasy product having a molecular weight of 1000 to 1100 which is heated at 200 DEG  C. under atmospheric pressure to form 1 : 4-thioxane and a minor amount of 1 : 4-dithiane; (3) a similar product is obtained by decomposing, under the same conditions, formaldehyde poly 2 : 21-dihydroxy diethyl sulphide (M.W.825) prepared by refluxing equimolar amounts of ethylal and 2 : 21-dihydroxy diethyl sulphide in benzene in presence of a small amount of p-toluene sulphonic acid, and azeotropically distilling the product with benzene until the temperature of the residue rises to 140 DEG  C. whereupon the residue is dissolved in benzene, washed with aqueous sodium carbonate and dried; (4) poly bis-(2-hydroxy isopropyl) sulphide of M.W. about 900 is heated under atmospheric pressure at 225 DEG  C. yielding mainly 3 : 5-dimethyl-1 : 4-thioxane; (5) equimolecular amounts of di-isopropenyl ether and hydrogen sulphide are reacted under the influence of ultra-violet light and the resulting polymer of approximate M.W.900 is decomposed under atmospheric pressure at about 225 DEG  C. to form mainly 2 : 6 - dimethyl - 1 : 4 - thioxane; (6) ethylal and 2 : 2-dihydroxy diisopropyl sulphide are reacted in equimolar amounts in presence of p-toluene sulphonic acid in an inert solvent and the resulting polymer of approximate M.W.1100 is heated as in (5) to yield mainly 3 : 5-dimethyl-1 : 4-thioxane and formaldehyde.  Many other 1 : 4-thioxanes are mentioned as examples of products also obtainable by the process.  In addition, further examples of the polymeric starting materials are given, typical of these being poly 2-hydroxy-ethyl 2-hydroxy isopropyl sulphide, poly bis-(1 - methylol butyl) - sulphide, poly bis - (1-methylolpentyl)-sulphide, poly bis-(1-chloro-2-hydroxyethyl)-sulphide and formaldehyde poly 1-methylolpropyl 2-hydroxyethyl sulphide.  The thioxanes may be used as reaction media for reactions employing strong acids at elevated temperatures.  The Specification as open to inspection under Sect. 91 relates to the production of 1 : 4-thioxanes by heat treatment of any polymeric substance containing the above-mentioned structural unit. This subject-matter does not appear in the Specification as accepted.ALSO:Thioxanes having the general formula <FORM:0661375/IV (b)/1> in which R1 to R8 inclusive each represents a hydrogen or halogen atom or an alkyl radical having not more than 5 carbon atoms are prepared by subjecting a polymeric material of the group consisting of poly-(di-2-hydroxyalkyl sulphides), formaldehyde poly-(di-2-hydroxy-alkyl) sulphides obtained by heating di-2-hydroxyalkyl sulphides with diethyl formal, and hydrogen sulphide-di-2-alkenyl ether adducts, having recurring structural units of the general formula <FORM:0661375/IV (b)/2> wherein R1 to R8 are as defined above, n is an integer greater than one and x is zero or one, to a temperature of from 150 DEG  to 500 DEG  C. under a pressure sufficient to maintain the said polymeric material in liquid or solid state.  The products include minor amounts of the corresponding 1 : 4-dithianes.  The heating may be carried out in the presence or absence of acidic materials as catalysts, e.g. mineral acids or sulphonic acids, and inert diluents or solvents, e.g. aromatic, alicyclic, saturated acyclic or aliphatic aromatic hydrocarbons, and in batch-wise or continuous operation.  The preferred temperature is one slightly above the boiling temperature of the selected polymeric material. Atmospheric or higher or lower pressure may be used.  Suitable apparatus for use with liquid starting materials comprises heated tubular reactors containing inert substances to restrict liquid flow.  Preferred polymeric starting materials are those obtained by polymerization of one or more 2 : 21-dihydroxy dialkyl sulphides, especially those of the general formula <FORM:0661375/IV (b)/3> wherein the R's represent hydrogen or alkyl radicals having not more than 5 carbon atoms, by heating in presence of a dehydration-promoting catalyst, and those obtained by photo-chemical addition of hydrogen sulphide to di-2-alkenyl oxyethers of the general formula <FORM:0661375/IV (b)/4> wherein the R's are hydrogen or alkyl radicals having not more than 5 carbon atoms.  In examples: (1) a polymer of bis-(2-hydroxyethyl) sulphide of M.W. 600 is heated under atmospheric pressure at 200 DEG  C., yielding a distillate which is mainly 1 : 4-thioxane and some 1 : 4-dithiane; (2) divinyl ether and liquefied hydrogen sulphide in equimolar amounts are sealed in an evacuated quartz bomb in ice and irradiated by ultra-violet light yielding after stripping off volatiles, a greasy solid of M.W. 1000-1100 which is heated under atmospheric pressure at 200 DEG  C. to yield mainly 1 : 4-thioxane and some 1 : 4-dithiane; (3) a similar mixed product is obtained by decomposing under the same conditions, formaldehyde poly - 2 : 21 - dihydroxy diethyl sulphide (M.W. 825) prepared by refluxing equimolar amounts of ethylal and 2 : 21-dihydroxy diethyl sulphide in benzene in presence of a small amount of p-toluene sulphonic acid, azeotropically distilling the product with benzene until the temperature of the residue reaches 140 DEG  C., dissolving the residue in benzene, washing with aqueous sodium carbonate and drying; (4) poly bis-(2-hydroxyisopropyl) sulphide of approximate M.W. 900 is heated under atmospheric pressure at 225 DEG  C. yielding mainly 3 : 5-dimethyl-1 : 4-thioxane; (5) di-isopropenyl sulphide and hydrogen sulphide are interacted in equimolar amounts under the influence of ultra-violet light and the resulting polymer of approximate M.W. 900 is heated under atmospheric pressure at about 225 DEG  C. to yield mainly 2 : 6-dimethyl-1 : 4-thioxane; (6) 2 : 21-dihydroxy diisopropyl sulphide and ethylol are reacted in equimolar amounts in presence of p-toluene sulphonic acid and an inert solvent and the resulting polymer of approximate M.W. 1100 is heated as in (5) to yield mainly 3 : 5-dimethyl-1 : 4-thioxane and formaldehyde.  Many other 1 : 4-thioxanes are mentioned as examples of products also obtainable by the process of the invention.  In addition, further examples of the polymeric starting materials are given, typical of these being poly-2-hydroxyethyl-2-hydroxyisopropyl sulphide, poly-bis-(1-methylol butyl) sulphide, poly-bis-(1-methylol pentyl) sulphide, poly-bis-(1-chloro-2-hydroxyethyl) sulphide and formaldehyde poly - 1 - methylolpropyl - 2 - hydroxyethyl sulphide. The thioxanes may be used as reaction media for reactions employing strong acids at elevated temperatures.  The Specification as open to inspection under Sect. 91 relates to the production of 1 : 4-thioxanes by heat treatment of any polymeric substance containing the above-mentioned structural unit and refers to the use of the thioxanes as reaction media in sulphonation reactions.  This subject-matter does not appear in the Specification as accepted.