CN110759831B - Method for preparing halofuginone intermediate 2-amino-4-bromo-5-chlorobenzoic acid - Google Patents

Method for preparing halofuginone intermediate 2-amino-4-bromo-5-chlorobenzoic acid Download PDF

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CN110759831B
CN110759831B CN201910982668.3A CN201910982668A CN110759831B CN 110759831 B CN110759831 B CN 110759831B CN 201910982668 A CN201910982668 A CN 201910982668A CN 110759831 B CN110759831 B CN 110759831B
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chlorobenzoic acid
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王金娟
蒋健
陆小丽
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ZHEJIANG GENEBEST PHARMACEUTICAL CO Ltd
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    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/347Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups
    • C07C51/363Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups by introduction of halogen; by substitution of halogen atoms by other halogen atoms
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    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C201/00Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
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    • C07C201/08Preparation of nitro compounds by substitution of hydrogen atoms by nitro groups
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    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C227/00Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton
    • C07C227/04Formation of amino groups in compounds containing carboxyl groups
    • C07C227/06Formation of amino groups in compounds containing carboxyl groups by addition or substitution reactions, without increasing the number of carbon atoms in the carbon skeleton of the acid

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Abstract

A preparation method of an anticoccidial drug halofuginone intermediate, which relates to a preparation method of a specific compound 2-amino-4-bromo-5-chlorobenzoic acid. The method sequentially comprises the following steps: the p-bromobenzoic acid is adopted as a raw material, and a product is obtained through chlorination, nitration and selective reduction reactions. The invention provides a new synthesis route and reaction conditions, the used raw materials are sufficient in market supply and wide in source, the reaction conditions in each step are mild, the process is simple, the requirements of green production are met, and the production cost is effectively reduced.

