Organic compounds -- part of the class 532-570 series – Organic compounds – Sulfur containing
Reexamination Certificate
1999-08-27
2002-04-02
Rotman, Alan L. (Department: 1612)
Organic compounds -- part of the class 532-570 series
Organic compounds
Sulfur containing
C546S294000, C546S153000, C568S032000
Reexamination Certificate
active
06365780
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for the preparation of aromatic or heteroaromatic sulphonyl chlorides by diazotization of amino-substituted aromatics or heteroaromatics and decomposition of the resulting diazonium salts in the presence of sulphur dioxide.
BACKGROUND OF THE INVENTION
Aromatic sulphonyl chlorides are important intermediates for crop-protection products, pharmaceuticals and dyes. From Chem. Ber. 90, 1957, p. 841, it is known to prepare this class of compound by diazotization of the corresponding aromatic amines with aqueous sodium nitrite solutions and decomposition of the diazonium salts in solutions of sulphur dioxide, copper salts and acetic acid. Where appropriate, a water-immiscible organic solvent is also added so that the reaction mixture is two-phase. This process does, however, have a number of disadvantages. For example, the yields are unsatisfactory in many cases. While electron-withdrawing groups, as further substituents in the diazonium salts, have a favourable effect on the yield and the reaction rate, the use of diazonium salts, which carry electron-donating substituents, leads only to low yields. In addition, when the reaction is carried out on an industrial scale, large amounts of wastewater which contains copper and acetic acid are formed. The processing and disposal of such wastewater is costly and is not possible using an economic process. If diazonium salts containing electron-withdrawing substituents on the aromatic ring are used, such as dinitrobenzene-diazonium chlorides, it is in some circumstances also possible to carry out the process without the copper salts as catalyst. Although the yields in this case are not much lower than in the presence of the catalyst, the reaction rate does drop considerably.
German Offenlegungsschrift 2,308,262 discloses a further process for the preparation of aromatic sulphonyl chlorides in which the sulphur dioxide is used in the form of alkali metal hydrogen sulphite in the presence of copper or copper salts. The addition of acetic acid or other organic solvents is not necessary here, the aromatic diazonium salts are used in strong hydrochloric acid solution. According to EP-A-0,059,241, the reaction of the aqueous diazonium salt solution with sulphur dioxide is carried out in the presence of a solvent which is immiscible or miscible only to a limited extent with water, and copper salts as catalyst, and subsequently the reaction mixture is treated with an oxidizing agent.
Although these processes avoid the problem of wastewater containing acetic acid being produced, as a result of the diazotization of the anilines in an aqueous medium and the use of dilute aqueous diazonium salt solutions in the reaction with the sulphur dioxide in the presence of copper, large amounts of wastewater containing copper salts are again formed. Furthermore, the space-time yield of these processes is unsatisfactory as a result of the use of dilute aqueous diazonium salt solution and the large volumes which arise as a result. In addition, the handling of the diazonium salt solutions requires specific precautionary measures because of the decomposability of the diazonium salts. For example, these solutions must be handled at low temperatures around 0° C. and be processed quickly in order to limit yield losses in industrial operation.
All of the abovementioned processes have the common disadvantage that the conversion of the anilines into the corresponding aromatic sulphonyl chlorides takes place in two stages. In the first stage, the diazotization of the aniline with aqueous sodium nitrite solution takes place, and in the second stage, the decomposition of the diazonium salt in the presence of sulphur dioxide or alkali metal hydrogen sulphite, a copper compound and, where appropriate, an organic solvent.
There is therefore a need for a process which permits the preparation of aromatic or heteroaromatic sulphonyl chlorides from the parent anilines or amino-substituted pyridines in a simple manner with a high chemical yield, a high space-time yield, coupled with the formation of only a small amount of wastewater.
DESCRIPTION OF THE INVENTION
The invention provides a process for the preparation of aromatic or heteroaromatic sulphonyl chlorides of the general formula I
in which
X may be a C or N,
R
1
may be fluorine, chlorine, bromine, nitro, methoxy, fluoromethoxy, difluoromethoxy, trifluoromethoxy, C
1
-C
4
alkyl or phenyl, and
R
2
may be H, fluorine, chlorine, bromine, OH or C
1
-C
4
alkyl, by diazotization of the compounds of the general formula II
in which
X, R
1
and R
2
are as defined for formula (I), and decomposition of the resulting diazonium salts in the presence of sulphur dioxide and a copper catalyst, characterized in that the compounds of the formula (II) are treated, in a mixture with one or more organic solvents, sulphur dioxide and a copper catalyst, with hydrogen chloride and alkyl nitrite at temperatures of from −20 to +60° C.
If, in the formulae (I) and (II), R
1
and R
2
are C
1
-C
4
alkyl, these alkyl radicals may be straight-chain or branched, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl and tert-butyl may be used.
In the formulae (I) and (II), R
1
is preferably fluorine, chlorine, bromine, nitro, methoxy, trifluoromethoxy, methyl or ethyl, and R
2
is preferably hydrogen, fluorine, chlorine, bromine, methyl or ethyl.
In the formulae (I) and (II), R
1
is particularly preferably fluorine, chlorine, bromine, nitro or trifluoromethoxy, and R
2
is particularly preferably hydrogen.
If the compounds of the formula (II) are substituted anilines, i.e., X is C, the substituents R
1
and R
2
are then preferably in the 2- and/or 4-position relative to the amino radical. If the compounds of the formula (II) are substituted amino-pyridines, i.e., X is N, then the amino radical is preferably in the 3-position, and the substituents R
1
and R
2
are preferably in the 2- and/or 6-position.
Specific examples of compounds of the formula (II) on which the process of the invention can be used advantageously are 2-nitroaniline, 4-nitroaniline, 2-trifluoromethoxyaniline and 3-amino-2-chloropyridine. These compounds are available commercially.
Suitable organic solvents for the process of the invention are those which are essentially inert under the reaction conditions and at least partly dissolve the starting materials of the formula (I), sulphur dioxide, hydrogen chloride and the copper catalyst. Examples of such solvents are aromatic hydrocarbons, alcohols, ethers, halogenated hydrocarbons, sulphoxides and sulphones. Such solvents can be used individually or as mixtures of two or more solvents.
Preference is given to using aromatic hydrocarbons, for example, toluene, xylene, ethyl benzene, halogenated hydrocarbons, such as methylene chloride, 1,2-dichloroethane, chlorobenzene or dichlorobenzene, alcohols, such as methanol, ethanol, 1-propanol, 2-propanol, isomeric butanols, isomeric pentanols or isomeric hexanols, or ethers, such as methyl tert-butyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether or polyethylene glycol dimethyl ether as solvent.
Such solvents can also be used in mixtures with water. The addition of water can in some cases favour the solubilities of the starting materials. Here, it is insignificant whether such mixtures form one or two liquid phases. However, the addition of water is limited to small amounts of from 0.1 to 0.5 part by weight, based on the total amount of the organic solvent, depending on the process.
The amount of solvent is such that readily stirrable solutions or suspensions are obtained and, depending on its solubilizing power for the starting components, is advantageously 1-20 parts by weight, preferably 1.5-10 parts by weight, based on the compounds of the formula (II).
In order to obtain the highest possible yields of sulphonyl chlorides of the formula (I), it is expedient to use at least equimolar amounts of sulphur dioxide based on the
Hermann Monika
Schnatterer Albert
Bayer Aktiengesellschaft
Eyl Diderico van
Gil Joseph C.
Rotman Alan L.
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