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Preparation method of 3-fluorophthalic acid

A technology of fluorophthalonitrile and fluorobenzonitrile, which is applied in the field of preparing 3-fluorophthalic acid, and can solve the problems of low yield of target product, low purity of target product, and difficult preparation

Inactive Publication Date: 2009-03-11
EAST CHINA UNIV OF SCI & TECH
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Problems solved by technology

[0005] The defect that exists in the above-mentioned prior art is: starting material (3-fluorophthalic anhydride, 1-fluoronaphthalene or 1-fluoro-2,3-xylene) is difficult to prepare; Target product (3-fluorophthalic anhydride) Diformic acid) yield is low (up to no more than 50%); the preparation time is too long (only one-step reaction takes 96 hours) or the purity of the target product is not high

Method used

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  • Preparation method of 3-fluorophthalic acid

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[0015] The method for preparing 3-fluorophthalic acid (structure shown in formula A) of the present invention comprises the following steps:

[0016] 1. With 2,6-difluorobenzonitrile as starting raw material, in aprotic solvent, 2,6-difluorobenzonitrile is carried out ammoniation reaction (reaction with ammonia gas), reacts at least four hours, obtains 2- Amino, 6-fluorobenzonitrile.

[0017] Wherein: the reaction temperature of said ammoniation reaction should be set to 100 DEG C~130 DEG C (100 DEG C~110 DEG C of more preferred reaction temperature); Said aprotic solvent can be selected from sulfolane, dimethyl sulfoxide, N, One, two or more mixtures of N-dimethylacetamide or N,N-dimethylformamide; the amount of said aprotic solvent is the starting material (2,6-difluorobenzonitrile) 2 to 14 times the weight.

[0018] II. First carry out the diazotization reaction of 2-amino and 6-fluorobenzonitrile, that is, under the condition of 50°C to 70°C (the best temperature is 60°C...

Embodiment

[0026] I. Ammonification:

[0027] Add 200g (1.439mol) 2,6-difluorobenzonitrile and 600mL dimethyl sulfoxide into a 5L three-necked flask equipped with a spherical condenser, a thermometer, and an electric stirrer, and pass ammonia gas at room temperature for 30 minutes (pass ammonia gas at room temperature When the reaction bottle was a milky white turbid liquid), the temperature was raised to 100 ° C ~ 110 ° C under the condition of continuing to pass the ammonia gas, and the reaction was stopped after 4 hours. The dripped liquid was transparent, and then about 1400-1500 mL of water was added to the reaction bottle, the solid was precipitated by cooling, filtered, and washed with water to obtain 140 g of 2-amino-6-fluoro-benzonitrile, yield: 71.5%, content: 98%. Melting point: 128~130℃.

[0028] 1 H NMR (acetone-d 6 )δ (ppm): 5.82 (br s, 2H, NH 2 ); 6.35-7.48 (m, 3H, Ph).

[0029] 19 F NMR (CD 3 SOCD 3 , CFCl 3 ), δ (ppm): 108.8.

[0030] II. Diazotization and brom...

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Abstract

The invention relates to a preparation method for 3-fluorophthalic acid. The preparation method comprises the following steps that: (I) 2,6-difluorobenzonitrile which is used as a starting material is subjected to an ammoximation reaction in an aprotic solvent to obtain 2-amino,6 -fluorobenzonitrile; (II) the 2-amino,6 -fluorobenzonitrile is subjected to a diazotization reaction and then reacts with liquid HBr to form 2- bromo,6 -fluorobenzonitrile; (III) the 2- bromo,6 -fluorobenzonitrile is subjected to a cyanation reaction in an aprotic solvent to form 3-fluorophthalic benzenedicarbonitrile; (IV) the 3-fluorophthalic benzenedicarbonitrile is decomposed in an aqueous solution of inorganic acid to obtain a target substance. The preparation method overcomes the defects of difficult preparation of raw materials, low yield of the target substance, long preparation time or / and low purity and so on in the prior art of preparing the 3-fluorophthalic acid and is capable of meeting commercial preparation requirements.

Description

technical field [0001] The invention relates to a method for preparing 3-fluorophthalic acid. Background technique [0002] 3-Fluorophthalic acid (structure shown in formula A) is a kind of widely used chemical industry and pharmaceutical intermediate, as can be used for preparing the third generation quinolone antibacterial drug (J.Med.Chem., 1995,38, 4478). [0003] [0004] So far, the reported method for preparing 3-fluorophthalic acid is mainly to use 1-fluoronaphthalene or 1-fluoro-2,3-xylene as starting raw material, through oxidation (such as potassium permanganate or RuO 2 ·H 2 O / NaClO oxidation) to obtain the target compound (Canadian Journal of Chemistry, 58 (23), 2084, 1980; Journal of Organic Chemistry, 52 (1), 129, 1987 and Journal of Organic Chemistry, 39 (16), 2468, 1974) . [0005] The defect that exists in the above-mentioned prior art is: starting material (3-fluorophthalic anhydride, 1-fluoronaphthalene or 1-fluoro-2,3-xylene) is difficult to prepa...

Claims

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Application Information

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IPC IPC(8): C07C63/72C07C51/08
Inventor 钱旭红陈卫东曹松孙华君
Owner EAST CHINA UNIV OF SCI & TECH
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