Description

Method for preparing halofuginone intermediate 2-amino-4-bromo-5-chlorobenzoic acid
Technical Field
The invention relates to a preparation method of an anticoccidial drug halofuginone intermediate, and particularly relates to a method for preparing a compound 2-amino-4-bromo-5-chlorobenzoic acid.
Background
Dichrone is a derivative of dichroine extracted from Chinese traditional medicine dichroa febrifuga. The hydrobromide salt of halofuginone was developed and manufactured by Roussel-Uelaf, France under the trade name Sudan as a 0.6% premix of halofuginone hydrobromide. The composition is mainly used for preventing and treating coccidiosis and malaria of domesticated animals such as livestock and poultry (turkey, sheep, goat, cattle and rabbit).
The asymmetric synthesis of halofuginone compounds has begun since the 90 s of the last century and various methods have been used to date to produce this type of compound. Most of these methods, however, require more severe reaction conditions such as: the commercialization of halofuginone is greatly limited by the preparation at a low temperature of-78 ℃ and rare earth metal catalysts, or parts of the method have expensive raw materials, long steps and low overall yield, wherein 2-amino-4-bromo-5-chlorobenzoic acid is used as a key intermediate of the whole route, and the process and the cost directly restrict the whole route of halofuginone.
The patent summarizes a brand-new synthesis route through a series of experiments, and the product is obtained by chlorination, nitration and selective reduction reaction by taking p-bromobenzoic acid as a raw material. The method greatly improves the selectivity of the reaction, obviously improves the yield and the product quality, and effectively controls the cost of the product.
Disclosure of Invention
The invention aims to provide a preparation method of halofuginone intermediate 2-amino-4-bromo-5-chlorobenzoic acid, which has the advantages of simple process, convenient operation and no environmental pollution.
In order to achieve the purpose, a series of experiments are carried out, and a brand new synthetic route is provided.
The technical scheme for realizing the invention is as follows:
a new method for preparing the halofuginone intermediate 2-amino-4-bromo-5-chlorobenzoic acid is characterized in that: the halofuginone intermediate 2-amino-4-bromo-5-chlorobenzoic acid represented by formula (I) is obtained as follows:
Figure 832398DEST_PATH_IMAGE001
(Ⅱ) (Ⅲ) (Ⅰ)
preparation of 3-chloro-4-bromobenzoic acid (II)
Adding 1 time of p-bromobenzoic acid, 0.73-0.74 time of anhydrous aluminum trichloride (weight ratio) and 5-10 times of 1,1, 2-trichloroethane (weight ratio) into a reactor with a stirring and heating device. Cooling to 0 ℃ after uniform stirring, introducing 0.35-0.43 time (weight ratio) of chlorine, heating to 80 ℃, continuing to stir for 8-12 hours, cooling to room temperature after the reaction is finished, filtering to remove insoluble substances, distilling under reduced pressure to remove most of solvent, adding obtained residue into petroleum ether, stirring for 30 minutes, filtering and collecting precipitated solid which is a crude product of 3-chloro-4-bromobenzoic acid (II), detecting the content by HPLC (high performance liquid chromatography) to be more than 95%, and directly using the crude product in the next reaction without further purification.
B.preparation of 2-nitro-4-bromo-5-chlorobenzoic acid (III)
Adding 1 time of 3-chloro-4-bromobenzoic acid (II) and 5-6 times of concentrated sulfuric acid (weight ratio) into a reactor, uniformly stirring, cooling to 0-5 ℃, then dropwise adding 3.23-3.52 times (weight ratio) of concentrated sulfuric acid solution of HNO3 with the mass fraction of 10%, keeping the temperature of the mixture at 0-5 ℃ in the dropwise adding process, continuously stirring for 30 minutes after the dropwise adding is finished, removing the ice bath, naturally heating to room temperature, then heating to 50 ℃, continuously stirring and reacting for 6-10 hours, after the reaction is finished, slowly pouring the mixture into a large amount of ice water, controlling the temperature within 30 ℃, stirring for 30 minutes, filtering and collecting separated solid which is a crude product of the 2-nitro-4-bromo-5-chlorobenzoic acid (III), detecting the content by HPLC to be more than 95%, and directly using the crude product in the next reaction without further purification.
