Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1999-02-17
2000-12-12
Tsang, Cecilia
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
560103, C07C 51363
Patent
active
061601713
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/JP97/02856 filed Aug. 19, 1997.
TECHNICAL FIELD
This invention relates to a trifluoro-substituted benzoic acid, esters thereof and the processes for preparing the same, more specifically, to a 2,3,4-trifluoro-5-substituted benzoic acid, esters thereof and the novel processes for preparing the same and 2,4,5-trifluoro-3-substituted benzoic acid esters.
BACKGROUND ART
The above-mentioned trifluoro-substituted benzoic acid and esters thereof are useful as a starting material for preparing 2,3,4-trifluoro-5-trifluoromethylbenzoic acid or 2,4,5-trifluoro-3-trifluoromethylbenzoic acid which is an important intermediate for synthesis of quinolone carboxylic acids useful as, for example, a medicine, particularly as an anti-bacterial or antiviral agent. Trifluoro-trifluoromethylbenzoic acids can be converted into quinolone carboxylic acids having a 6- or 8-trifluoromethyl group according to the method as disclosed in, for example, WO 96/02512 publication or Japanese Provisional Patent Publication No. 66180/1989.
As methods for preparing 2,4,5-trifluoro-3-iodobenzoic acid derivatives which are starting materials for producing 2,4,5-trifluoro-3-trifluoromethylbenzoic acid, it has been known the method for preparing 2,4,5-trifluoro-3-iodobenzoic acid from 3-amino-2,4,5-trifluorobenzoic acid by the Sandmeyer's reaction. More specifically, the methods shown below may be mentioned.
(1) In Japanese Provisional Patent Publication No. 95176/1991, there is disclosed a method for obtaining 2,4,5-trifluoro-3-iodobenzoic acid by reacting cuprous iodide, tert-butyl nitrite and 3-amino-2,4,5-trifluorobenzoic acid in acetonitrile.
(2) In Japanese Provisional Patent Publication No. 88157/1988 and Japanese Provisional Patent Publication No. 25125/1994, there are disclosed a method for obtaining 2,4-dichloro-5-fluoro-3-iodobenzoic acid by reacting 3-amino-2,4-dichloro-5-fluorobenzoic acid with hydrochloric acid and sodium nitrite to once form a diazonium salt, and then, reacting it with potassium iodide.
However, in the above-mentioned method (1), many side reactions proceed and the yield is 50% or less, and thus, it is not an industrially satisfied method. Also, the above-mentioned method (2) is not an industrially satisfied method in the point that the yield is less than 60%.
Accordingly, neither of the known method (1) or (2) is satisfactory as a method for obtaining 2,4,5-trifluoro-3-iodobenzoic acid.
Also, in Japanese Provisional Patent Publication No. 66180/1989 and WO 96/02512 publication, there is disclosed a method for preparing 2,4,5-trifluoro-3-trifluoromethyl-benzoic acid by lithiating 1-bromo-2,4,5-trifluoro-3-trifluoromethylbenzene with n-butyl lithium, etc., and incorporating the carboxyl group by carbon dioxide.
However, the above-mentioned method has the following disadvantageous points. That is,
(1) It has been reported that lithium compounds having a trifluoromethyl group at the benzene ring, such as m-trifluoromethylphenyl lithium even without fluorine substituent has an explosive property, and still more polyfluorophenyl lithium also has an explosive property (see Chemistry and Industry, p. 1017 (1971), Chem. Eng. News, 1961, vol. 39, No. 16, p. 43).
(2) It has been reported that a trifluoromethylphenyl magnesium compound obtained from a trifluoromethylhalobenzene by the Grignard reaction shows the similar reactivity as that of the above-mentioned lithium compound and a carboxyl group can be introduced by carbon dioxide, but the compound also has an explosive property. (see Chemistry and Industry, p. 120 (1971)).
Accordingly, it can be expected as a matter of course that 2,4,5-trifluoro-3-trifluoromethylphenyl lithium which is obtained by lithiating 1-bromo-2,4,5-trifluoro-3-trifluoromethylbenzene also has an explosive property. In the conventionally known methods, it is expected to cause an explosion during the process which is a significant problem in industrial production, so that it is not quite satisfactory as a method for producing 2,4,5-trifluoro-3-trifluoromethylbenz
Ataka Kikuo
Yamamoto Yasuhito
Yokota Naoyuki
Yoneda Yasuhiro
Solola Taofiq A.
Tsang Cecilia
Ube Industries Ltd.
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