The way to preparation of 2,4-Difluorobenzoic acid

2,4-Difluorobenzoic acid is a kind of white to light yellow crystal powders with Molecular Formula: C7H4F2O2 and Molecular Weight: 158.1. It is soluble in water, stable at room temperature in closed containers under normal storage and handling conditions. We should store it in a tightly closed container. Store it in a cool, dry, well-ventilated area away from incompatible substances. The CAS Registry Number is 1583-58-0.

This invention relates to a method for the preparation of 2,4-Difluorobenzoic acid. It has been prepared by the oxidation of the corresponding toluene derivative. More particularly, this invention relates to a process for the preparation of 2,4-Difluorobenzoic acid by the decarboxylation of 4,5,-difluorophthalic anhydride or 4,5-difluorophthalic acid in which the decarboxylation reaction is conducted in N-methylpyrrolidone or dimethyl acetamide. Copper catalysts may be used in this reaction.

2,4-Difluorobenzoic acid(CAS NO: 1583-58-0)  is a useful chemical intermediate.  For example, it has been used as an intermediate in the preparation of potential anti-cancer agents. In addition, it has been used in the synthesis of antidepressant drugs. Attempts were made to prepare 2,4-Difluorobenzoic acid by decarboxylation of 4,5-difluorophthalic anhydride. It may be readily prepared by the reaction of 4,5-dichlorophthalic anhydride with potassium fluoride as disclosed in U.S. Pat. No. 4,374,266 . The acid may be readily prepared by reacting the anhydride with water.

The decarboxylation of 4,5-difluorophthalic anhydride proved to be difficult, since previously known methods of decarboxylation led to a low yield of the desired product along with numerous by-products. The following chart illustrates the decarboxylation methods which were tested. The percentage product shown in the results were those obtained by gas chromatographic analysis, DFBA stands for 2,4-Difluorobenzoic acid s.m. stands for starting material.

The difluorobenzoic acid may be isolated from the reaction mixture by acidifying the mixture and extracting with a suitable solvent such as ethyl acetate or diethyl ether. Evaporation of the solvent yields crude difluorobenzoic acid which may be recrystallized/decolorized by using water and activated carbon.

We have found that 4,5-difluorophthalic anhydride and 4,5-difluorophthalic acid may be decarboxylated in high yield to 2,4-Difluorobenzoic acid in N-methyl-2-pyrrolidone or dimethyl acetamide using copper, copper oxide, copper salts, or halides and salts of Zn, Cd, Ag and Ni as a catalyst.

Surprisingly, we have found that 4,5-difluorophthalic anhydride and 4,5-difluorophthalic acid may be selectively decarboxylated in N-methyl-pyrrolidone, dimethyl acetamide or quinoline to yield 2,4-Difluorobenzoic acid.

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What is 2,4-Dichloropyridine used for?

2,4-Dichloropyridine is a very useful intermediates, mainly used in pharmaceutical and pesticide synthesis. Some of these products have been used for household chemicals and crops, individual product market prospects.

Synthesis of 2,4-Dichloropyridine(CAS NO: 26452-80-2) began in 1891. In more than one century, a number of new synthetic methods have developed. From the raw materials used can be grouped into three categories: (1) pyridine derivatives chloride; (2) the direct chlorination of pyridine; (3) Other.

Ours is a large population and a large agricultural country, a vast potential market for pharmaceuticals and pesticides, concerns the progress in these two areas has important practical significance. This article will briefly describe 2,4-Dichloropyridine in medicine and agriculture purposes

1.   2,4-Dichloropyridine used in synthetic drugs

The chlorine atomic in 2,4-Dichloropyridine can be substituted by a nucleophile, such as a phenyl acetonitrile, and 2 - chloropyridine-pyridyl of a strong base (Pyridylation), then alkylation, hydrolysis and decarboxylation, to produce anti-histamines - non-Nepalese December Ming. Antiarrhythmic drug - disopyramide can also be produced similarly.

2,4-Dichloropyridine oxidized to give 2 - chloro-pyridine nitrogen oxides, which, after reaction with sodium hydrosulfide was pyrithione. Zinc pyrithione as fungicides, mainly used in shampoos. 2 - chloro-pyridine is synthesized mold pyrithione net (2-mercaptopyridine N-oxide sodium), preservatives, and other intermediates.

2.   2,4-Dichloropyridine used for synthetic pesticides

The nitrogen oxides of 2,4-Dichloropyridine through nitrification to give 2 - chloro-4 - nitro pyridine, after reduction to give 2 - chloro-4 - aminopyridine, which is preparing Forchlorfenuron essential intermediate body.

Forchlorfenuron is a new class of high activity, low toxicity, broad-spectrum plant growth regulator, with cell division activity, its mechanism and purine cytokinins (kinetin, zeatin) the same, but more active than they are high 10 ~ 100 times. Practice has proved that Forchlorfenuron for many species of plants have very far-reaching effects, flowery front with time, can induce parthenocarpy into seedless fruit, increase crop fruit set; flowering or after flowering, when used to increase the fruit, thus significantly increased crop yield and fruit quality, has been used in food crops, melons, fruits, vegetables, some crops and ornamental plants.

2,4-Dichloropyridine further chlorination can be obtained in a high yield of 2,6 - dichloro-pyridine and various polychlorinated pyridine substituted. 2,6 - dichloro-pyridine used to take antibiotics (enoxalin); nitrogen stabilizer tetrachloro grass and (Nitrapyrin); 2,3,5,6 - tetrachloropyridine itself with herbicidal properties, it is made insecticide chlorpyrifos and chlorine grass and herbicide b (triclopyr) intermediates; 2,3,5 - trichloro-pyridine is pesticide intermediates.

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