Preparation of C.2-amino-4-bromo-5-chlorobenzoic acid (I)
Adding 1 time of 2-nitro-4-bromo-5-chlorobenzoic acid (III), 0.02-0.05 time of ferric chloride, 0.35-0.55 time of hydrazine hydrate solution with the mass fraction of 50% and 3-6 times of deionized water into a reactor, stirring and reacting for 6-12 hours at room temperature, adjusting the pH to 12 by using 5% sodium hydroxide solution after the reaction is finished, filtering to remove insoluble substances, adjusting the pH of filtrate to 7 by using 10% glacial acetic acid, stirring for 30 minutes, filtering and collecting precipitated solid which is 2-amino-4-bromo-5-chlorobenzoic acid (I) crude product, detecting the content to be more than 95% by HPLC, and directly using the crude product in the subsequent reaction step for preparing halofuginone without further purification. The crude product is recrystallized by a methanol-water mixed solution to obtain a refined product of the 2-amino-4-bromo-5-chlorobenzoic acid (I).
The invention has the advantages that:
1. the invention adopts a brand new synthesis route, improves the selectivity of each step of reaction, and effectively improves the utilization rate and the total yield of raw materials.
2. The raw materials adopted by the method are all sold in the market, the reactions in each step are all conventional operations, the reaction conditions are mild, the control is easy, the cost is reduced, and the product competitiveness is improved.
Detailed Description
How this invention can be carried out is further illustrated by the following specific examples:
example 1
Preparation of 3-chloro-4-bromobenzoic acid (II)
P-bromobenzoic acid (201 g, 1.0 mol), anhydrous aluminum trichloride (147g, 1.1mol) and 1,1, 2-trichloroethane (2000g) were charged to a reactor equipped with stirring and heating means. Cooling to 0 ℃ after uniform stirring, introducing chlorine (85.2 g, 1.2 mol), heating to 80 ℃, continuing to stir for 12 hours, cooling to room temperature after the reaction is finished, filtering to remove insoluble substances, distilling under reduced pressure to remove most of solvent, adding obtained residue into petroleum ether, stirring for 30 minutes, filtering and collecting separated solid which is 214.8g of 3-chloro-4-bromobenzoic acid (II), wherein the yield is about 91.2%, the content is higher than 95% through HPLC (high performance liquid chromatography) detection, and the solid can be directly used for the next reaction without further purification.
B.preparation of 2-nitro-4-bromo-5-chlorobenzoic acid (III)
Adding 3-chloro-4-bromobenzoic acid (II) (235.5 g, 1.0 mol) and concentrated sulfuric acid (1400 g) into a reactor, uniformly stirring, cooling to 0-5 ℃, then dropwise adding concentrated sulfuric acid solution (825 g) of HNO3 with the mass fraction of 10%, keeping the temperature of the mixture at 0-5 ℃ in the dropwise adding process, continuously stirring for 30 minutes after the dropwise adding is finished, removing an ice bath, naturally heating to room temperature, then heating to 50 ℃, continuously stirring for reaction for 10 hours, slowly pouring the mixture into a large amount of ice water after the reaction is finished, controlling the temperature within 30 ℃, filtering and collecting precipitated solid after stirring for 30 minutes, wherein the precipitated solid is 231.2g of 2-nitro-4-bromo-5-chlorobenzoic acid (III), the yield is about 82.4%, the content is higher than 95% through HPLC (HPLC), and the solid can be directly used for the next reaction without further purification.
A small amount of crude product is taken to be refined by methanol and then detected, 1 HNMR(DMSO,400 MHz):8.27(s,1H),8.74(s,1H)。FAB-MS(m/z)::281.5 (M+H)。
preparation of C.2-amino-4-bromo-5-chlorobenzoic acid (I)
Adding 2-nitro-4-bromo-5-chlorobenzoic acid (III) (280.5 g, 1.0 mol), ferric chloride (12.5 g), 50% hydrazine hydrate solution (150 g) and deionized water (1650 g) into a reactor, stirring for reaction at room temperature for 12 hours, adjusting the pH to 12 with 5% sodium hydroxide solution after the reaction is finished, filtering to remove insoluble substances, adjusting the pH to 7 with 10% glacial acetic acid, stirring for 30 minutes, filtering to collect separated solid which is 236.8g of 2-amino-4-bromo-5-chlorobenzoic acid (I), wherein the yield is about 94.5%, the content is higher than 95% by HPLC (high performance liquid chromatography), and the solid can be directly used for the subsequent reaction step of preparing halofuginone without further purification. The crude product is recrystallized by a methanol-water mixed solution to obtain a refined product of the 2-amino-4-bromo-5-chlorobenzoic acid (I).
