GB1575853A

GB1575853A - Process for the manufacture and separation of substituted thianthrenes

Info

Publication number: GB1575853A
Application number: GB3531077A
Authority: GB
Original assignee: Hooker Chemicals and Plastics Corp
Current assignee: Occidental Chemical Corp
Priority date: 1976-11-01
Filing date: 1977-08-23
Publication date: 1980-10-01
Also published as: CA1064947A; IT1087969B; DE2739217A1; NL7710640A; BR7705620A; FR2369277B1; JPS5356673A; BE860090A; FR2369277A1

Description

(54) PROCESS FOR THE MANUFACTURE AND SEPARATION OF SUBSTITUTED THIANTHRENES (71) We, HOOKER CHEMICALS & PLASTICS CORP, a Corporation organised and existing under the laws of the State of New York, United States of America, of Niagara Falls, State of New York, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an improved process for the manufacture of substituted thianthrene compounds. Thianthrene and substituted thianthrenes are useful in a variety of chemical processes, for example, as chemical intermediates in the preparation of dyestuffs such as thianthrene vat dyes. In addition, various thianthrene compounds are useful plasticizers, pesticides, and flameproofing agents. Recently it has been found that substituted thianthrenes having electron withdrawing substituents, such as halogens, on the aromatic nuclei thereof are especially useful as components of catalyst systems for the directed nuclear chlorination of alkyl-benzenes. Although substituted thianthrenes have been known for many years, little effort has been directed toward the development of a process suitable for commercial manufacture.

In Specification No. 1456950 we describe and claim a method for the preparation of thianthrene which comprises the reaction of benzene with sulfur monochloride in the presence of aluminium chloride. The reaction product is a thianthrene aluminum chloride complex. The thianthrene may then be recovered from the complex by mixing the complex with an inert organic liquid to form a slurry, and treating the slurry with a Lewis base to free the thianthrene from said complex and to dissolve the thianthrene in the organic liquid. By this method thianthrene of high purity can be manufactured.

The present invention provides a process for separating a substituted thianthrene of the formula

wherein each X independently represents hydrogen, methyl, ethyl, chlorine, bromine or fluorine, subject to the proviso that not all X's on each benzene ring are hydrogen from a complex thereof with aluminum chloride, which process comprises mixing the complex with an organic liquid which is a solvent for the substituted thianthrene but not for the complex or for aluminum chloride to form a slurry of the complex, and treating the slurry with a Lewis base to which the organic liquid is inert to free the substituted thianthrene from the complex and to allow the substituted thianthrene to dissolve in the organic liquid.

The complex may be prepared as follows: Sulfur monochloride is added, preferably with stirring, to a stoichiometric excess of a substituted benzene compound of the formula

wherein each X independently represents hydrogen, methyl, ethyl, chlorine, bromine or fluorine, subject to the proviso that not all X's are hydrogen in the presence of aluminum chloride, and reacted to form the complex. In this process, it is preferred that sulfur monochloride be added to the substituted benzene compound rather than the reverse, since the addition of the substituted benzene compound to sulfur monochloride may result in the formation of undesirable polymeric sulfur products. Furthermore, the addition of the sulfur monochloride is made slowly to prevent excessively brisk evolution of hydrogen chloride gas. To provide a reaction medium of suitable consistency for agitation and transfer through piping systems and to provide sufficient solvent for by-product sulfur, substituted diphenyl sulfides and reaction impurities it is important that a molar ratio of substituted benzene compound to sulfur monochloride be maintained at about 5.0 or higher. Higher ratios may be employed with no theoretical upper limit. However, the process of the present invention becomes somewhat less economical when the mole ratio of substituted compound to sulfur monochloride is greater than about 12.0 due to the necessity of handling excessively large volumes of liquid. The preferred mole ratio of substituted benzene compound to sulfur monochloride is between 6:1 and 8:1.

The thianthrene compounds prepared in accordance with this invention are described hereinbelow in accordance with the current Chemical Abstracts system whereby the numbering of ring positions is as follows:

The amount of aluminum chloride present may vary considerably. However, we have found that maximum yields of the substituted thianthrene and minimum production of by-product substituted diphenyl sulfide are achieved when aluminum chloride is present in a mole ratio of aluminum chloride; sulfur monochloride of between 0.4:1 and 1.6:1. At lower ratios the yield of the substituted thianthrene is substantially lowered. At higher ratios, the yield of the substituted thianthrene is lowered and the production of substituted diphenyl sulfide is increased. The temperature of the reaction may vary considerably, for example, from about 20 Celsius to the boiling point of the substituted benzene compound.

