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Preparation method of 2, 4-difluoro-3-nitrobenzoic acid
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A technology of nitrobenzoic acid and difluorobenzoic acid, which is applied in the field of medicine and can solve the problems of high cost, low selectivity, and low yield
Active Publication Date: 2020-06-26
江苏恒沛药物科技有限公司 +1
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[0018] This preparation method requires the use of a specially prepared catalyst, and iodide must be used as a starting material, which has problems such as high cost, low selectivity and low yield.
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Embodiment 1
[0114] Step 1: Synthesis of 2,6-difluoroacetamidobenzene (5)
[0115] Add 100g (0.77mol) of 2,6-difluoroaniline and 600mL of toluene to the reaction flask, add 87g (0.85mol) of acetic anhydride dropwise at a temperature of 0-20°C under stirring, keep the reaction for 4 hours after the addition, and cool down to 0 Keep stirring at -10°C for 1 hour, filter, and dry the solid under reduced pressure to obtain 125 g of 2,6-difluoroacetamidobenzene (5), with a yield of 94%.
[0116] Step 2: Synthesis of 3-bromo-2,6-difluoroacetamidobenzene (4)
[0117] Add 55g (0.32mol) of 2,6-difluoroacetamidobenzene and 660g of concentrated sulfuric acid into the reaction flask, and stir until the system is completely dissolved. At 20-40°C, add 63g (0.35mol) NBS in portions, and keep stirring for 5h after the addition.
[0118] After the reaction is qualified, the reaction solution is slowly poured into 1000 g of ice water, stirred to precipitate a white solid. The crude product of 3-bromo-2,6-...
Embodiment 2
[0130] Synthesis of 2,6-difluoroacetamidobenzene (5)
[0131] Operate according to step 1 of Example 1, except that the reaction solvents are respectively toluene, acetic acid, methylenechloride and hexane, and other operating conditions are the same.
[0132] The yield of 2,6-difluoroacetamidobenzene (5) and the data of different solvents are shown in Table 1.
[0136] Synthesis of 2,6-difluoroacetamidobenzene (5).
[0137] The operation was carried out according to step 1 of Example 1, except that the reaction temperatures were 0-20° C., 20-40° C. and 60-80° C., and other operating conditions were the same. See Table 2 for the yield of 2,6-difluoroacetamidobenzene (5) and data at different temperatures.
[0138] Table 2
[0139] Reaction temperature (°C) Reaction time (h) Reaction yield% 0-20 4 94 20-40 4 92 60-80 4 88
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Abstract
The invention discloses a preparation method of 2, 4-difluoro-3-nitrobenzoic acid. The preparation method comprises the following technical key points of: carrying out amino protection on 2, 6-difluoroaniline to obtain a compound V; reacting the compound V with a halogenating reagent in a solvent to obtain a compound IV; reacting the compound IV with carbon monoxide in the presence of a palladiumcatalyst to obtain a compound III or a compound III'; hydrolyzing the compound III or the compound III' to remove a protective group from amino, and hydrolyzing the generated carboxylic ester or amideto obtain a compound II; and finally, oxidizing the compound II to obtain a compound I. The invention aims to provide a preparation method of 2, 4-difluoro-3-nitrobenzoic acid, and large-scale industrial production of 2, 4-difluoro-3-nitrobenzoic acid can be realized.
Description
technical field [0001] The invention relates to a preparation method of 2,4-difluoro-3-nitrobenzoic acid, which belongs to the field of medical technology (organic synthesis). Background technique [0002] 2,4-difluoro-3-nitrobenzoic acid, CAS registration number: 1425174-31-7, English name is: 2,4-difluoro-3-nitrobenzoic acid. [0003] The structural formula is as follows: [0004] [0005] The structure of 2,4-difluoro-3-nitrobenzoic acid contains two fluorine atoms, a nitro group and a carboxyl group, which can be used to construct the molecular structure of new drugs and is a novel pharmaceutical synthesis intermediate. [0006] 2,4-Difluoro-3-nitrobenzoic acid can be used to synthesize drug candidate compounds, for example: HEPAAREGENIX GMBH+PCT Int.Appl.(2019), WO 2019243315A1[DE]Tricyclicproteinkinase inhibitors for promoting liver regeneration or reducing or Preventing hepatocyte death, screening and testing drugs with good biological activity, such as the fol...
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