1 HNMR(DMSO,400 MHz):7.07(s,1H),7.79(s,1H)。FAB-MS(m/z)::251.5 (M+H)。
Example 2
The procedure is otherwise the same as in example 1, except that 3-chloro-4-bromobenzoic acid (II) is prepared as follows:
p-bromobenzoic acid (201 g, 1.0 mol), anhydrous aluminum trichloride (147g, 1.1mol) and 1,1, 2-trichloroethane (1050g) were charged to a reactor equipped with stirring and heating means. Cooling to 0 ℃ after uniform stirring, introducing chlorine (71 g, 1.0 mol), heating to 80 ℃, continuing to stir for 8 hours, cooling to room temperature after the reaction is finished, filtering to remove insoluble substances, distilling under reduced pressure to remove most of solvent, adding the obtained residue into petroleum ether, stirring for 30 minutes, filtering and collecting separated solid which is 180.6g of 3-chloro-4-bromobenzoic acid (II), wherein the yield is about 76.7%, the content is higher than 95% through HPLC (high performance liquid chromatography) detection, and the solid can be directly used for the next reaction without further purification.
Example 3
The procedure is otherwise the same as in example 1, except that 3-chloro-4-bromobenzoic acid (II) is prepared as follows:
p-bromobenzoic acid (201 g, 1.0 mol), anhydrous aluminum trichloride (147g, 1.1mol) and 1,1, 2-trichloroethane (1500g) were charged to a reactor equipped with stirring and heating means. Cooling to 0 ℃ after uniform stirring, introducing chlorine (78.1 g, 1.1mol), heating to 80 ℃, continuing to stir for 10 hours, cooling to room temperature after the reaction is finished, filtering to remove insoluble substances, distilling under reduced pressure to remove most of solvent, adding obtained residue into petroleum ether, stirring for 30 minutes, filtering and collecting separated solid which is 192.5g of 3-chloro-4-bromobenzoic acid (II), wherein the yield is about 81.7%, the content is higher than 95% through HPLC (high performance liquid chromatography) detection, and the solid can be directly used for the next reaction without further purification.
Example 4
The procedure was otherwise the same as in example 1, except that 2-nitro-4-bromo-5-chlorobenzoic acid (III) was prepared as follows:
adding 3-chloro-4-bromobenzoic acid (II) (235.5 g, 1.0 mol) and concentrated sulfuric acid (1200 g) into a reactor, uniformly stirring, cooling to 0-5 ℃, then dropwise adding a concentrated sulfuric acid solution (760 g) of HNO3 with the mass fraction of 10%, keeping the temperature of the mixture at 0-5 ℃ in the dropwise adding process, continuously stirring for 30 minutes after the dropwise adding is finished, removing the ice bath, naturally heating to room temperature, then heating to 50 ℃, continuously stirring for reaction for 6 hours, slowly pouring the mixture into a large amount of ice water after the reaction is finished, controlling the temperature within 30 ℃, filtering and collecting separated solids after stirring for 30 minutes, wherein the separated solids are 203.6g of 2-nitro-4-bromo-5-chlorobenzoic acid (III), the yield is about 72.6%, the content is higher than 95% by HPLC (high performance liquid chromatography), and the solids can be directly used for the next reaction without further purification.
A small amount of crude product is taken to be refined by methanol and then detected, 1 HNMR(DMSO,400 MHz):8.27(s,1H),8.74(s,1H)。FAB-MS(m/z)::281.5 (M+H)。
example 5
The procedure was otherwise the same as in example 1, except that 2-nitro-4-bromo-5-chlorobenzoic acid (III) was prepared as follows:
adding 3-chloro-4-bromobenzoic acid (II) (235.5 g, 1.0 mol) and concentrated sulfuric acid (1300 g) into a reactor, uniformly stirring, cooling to 0-5 ℃, then dropwise adding concentrated sulfuric acid solution (790 g) of HNO3 with the mass fraction of 10%, keeping the temperature of the mixture at 0-5 ℃ in the dropwise adding process, continuously stirring for 30 minutes after the dropwise adding is finished, removing the ice bath, naturally heating to room temperature, then heating to 50 ℃, continuously stirring for reaction for 8 hours, slowly pouring the mixture into a large amount of ice water after the reaction is finished, controlling the temperature within 30 ℃, filtering and collecting separated solid after stirring for 30 minutes, wherein the solid is 216.8g of 2-nitro-4-bromo-5-chlorobenzoic acid (III), the yield is about 77.3%, the content is higher than 95% by HPLC (high performance liquid chromatography), and the solid can be directly used for the next reaction without further purification.
