Organic compounds -- part of the class 532-570 series – Organic compounds – Sulfur containing
Reexamination Certificate
1993-08-12
2001-07-10
Higel, Floyd D. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Sulfur containing
C562S125000
Reexamination Certificate
active
06258984
ABSTRACT:
The invention relates to a process for the preparation of 4-alkyl(C
1
-C
4
)-sulfonyl-1-alkyl(C
1
-C
4
)-2-chlorobenzenes, in particular 4-methylsulfonyl-1-methyl-2-chlorobenzene, where the 4-alkyl(C
1
-C
4
)-3-chlorobenzenesulfinic acids formed as intermediates in this process and the end products obtained, except for 4-methylsulfonyl-1-methyl-2-chlorobenzene (U.S. Pat. No. 4,675,447), are novel compounds.
The compounds are valuable intermediates for pesticides and herbicides.
Preparation of 4-alkylsulfonyl-1-alkyl-2-chlorobenzenes by chlorination of 4-alkylsulfonylalkylbenzenes with sulfuryl chloride in the presence of antimony chloride as a catalyst is known (U.S. Pat. No. 4,675,447).
Disadvantages of this are the use of relatively expensive sulfuryl chloride, substantial production of the environmentally polluting sulfur dioxide and the preparation of isolated, dry 4-alkylsulfonylalkylbenzenes.
It has now surprisingly been found that 4-alkylsulfonyl-1-alkyl-2-chlorobenzenes of the formula (4)
in which R
1
and R
2
are identical or different alkyl groups having 1 to 4 carbon atoms, may be prepared, avoiding the disadvantages associated with the process of the prior art, in very good yields and in high selectivity by selectively chlorinating 1 mol of a p-alkylbenzene-sulfonyl chloride of the formula (1)
in which R
1
has the meaning given above, with at least 1 mol of gaseous chlorine in the presence of a chlorine carrier, such as for example iron(III) chloride or iron(III) chloride and iodine, at temperatures of about 50° C. to about 100° C., preferably of about 70° C. to about 80° C. to give the compound of the formula (2)
in which R
1
has the meaning given above, reducing the latter exclusively in an aqueous medium at a pH of about 8 to 10 with 1 to about 1.2 mol, preferably 1.1 mol, of sodium hydrogen sulfite or sodium sulfite at temperatures of about 40 to about 90° C., preferably of about 50 to about 65° C., to give a compound of the formula (3)
in which R
1
has the meaning given above, and reacting the latter with 1 to about 2.2 mol, preferably about 1.25 to about 1.90 mol, particularly preferably about 1.50 to about 1.75 mol, of alkyl(C
1
-C
4
) chloride, in the presence of an acid binder, preferably magnesium oxide, to give the compound of the formula (4) mentioned above, at temperatures of about 80 to about 150° C.
The process according to the invention is carried out in detail as described below.
a) Chlorination:
Chlorination of the p-alkyl (C
1
-C
4
)-benzenesulfonyl chloride advantageously is carried out in the absence of solvents by passing through elemental chlorine at about 50-100° C., preferably at 70-80° C., with the use of about 0.1 to about 1%, preferably about 0.5%, of a catalyst mixture of 75% of iron(III) chloride and 25% of iodine. Chlorination is terminated at a degree of monochlorination of approximately 100%. (End point determination via GC). The resulting product contains, in addition to traces of the starting compound, only very small quantities of the dichloro compound. The chlorination product can be used for further processing in the form in which it occurs; however, it can also be washed, distilled or fractionated. The yield of 3-chloro-4-alkyl(C
1
-C
4
)benzene-sulfonyl chlorides is virtually quantitative.
b) Reduction:
Reduction of the 2-chloro-4-alkyl(C
1
-C
4
)benzenesulfonyl chlorides obtained according to a) to the 4-alkyl(C
1
-C
4
)-3-chlorobenzenesulfinic acids can be carried out by a method known per se (cf. Houben-Weyl, Vol. 9, pp. 304-311). The reduction is advantageously carried out using NaESO
3
+NaOH, preferably using sodium sulfite+NaOH. The reduction is optimally carried out in an aqueous medium by simultaneously adding 2-chloro-4-alkylbenzene-sulfonyl chloride (in the molten state) and sodium hydroxide solution (commercially available 35% strength) dropwise to a solution of sodium sulfite with pH monitoring at from about 8 to about 10. The sulfonyl chloride can also be added to the sulfite solution, and the sodium hydroxide solution can be added with the pH maintained at about 8 to about 10. The concentration of the sulfite solution can vary between about 10 and about 30%, preference being given to an approximately 15% strength solution. The amount of sulfite varies between the theoretical amount and an excess of about 20%, an excess of about 10% being most expedient. The reaction proceeds at a temperature of about 40 to about 90° C., preferably between about 50 and about 65° C. The reduction is complete when the pH remains constant at a value of about 8 to about 10. The sodium salt of the 4-alkyl-(C
1
-C
4
)-3-chlorobenzenesulfinic acid crystallizes out from the solution at about 45° C. The compound can be further processed without intermediate isolation.
c) Alkylation:
Alkylation of the 4-alkyl(C
1
-C
4
)-3-chlorobenzenesulfinic acids (Na salts) obtained according to b) to give the corresponding 4-alkyl (C
1
-C
4
)-sulfonyl-2-chloroalkyl-benzenes takes place using alkyl(C
1
-C
4
) chlorides, preferably methyl chloride. To carry out this reaction, the reduction solution obtained according to b) (isolation of the sulfinate is not necessary) is placed in a pressure apparatus (autoclave), and the corresponding alkyl(C
1
-C
4
) chlorides and an acid binder, preferably magnesium oxide, for neutralization of the hydrogen chloride produced from the hydrolysis of the excess alkyl(C
1
-C
4
) chloride, are added. The amount of the alkyl(C
1
-C
4
) chlorides used varies in the range from about 100 to about 220% of theory, advantageously between about 125 and about 190%, particularly preferably between about 150 and about 175%. The alkyl chlorides can be added all at once, or in portions or continuously during the reaction. The reaction temperatures for methylation are in the range from about 80 to about 100° C. With the use of alkyl(C
4
) chlorides, a reaction temperature of about 150° C. is required.
The acid binders used can be, apart from magnesium oxide, for example, the hydroxide, carbonate or hydrogen carbonate of metals selected from the group comprising lithium, sodium, potassium, rubidium, caesium, magnesium, calcium, barium and strontium, or mixtures of these compounds.
The following examples are intended to illustrate the process according to the invention in more detail, without restricting it thereto.
REFERENCES:
patent: 4012442 (1977-03-01), Blank et al.
patent: 4675447 (1987-06-01), Ludvik
patent: 4825005 (1989-04-01), Frey et al.
patent: 133000 (1902-07-01), None
patent: 0 115 328 (1984-08-01), None
patent: 0 258 190 (1988-03-01), None
patent: 162064 (1988-03-01), None
patent: 165445 (1989-10-01), None
patent: 91/07384 (1991-05-01), None
Methoden Der Organischen Chemie, (Houben-Weyl), Vol. IX, pp. 306-307 (1955).
Folz Georg
Papenfuhs Theodor
Clariant GmbH
Connolly Bove & Lodge & Hutz LLP
Higel Floyd D.
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