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A kind of method for preparing methyl boric acid

A technology of methyl boric acid and boric acid ester, which is applied in the field of preparation of methyl boric acid, can solve the problems of production safety hazards, difficult extraction, waste of solvents, etc., and achieve the effects of simplified operation, easy acquisition, and convenient operation

Active Publication Date: 2016-09-28
CANGZHOU PURUI DONGFANG SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] At present, there are two main methods for synthesizing methylboronic acid. One is to hydrolyze borane and carbon monoxide to obtain methylboronic acid. In this method, borane is a flammable gas, and carbon monoxide is very dangerous once it leaks due to its strong toxicity.
The other is methyl boronic acid which is hydrolyzed after the reaction of methyl Grignard reagent with special unstable boron chloride reagent, in which trimethyl boron will inevitably be produced as a by-product, and trimethyl boron is very active in nature, and it is easy to Spontaneous combustion occurs with air, which brings safety hazards to production. Secondly, methyl boric acid is very water-soluble, and it is not easy to extract in aqueous solution, wasting a lot of solvent

Method used

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  • A kind of method for preparing methyl boric acid
  • A kind of method for preparing methyl boric acid

Examples

Experimental program
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Effect test

Embodiment 1

[0022] Synthesis of (trimethylsilyl)methylboronic acid: Under nitrogen protection, add metal magnesium (0.33 moles) and a few small grains of iodine to a reaction flask equipped with a condenser tube and a constant pressure feeding funnel, and add trimethylsilyl dropwise under stirring. 30 ml of a mixed solution of methyl bromide (0.3 mol) dissolved in 250 ml of 2-methyltetrahydrofuran. Heat to above 40°C, and slowly add the remaining solution dropwise after the reaction is initiated. The temperature was raised to reflux for 3 hours, and the temperature was lowered to room temperature. In another reaction flask, under the protection of nitrogen, add trimethyl borate (0.35 mol) and 80 ml of 2-methyltetrahydrofuran, stir evenly, cool down to -20°C, and slowly add the Grignard reagent prepared above, 2 After adding -3 hours, keep warm and continue to react for 2-2.5 hours. When it is confirmed that the reaction does not change, raise the temperature to 0°C and add 10% hydrochlor...

Embodiment 2

[0028] Synthesis of (dimethyl tert-butylsilyl) methylboronic acid: under nitrogen protection, add metal magnesium (0.40 moles) and a few small grains of iodine to a reaction flask equipped with a condenser tube and a constant-pressure feeding funnel, and add two drops of iodine under stirring. 30 ml of a mixed solution of methyl tert-butylsilyl bromide (0.4 mol) dissolved in 250 ml of 2-methyltetrahydrofuran. Heat to above 50°C, and slowly add the remaining solution dropwise after the reaction is initiated. The temperature was raised to reflux for 3 hours, and the temperature was lowered to room temperature. In another reaction flask, under the protection of nitrogen, add trimethyl borate (0.33 mol) and 100 ml of 2-methyltetrahydrofuran, stir evenly, cool down to -20°C, and slowly add the Grignard reagent prepared above, 2 After adding -3 hours, keep warm and continue to react for 2-2.5 hours. When it is confirmed that the reaction does not change, raise the temperature to 0°...

Embodiment 3

[0034] Synthesis of (trimethylsilyl)methylboronic acid: Under nitrogen protection, add metal magnesium (0.33 moles) and a few small grains of iodine to a reaction flask equipped with a condenser tube and a constant pressure feeding funnel, and add trimethylsilyl dropwise under stirring. 30 ml of a mixed solution of methyl bromide (0.3 mol) dissolved in 350 ml of 2-methyltetrahydrofuran. Heat to above 40°C, and slowly add the remaining solution dropwise after the reaction is initiated. The temperature was raised to reflux for 3 hours, and the temperature was lowered to room temperature. In another reaction flask, under the protection of nitrogen, add triisopropyl borate (0.33 moles) and 180 ml of 2-methyltetrahydrofuran, stir evenly, cool down to -10°C, and slowly add the Grignard reagent prepared above, After 2-3 hours of addition, keep warm and continue to react for 2-2.5 hours. When it is confirmed that the reaction does not change, raise the temperature to 0°C, add 10% hyd...

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Abstract

The invention discloses a method for preparing methyl boric acid. The method includes the steps that silica-base-protected methyl bromide and magnesium react in 2-methyl tetrahydrofuran to generate a Grignard reagent, boric acid ester is added in at low temperature, and after the reaction is finished, silicane-protected methyl boric acid is obtained through hydrochloric acid hydrolysis; an intermediate continues to react with tetra-n-butyl ammonium fluoride to remove silica bases, and then methyl boric acid tripolymer is distilled out. After being added into water, the tripolymer can be hydrolyzed into the methyl boric acid through stirring at the room temperature. The synthetic method is simple and reliable, it is avoided that potential safety hazards are amplified, the separation problem of the water-soluble methyl boric acid is solved, the purity of the obtained methyl boric acid can reach over 98%, and a new way is provided for producing the methyl boric acid in an amplified mode.

Description

technical field [0001] The invention relates to a method for preparing methylboronic acid, which belongs to the field of synthesis of fine chemical intermediates. Background technique [0002] Catalytic asymmetric reduction is an important way to obtain chiral compounds. As the most classic catalyst for reducing carbonyl compounds: the combination of MeCBS and borane is used to prepare chiral alcohols. This method is still used today due to its high enantioselectivity. in wide use. As one of the most important reagents, the synthesis of methylboronic acid still lacks an effective method. [0003] At present, there are two main methods for synthesizing methylboronic acid. One is to react borane with carbon monoxide and then hydrolyze it to obtain methylboronic acid. In this method, borane is a flammable gas, and carbon monoxide is very dangerous once leaked due to its strong toxicity. The other is methyl boronic acid which is hydrolyzed after the reaction of methyl Grignard...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07F5/02
CPCC07F5/025
Inventor 冷延国桂迁张世红
Owner CANGZHOU PURUI DONGFANG SCI & TECH
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