Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1999-09-10
2000-11-21
Davis, Zinna Northington
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C07D21338
Patent
active
061505285
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the preparation of 5-aminomethyl-2-chloropyridines by reacting a mixture of 5-chloromethyl-2-chloropyridine and 5-dichloromethyl-2-chloropyridine with substituted amines. The mixture of 5-chloromethyl-2-chloropyridine and 5-dichloromethyl-2-chloropyridine is obtained by chlorination of the 5-methyl-2-chloropyridine.
The reaction of 5-chloromethyl-2-chloropyridine with amines to give substituted 5-aminomethyl-2-chloropyridines is known. However, for this purpose, it is necessary to prepare the starting material 5-chloromethyl-2-chloropyridine in high purity. To this end, 5-methyl-2-chloropyridine is chlorinated. In order to prevent the formation of more highly chlorinated pyridines such as 5-dichloro- or 5-trichloromethyl-pyridines, the chlorination must be terminated at low conversions. The resulting product then contains high amounts of starting material which must be removed and returned to the halogenation. Carrying out this reaction in industry is expensive.
It has become known that 5-aminomethyl-2-chloropyridines are also obtained when 5-trichloromethyl-2-chloromethylpyridine is reacted with amines under reducing conditions. However, this produces large amounts of salt-containing wastewater--3 mol of chloride are produced per mole of aminomethylpyridine, which must be disposed of, which is costly. In addition, the yields of this process are not always satisfactory.
It has now been found that 5-aminomethyl-2-chloropyridines of the formula (I) ##STR1## in which R is hydrogen or optionally substituted C.sub.1 -C.sub.4 -alkyl are obtained when, in a first stage, 5-methyl-2-chloropyridine in the form of its salt is chlorinated using inorganic acids optionally in the presence of a diluent at temperatures between 50 and 150.degree. C., preferably in the presence of a free-radical former until the content of 5-methyl-2-chloropyridine is <about 3%, and then, optionally after the diluent has been removed, in a second stage, the resulting reaction mixture is reacted with amine of the formula (II) reducing conditions.
The novel process avoids the complex selective chlorination of 5-ethyl-2-chloropyridine and the equally complex purification and separation procedures. The novel process avoids the formation of large amounts of salt-containing wastewater.
It was not to be expected that the reaction of the reaction mixture of 5-chloromethyl and 5-dichloromethyl-2-chloropyridine with amine produces the desired 5-amino-2-chloropyridine in good yields and high purity. It was completely surprising that the reaction using the mixture produces even better yields than when the corresponding pure trichloromethyl- or dichloromethylpyridines are used.
Furthermore, it was surprising that under reducing conditions, cleavage of the 2-chlorine atom on the pyridine ring is suppresssed.
In formula (I), R is preferably hydrogen or C.sub.1 -C.sub.4 -alkyl, which is optionally substituted by OH, NH.sub.2 or --NHR.
R is, in particular, methyl, ethyl, n-, iso-propyl, n-butyl, which are optionally substituted by OH, NH.sub.2 or --NH--(C.sub.1 -C.sub.4)-alkyl.
R is particularly preferably ethyl or n-propyl which are substituted by OH, NH.sub.2 or --NHCH.sub.3.
In the first stage, the salts of 5-methyl-2-chloropyridine used are preferably hydrochloride or sulphate. Particular preference is given to the hydrochloride.
The chlorination is carried out either in the presence of diluents or without diluents in the melt. Diluents which may be mentioned are chlorinated hydrocarbons such as, for example, tetrachloromethane, or else acetonitrile or water.
The chlorination is carried out at about 50-150.degree. C., preferably at 70-120.degree. C.
The chlorination can preferably be carried out in the presence of a free-radical former, such as azoisobutyronitrile or a peroxide such as benzoyl peroxide.
The course of the chlorination is continually monitored, for example by gas chromatography. The chlorination is terminated when the content of 5-methyl-2-chloropyridine has dropped below about 3%.
At this point, a mixt
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Lantzsch Reinhard
Stelzer Uwe
Bayer Aktiengesellschaft
Davis Zinna Northington
Gil Joseph C.
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