Method for the nuclear chlorination of ortho-xylene
View Patent ↗A method for the nuclear chlorination of ortho-xylene using a chlorinating agent in the presence of at least one Friedel-Crafts catalyst and chloro-substituted 2,8-dimethylphenoxathiin as co-catalyst. The co-catalyst used is preferably tetrachlorinated 2,8-dimethylphenoxathiin, in particular 1,3,7,9-tetrachloro-2,8-dimethylphenoxathiin of the formula
1. A method for the nuclear chlorination of ortho-xylene, which comprises reacting ortho-xylene with a chlorinating agent in the presence of at least one Friedel-Crafts catalyst and chlorine-substituted 2,8-dimethylphenoxathiin as co-catalyst, wherein the ratio of 4-chloro- to 3-chloro-1,2-dimethylbenzene is at least 3:1.
2. The method as claimed in claim 1 , wherein tetrachlorinated 2,8-dimethylphenoxathiin is used.
3. The method as claimed in claim 1 , wherein elemental chlorine or sulfuryl chloride is used as chlorinating agent.
4. The method as claimed in claimed in claim 1 , wherein the co-catalyst is used in an amount of from 0.001 to 5% by weight, based on the amount of the ortho-xylene used.
5. The method as claimed in claim 1 , wherein the ratio of Friedel-Crafts catalyst or its precursor to the co-catalyst is in the range from 500:1 to 1:5.
6. The method as claimed in claim 1 , wherein the method is carried out without addition of a solvent.
7. The method as claimed in claim 1 , wherein the method is carried out at a temperature in the range from −20 to +120° C.
8. The method as claimed in claim 1 , wherein the amount of the chlorinating agent used is selected such that a degree of chlorination of significantly greater than 1 results.
9. The method as claimed in claim 2 , wherein 1,3,7,9-tetrachloro-2,8-dimethylphenoxathiin of the formula
is used.
10. The method as claimed in claim 2 , wherein elemental chlorine or sulfuryl chloride is used as chlorinating agent.
11. The method as claimed in claim 2 , wherein the co-catalyst is used in an amount of from 0.001 to 5% by weight, based on the amount of the ortho-xylene used.
12. The method as claimed claim 2 , wherein the ratio of Friedel-Crafts catalyst or its precursor to the co-catalyst is in the range from 500:1 to 1:5.
13. The method as claimed claim 3 , wherein the method is carried out without addition of a solvent.
14. The method as claimed in claim 3 , wherein the method is carried out at a temperature in the range from −20 to +120° C.
15. The method as claimed in claim 3 , wherein the amount of the chlorinating agent used is selected such that a degree of chlorination of significantly greater than 1 results.