A small amount of crude product is taken to be refined by methanol and then detected, 1 HNMR(DMSO,400 MHz):8.27(s,1H),8.74(s,1H)。FAB-MS(m/z)::281.5 (M+H)。
example 6
The procedure was otherwise the same as in example 1 except that 2-amino-4-bromo-5-chlorobenzoic acid (I) in step C was prepared as follows:
adding 2-nitro-4-bromo-5-chlorobenzoic acid (III) (280.5 g, 1.0 mol), ferric chloride (6 g), 50% hydrazine hydrate solution (100 g) and deionized water (850 g) into a reactor, stirring at room temperature for 6 hours, adjusting the pH to 12 with 5% sodium hydroxide solution after the reaction is finished, filtering to remove insoluble substances, adjusting the pH of filtrate to 7 with 10% glacial acetic acid, stirring for 30 minutes, filtering and collecting precipitated solid which is 211.2g of 2-amino-4-bromo-5-chlorobenzoic acid (I), wherein the yield is about 84.3%, the content is higher than 95% through HPLC (high performance liquid chromatography), and the product can be directly used for the subsequent reaction step of preparing halofuginone without further purification. The crude product is recrystallized by a methanol-water mixed solution to obtain a refined product of the 2-amino-4-bromo-5-chlorobenzoic acid (I).
1 HNMR(DMSO,400 MHz):7.07(s,1H),7.79(s,1H)。FAB-MS(m/z)::251.5 (M+H)。
Example 7
The 2-amino-4-bromo-5-chlorobenzoic acid (I) was prepared by the same procedure as in example 1 except for the C step:
adding 2-nitro-4-bromo-5-chlorobenzoic acid (III) (280.5 g, 1.0 mol), ferric chloride (9 g), 50% hydrazine hydrate solution (130 g) and deionized water (1200 g) into a reactor, stirring at room temperature for reaction for 9 hours, adjusting the pH to 12 with 5% sodium hydroxide solution after the reaction is finished, filtering to remove insoluble substances, adjusting the pH of the filtrate to 7 with 10% glacial acetic acid, stirring for 30 minutes, filtering and collecting separated solid which is 218.9g of 2-amino-4-bromo-5-chlorobenzoic acid (I), wherein the yield is about 87.4%, the content is higher than 95% by HPLC (high performance liquid chromatography), and the solid can be directly used for the subsequent reaction step of preparing halofuginone without further purification. The crude product is recrystallized by a methanol-water mixed solution to obtain a refined product of the 2-amino-4-bromo-5-chlorobenzoic acid (I).
1 HNMR(DMSO,400 MHz):7.07(s,1H),7.79(s,1H)。FAB-MS(m/z)::251.5 (M+H)。
Example 8
The procedure was otherwise the same as in example 1 except that 2-amino-4-bromo-5-chlorobenzoic acid (I) in step C was prepared as follows:
adding 2-nitro-4-bromo-5-chlorobenzoic acid (III) (280.5 g, 1.0 mol), ferric chloride (10 g), 50% hydrazine hydrate solution (140 g) and deionized water (1250 g) into a reactor, stirring at room temperature for 10 hours, adjusting the pH to 12 with 5% sodium hydroxide solution after the reaction is finished, filtering to remove insoluble substances, adjusting the pH of the filtrate to 7 with 10% glacial acetic acid, stirring for 30 minutes, filtering to collect precipitated solid, namely 226.3g of 2-amino-4-bromo-5-chlorobenzoic acid (I), wherein the yield is about 90.3%, the content is higher than 95% by HPLC (high performance liquid chromatography), and the subsequent reaction step of preparing halofuginone can be directly carried out without further purification. The crude product is recrystallized by a methanol-water mixed solution to obtain a refined product of the 2-amino-4-bromo-5-chlorobenzoic acid (I).
1 HNMR(DMSO,400 MHz):7.07(s,1H),7.79(s,1H)。FAB-MS(m/z)::251.5 (M+H)。
Although the invention has been described and illustrated in some detail by the inventor, it should be understood that modifications and/or alterations to the above-described embodiments, or equivalent alterations thereto, will become apparent to those skilled in the art without departing from the spirit of the invention, and that no limitation to the invention is intended by the terms of the present invention as set forth herein is intended to be exhaustive or understood.