Preferably, the reaction temperature is maintained at 60 to 1600 Celsius. At lower temperatures, increased formation of undesirable substituted diphenyl sulfides is likely to occur. The process is preferably carried out at atmospheric pressure, although subatmospheric and superatmospheric conditions may be employed, if desired, with appropriate adjustments in the upper temperature limit.

Upon completion of the reaction, the reaction vessel is cooled to room temperature and the contents filtered. The filtrate, consiting of substituted benzene compound and unwanted reaction by-products and impurities is removed and the remaining solids, a substituted thianthrene aluminum chloride complex, are slurried in the inert organic liquid, such a monochlorotoluene or benzene. A Lewis base, such as anhydrous ammonia, is passed, as by sparging through the slurry, preferably at a temperature of between 25"C and 65"C to break the insoluble complex and separate the substituted thianthrene in the soluble phase. The amount of Lewis base employed may vary considerably. Essentially complete separation, under the conditions shown may generally be accomplished with the addition of between 0.3 to and 0.5 parts by weight of ammonia per part of crude complex. Aluminum chloride and any residual sulfur form insoluble complexes which are then filtered from the solution. The product substituted thianthrene can then be recovered in high yields by evaporation and crystallization of the liquor.

The most preferred substituted thianthrenes which may be prepared in accordance with this invention are the di- and tetra-substituted thianthrenes wherein the substituents are selected from methyl and chlorine. Such compounds are prepared in the manner described from an appropriately substituted benzene compound having at least two adjacent ring positions unsubsituted. Most preferred are mono and di-substituted benzene compounds wherein the substituents are independently selected from methyl and chlorine. Thus, the preferred substituted benzene compound starting materials include for example, toluene, orthochlorotoluene, parachlorotoluene, metachlorotoluene, paraxylene orthoxylene, metaxylene. The particular substituted thianthrene prepared will depend on the position of the substituents on the benzene ring, and in some instances may be a mixture of substituted thianthrenes. Thus, for example, when paraxylene is employed as the starting material, the product will be 1,4,6,9-tetramethylthianthrene. When the starting material is metaxylene, the product will be a mixture of the 1,3,6,8- and 1,3,7,9-isomers of tetramethylthianthrene.

Various Lewis bases may be employed in recovering the substituted thianthrene from the complex. Typical Lewis bases include for example, ammonia, pyridine and diethylamine.

Based on efficiency, cost and availability, the preferred Lewis base is ammonia. The organic solvent in which the thianthrene compound-aluminum chloride complex is slurried is selected on the basis of three primary considerations. First, the solvent must be-one in which the substituted thianthrene is soluble. Second, the solvent must be substantially inert to ammonia or other Lewis base employed. In addition, the solvent must be one in which the complex is substantially insoluble. Solvents suitable for this purpose include for example, benzene, monochlorobenzene, toluene, monochlorotoluene, tetrahydrofuran, carbon tetrachloride, chloroform, acetylene, tetrachloride, perchloroethylene, trichloroethylene and xylene, as mixtures thereof, and other organic solvents that meet the considerations set forth above. Optionally, all or a part of the solvent employed may be an excess of the substituted benzene compound reactant. Thus, for example, in the preparation of dimethyldichlorothianthrene from sulfur monochloride and orthochlorotoluene in the presence of the orthochlorotoluene may be used and will serve as a solvent for the dimethyldichlorothianthrene when the latter is separated from the complex. Additional amounts of the same or other suitable solvent may be added.

The following Example will serve to further illustrate the invention and the manner in which it may be practised. In the Example, unless otherwise stated, all parts and percentages are by weight.

Example A mixture of 126.5 parts of orthochlorotoluene and 13.35 parts of aluminum chloride was stirred and heated to about 40"C. Stirring was continued and the temperature maintained while 22.5 parts of sulfur monochloride was added slowly to the mixture over a period of about one half hour. After completion of the sulfur monochloride addition, the temperature of the reaction mixture was maintained at about 40"C. Ammonia was then bubbled slowly into the reaction mixture until the reaction mixture changed in color from a dark green-blue to a yellow. At this point 159 parts of chloroform was added and the solution of ammonia was continued until the reaction mixture was found to be alkaline to litmus paper. The mixture was filtered and washed with chloroform. Gas chromatographic analysis of the filtrate indicated a 56.6 percent yield of thianthrene product, based on sulfur monochloride, containing approximately 33 percent dimethylthianthrene, 23 percent dimethylmonochlorothianthrene, and 44 percent dimethyldichlorothianthrene.

