Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Patent
1996-10-22
1998-08-11
Shaver, Paul F.
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
570144, 562493, C07C 1908, C07C 2200, C07C 6304
Patent
active
057928924
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to processes for the preparation of bromine-containing aromatic compounds, to novel bromine-containing compounds and to their use as intermediates in the synthesis of active substances. Processes according to the invention for the preparation of known and of novel bromine-containing compounds are characterized by specific conditions.
The process according to the invention is generally suited to the bromination of aromatic systems. Many aromatic systems can only be subjected to electrophilic bromination under relatively drastic conditions. It is in these cases that the process according to the invention is preferably employed. Examples of such cases are aromatic compounds which are already substituted by electronegative groups and are therefore deactivated. One concrete example is nitrobenzene, but novel bromine-containing compounds are also accessible by the process according to the invention.
The term novel bromine-containing aromatic compounds refers both to compounds which contain the bromine in the aromatic ring system and to compounds in which the bromine is part of a trihalogenomethyl substituent on the aromatic ring system. It refers moreover to compounds which contain the bromine both in the aromatic ring system and in the trihalogenomethyl substituent.
The present invention therefore also relates to compounds of the general formula ##STR1## in which X.sup.1, X.sup.2 and X.sup.3 represent halogen, X.sup.2 and X.sup.3 cannot be fluorine.
3-Bromo-2,4-dichloro-5-fluorobenzotrichloride is preferred.
The aromatic ring system in such bromine-containing aromatic compounds preferably possesses further electron-withdrawing substituents, for example halogens, functional groups at the oxidation state of a carboxylic acid, or nitro groups. Halogen substituents are in particular chlorine and fluorine, and functional groups at the oxidation state of a carboxylic acid are in particular trihalogenomethyl groups, preferably a trichloromethyl group. Concrete examples of the novel bromine-containing aromatic compounds according to the invention are 3-bromo-2,4-dichloro-5-fluorobenzotrichloride (4) and 3-bromo-2,4-dichloro-5-fluorobenzodichloride monobromide (5), which can be used advantageously as intermediates in the synthesis of highly active quinolonecarboxylic acids.
As intermediates for quinolonecarboxylic acids the compounds are used by hydrolysis of the trihalogenomethyl group to give 3-bromo-2,4-dichloro-5-fluorobenzoic acid or by its partial hydrolysis to give the corresponding 3 -bromo-2,4-dichloro-5-fluorobenzoyl chloride or bromide.
3-Bromo-2,4-dichloro-5-fluorobenzoic acid and 3-bromo-2,4-dichloro-5-fluorobenzoyl chloride are known as intermediates for highly active quinolonecarboxylic acids and can be prepared, in accordance with DE-A 3 631 906, by nitrating 2,4-dichloro-5-fluorobenzoic acid in position 3, hydrogenating the product to give the amino compound, and introducing bromine by way of a Sandmeyer reaction. The numerous and laborious reaction steps make this route very expensive.
It has now surprisingly been found that 2,4-dichloro-5-fluorobenzotrichloride (1), an industrial intermediate for quinolonecarboxylic acids, can be brominated directly in position 3 under specific conditions with outstanding space-time yield in a process in which, depending on the reaction conditions, the product is, with a substantial degree of uniformity, the novel 3-bromo-2,4-dichloro-5-fluorobenzo-trichloride (4), or the analogous dichloromonobromomethyl compound formed by bromine/chlorine exchange in the side chain, as an additional, novel intermediate. Both compounds can be hydrolysed to give the carboxylic acid or, respectively, the carboxylic halide, in analogy to known processes.
2,4-Dichloro-5-fluorobenzyl chloride which is formed during the hydrolysis from any unreacted 2,4-dichloro-5-fluorobenzotrichloride (1) can readily be removed by distillation and is likewise an intermediate for the preparation of quinolonecarboxylic acids.
The process according to the invention is carried o
REFERENCES:
patent: 2607802 (1952-08-01), Britton et al.
patent: 5565612 (1996-10-01), Pfirmann et al.
Bayer Aktiengesellschaft
Shaver Paul F.
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