Claims (1)

1. A method for preparing a halofuginone intermediate 2-amino-4-bromo-5-chlorobenzoic acid is characterized by comprising the following steps: the halofuginone intermediate 2-amino-4-bromo-5-chlorobenzoic acid represented by formula (I) is obtained as follows:
Figure FDA0003688617270000011
preparation of 3-chloro-4-bromobenzoic acid (II)
Adding 1 weight part of p-bromobenzoic acid, 0.73-0.74 weight part of anhydrous aluminum trichloride and 5-10 weight parts of 1,1, 2-trichloroethane into a reactor with a stirring and heating device, uniformly stirring, cooling to 0 ℃, introducing 0.35-0.43 weight part of chlorine, heating to 80 ℃, continuously stirring for reacting for 8-12 hours, cooling to room temperature after the reaction is finished, filtering to remove insoluble substances, distilling under reduced pressure to remove most of solvent, adding the obtained residue into petroleum ether, stirring for 30 minutes, filtering and collecting precipitated solid which is a crude product of 3-chloro-4-bromobenzoic acid (II), detecting the content by HPLC to be more than 95%, and directly using the crude product in the next reaction without further purification;
b.preparation of 2-nitro-4-bromo-5-chlorobenzoic acid (III)
Adding 1 time of 3-chloro-4-bromobenzoic acid (II) and 5-6 parts by weight of concentrated sulfuric acid into a reactor, uniformly stirring, cooling to 0-5 ℃, and then dropwise adding 10% by mass of HNO 3 3.23-3.52 parts of concentrated sulfuric acid solution, keeping the temperature of the mixture at 0-5 ℃ in the dropwise adding process, continuously stirring for 30 minutes after the dropwise adding is finished, removing the ice bath, naturally heating to room temperature, then heating to 50 ℃, continuously stirring for reacting for 6-10 hours, slowly pouring the mixture into a large amount of ice water after the reaction is finished, controlling the temperature within 30 ℃, stirring for 30 minutes, filtering and collecting precipitated solid which is a 2-nitro-4-bromo-5-chlorobenzoic acid (III) crude product, detecting the content by HPLC (high performance liquid chromatography) to be more than 95%, and directly using the crude product for the next reaction without further purification;
preparation of C.2-amino-4-bromo-5-chlorobenzoic acid (I)
Adding 1 weight part of 2-nitro-4-bromo-5-chlorobenzoic acid (III), 0.02-0.05 weight part of ferric chloride, 0.35-0.55 weight part of hydrazine hydrate solution with the mass fraction of 50% and 3-6 weight parts of deionized water into a reactor, and then stirring and reacting for 6-12 hours at room temperature, adjusting the pH value to 12 by using a 5% sodium hydroxide solution after the reaction is finished, filtering to remove insoluble substances, adjusting the pH value of filtrate to 7 by using 10% glacial acetic acid, stirring for 30 minutes, filtering and collecting precipitated solid to obtain a crude product of the 2-amino-4-bromo-5-chlorobenzoic acid (I), detecting the content of the crude product to be more than 95% by HPLC (high performance liquid chromatography), directly using the crude product in a subsequent reaction step for preparing halofuginone without further purification, and recrystallizing the crude product by using a methanol-water mixed solution to obtain a refined product of the 2-amino-4-bromo-5-chlorobenzoic acid (I).
CN201910982668.3A 2019-10-16 2019-10-16 Method for preparing halofuginone intermediate 2-amino-4-bromo-5-chlorobenzoic acid Active CN110759831B (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1651428A (en) * 2004-02-06 2005-08-10 上海因诺生化科技有限公司 Preparation method of hydrobromic acid antifebrile dichroanone
CN101219977A (en) * 2008-01-25 2008-07-16 延边大学 CLT acid production method without acid waste liquid discharge
CN101835752A (en) * 2007-08-31 2010-09-15 阿斯利康(瑞典)有限公司 Heterocyclic amides useful for the treatment of cancer and psoriasis
CN104326992A (en) * 2014-10-15 2015-02-04 浙江省诸暨合力化学对外贸易有限公司 Method for synthesizing difluoro methyl triazoline-ketone and sulfentrazone
WO2017090756A1 (en) * 2015-11-27 2017-06-01 大鵬薬品工業株式会社 Novel biphenyl compound or salt thereof

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1651428A (en) * 2004-02-06 2005-08-10 上海因诺生化科技有限公司 Preparation method of hydrobromic acid antifebrile dichroanone
CN101835752A (en) * 2007-08-31 2010-09-15 阿斯利康(瑞典)有限公司 Heterocyclic amides useful for the treatment of cancer and psoriasis
CN101219977A (en) * 2008-01-25 2008-07-16 延边大学 CLT acid production method without acid waste liquid discharge
CN104326992A (en) * 2014-10-15 2015-02-04 浙江省诸暨合力化学对外贸易有限公司 Method for synthesizing difluoro methyl triazoline-ketone and sulfentrazone
WO2017090756A1 (en) * 2015-11-27 2017-06-01 大鵬薬品工業株式会社 Novel biphenyl compound or salt thereof

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Denomination of invention: Method for preparing the intermediate 2-amino-4-bromo-5-chlorobenzoic acid of Changshan ketone

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