WHAT WE CLAIM IS: 1. A process for separating a substututed thianthrene of the formula

wherein each X independently represents hydrogen, methyl, ethyl, chlorine, bromine or fluorine, subject to the proviso that not all X's on each benzene ring are hydrogen, from a complex thereof with aluminum chloride, which process comprising mixing the complex with an organic liquid which is a solvent for the substituted thianthrene but not for the complex or for aluminum chloride to form a slurry of the complex, and treating the slurry with a Lewis base to which the organic liquid is inert to free the substituted thianthrene from the complex and to allow the substituted thianthrene to dissolve in the organic liquid.

2. A process according to claim 1 wherein the Lewis base is ammonia.

3. A process according to claim 1 wherein the Lewis base is diethylamine.

4. A process according to claim 1 wherein the Lewis base is pyridine.

5. A process according to any one of the preceding claims wherein the substituted thianthrene is a dimethyldichlorothianthrene.

6. A process according to any one of the preceding claims wherein the organic liquid is a monochlorotoluene.

7. A process according to any of claims 1 to 5 wherein the organic liquid is chloroform.

8. A process according to any one of the preceding claims wherein the complex has been prepared by adding, in the presence of aluminum chloride, sulphur monochloride to a stoichiometric excess of a substituted benzene compound of the formula

wherein each X independently represents hydrogen, methyl, ethyl, chlorine, bromine or

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Based on efficiency, cost and availability, the preferred Lewis base is ammonia. The organic solvent in which the thianthrene compound-aluminum chloride complex is slurried is selected on the basis of three primary considerations. First, the solvent must be-one in which the substituted thianthrene is soluble. Second, the solvent must be substantially inert to ammonia or other Lewis base employed. In addition, the solvent must be one in which the complex is substantially insoluble. Solvents suitable for this purpose include for example, benzene, monochlorobenzene, toluene, monochlorotoluene, tetrahydrofuran, carbon tetrachloride, chloroform, acetylene, tetrachloride, perchloroethylene, trichloroethylene and xylene, as mixtures thereof, and other organic solvents that meet the considerations set forth above. Optionally, all or a part of the solvent employed may be an excess of the substituted benzene compound reactant. Thus, for example, in the preparation of dimethyldichlorothianthrene from sulfur monochloride and orthochlorotoluene in the presence of the orthochlorotoluene may be used and will serve as a solvent for the dimethyldichlorothianthrene when the latter is separated from the complex. Additional amounts of the same or other suitable solvent may be added. The following Example will serve to further illustrate the invention and the manner in which it may be practised. In the Example, unless otherwise stated, all parts and percentages are by weight. Example A mixture of 126.5 parts of orthochlorotoluene and 13.35 parts of aluminum chloride was stirred and heated to about 40"C. Stirring was continued and the temperature maintained while 22.5 parts of sulfur monochloride was added slowly to the mixture over a period of about one half hour. After completion of the sulfur monochloride addition, the temperature of the reaction mixture was maintained at about 40"C. Ammonia was then bubbled slowly into the reaction mixture until the reaction mixture changed in color from a dark green-blue to a yellow. At this point 159 parts of chloroform was added and the solution of ammonia was continued until the reaction mixture was found to be alkaline to litmus paper. The mixture was filtered and washed with chloroform. Gas chromatographic analysis of the filtrate indicated a 56.6 percent yield of thianthrene product, based on sulfur monochloride, containing approximately 33 percent dimethylthianthrene, 23 percent dimethylmonochlorothianthrene, and 44 percent dimethyldichlorothianthrene. WHAT WE CLAIM IS:

1. A process for separating a substututed thianthrene of the formula

2. A process according to claim 1 wherein the Lewis base is ammonia.

3. A process according to claim 1 wherein the Lewis base is diethylamine.

4. A process according to claim 1 wherein the Lewis base is pyridine.

fluorine, subject to the proviso that not all X's are hydrogen.

9. A process according to claim 8 wherein the substituted benzene compound is orthochlorotoluene.

10. A process according to claim 1 substantially as described with reference to the Examples.

11. A process according to any one of the preceding claims wherein a solution of a substituted thianthrene in an organic liquid is separated from the solids present and the substituted thianthrene is recovered from the solution in known manner.

12. A substituted thianthrene when prepared by a process as claimed in claim 11.