Preparation method of 2-amino-5-fluorobenzoic acid

Abstract

The preparation method of 2-amino-5-fluobenzoic acid uses 4-fluoroaniline as raw material, and includes the following steps: making said raw material and hydrated chloral and oxammonium hydrochloride implement condensation reaction to obtain N-(4-fluorophenyl)-2-(hydroxyimide) acetamide, then making cyclization in concentrated sulfuric acid to produce 5-fluoro-1H-indole-2,3-diketone, and finally, under the alkaline condition using oxydol to make oxidation so as to obtain the invented 2-amino-5-fluorobenzoic acid.

Description

technical field [0001] The present invention relates to an improved process for the preparation of 2-amino-5-fluorobenzoic acid. Background technique [0002] 2-Amino-5-fluorobenzoic acid is a very important precursor for the synthesis of drugs, herbicides, plant growth regulators and quinoline fungicides. Specifically, it can be used as the precursor of the virus-killing agent of HIV infectious disease; as the precursor of the anti-viral agent of herpes virus; the preparation of phyllophylline and its analogues are used as hypoglycemic agents for the treatment of diabetes; the preparation of aminoquinone Phylin as an anticancer agent; preparation of triazine and its analogs for local ischemia, hypoglycemia, cerebral vasospasm, Alzheimer's disease, Parkinson's disease, Huntington's chorea, atrophy neuroprotective agents in schizophrenia, myelopathy, and schizophrenia. [0003] Many methods for the preparation of 2-amino-5-fluorobenzoic acid have been reported in the existi...

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Problems solved by technology

[0012] This method undergoes a process of first reduction and then oxidation. Within a certain temperature range, the speed of the reduction reaction usually increases with the increase of temperature, but too high a temperature may cause coking of organic matter, making the color of aniline darker. It also accelerates the carbon deposition process on the surface of the catalyst; while the oxidation of potassium permanganate is generally carried out under alkaline or neutral conditions, but due to the presence of amino groups on the aromatic ring and the generation of strong acids, the alkalinity of the reaction solution decreases. leading to a decrease in the reaction yield

Another factor is that the raw material 2-methyl-4-fluoronitrobenzene is not easy to obtain, the price is relatively high, and multiple recrystallizations are required in the whole process, resulting in a decrease in yield

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