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Preparation method of alpha-alkenyl boronic acid pinacol esters

A technology of alkenyl boronic acid and alcohol borate, which is applied in the field of preparation of α-alkenyl boronic acid pinacol ester, can solve the problems of difficulty in obtaining, low yield, long reaction time, etc., and achieve the effect of simple operation

Inactive Publication Date: 2013-04-03
DALIAN NETCHEM CHIRAL TECH
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  • Summary
  • Abstract
  • Description
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AI Technical Summary

Problems solved by technology

This method has the following disadvantages: (1) The market sources of certain raw material alkenyl halides are less, especially in large quantities, and it is more diff

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0020] A method for preparing α-alkenylboronic acid pinacol ester, isopropenylboronic acid pinacol ester as an example

[0021] Preparation of p-toluenesulfonylacetone hydrazone:

[0022] Add 111.74g p-toluenesulfonylhydrazide (0.60mol, 1eq), 38.28g acetone (0.66mol, 1.1eq), 523mL absolute ethanol to a 1L single bottle with magnetic stirring, heat to reflux for 3 hours, cool to room temperature, filter , and dried to obtain 116.80 g of p-toluenesulfonylacetone hydrazone as a white solid, with a yield of 86.02%.

[0023] Preparation of isopropenylboronic acid pinacol ester:

[0024] Under the protection of nitrogen, the system was cooled to -40°C with a dry ice / ethanol external bath, and 100 mL of n-butyl lithium in n-hexane (2.5 mol / L, 1.00 mol, 4 eq) was added to a 1 L four-necked flask with mechanical stirring. Add 142mL of n-hexane dropwise to a solution of 56.57g of p-toluenesulfonylacetone hydrazone (0.25mol, 1eq) dissolved in 29.05g of tetramethylethylenediamine (1.00m...

Embodiment 2

[0026] A method for preparing α-alkenylboronic acid pinacol ester, isopropenylboronic acid pinacol ester is an example:

[0027] Under the protection of nitrogen, the system was cooled to -50°C with a dry ice / ethanol external bath, and 120 mL of n-butyl lithium in n-hexane (2.5 mol / L, 1.20 mol, 4 eq) was added to a 1 L four-necked flask with mechanical stirring. Add 170mL of n-hexane dropwise to the solution of 67.88g of p-toluenesulfonylacetone hydrazone (0.30mol, 1eq) dissolved in 34.86g of tetramethylethylenediamine (1.20mol, 4eq) in the dropping funnel, after dropping, naturally appreciate and keep warm at room temperature 3 hours. Continue to cool down to below -40°C, add 111.60g of isopropyl pinacol borate (0.60mol, 2eq) dropwise, after dropping, keep warm for 1 hour, naturally rise to room temperature and stir overnight, then add 3% hydrochloric acid dropwise at 0-10°C When the pH value of the solution is 6-7, separate layers, extract the aqueous layer once with 150mL ...

Embodiment 3

[0029] A method for preparing α-alkenylboronic acid pinacol ester, vinylboronic acid pinacol ester is an example

[0030] Preparation of p-toluenesulfonyl acetaldehyde hydrazone:

[0031] Add 93.12g of p-toluenesulfonylhydrazide (0.50mol, 1eq), 24.23g of acetaldehyde (0.55mol, 1.1eq), and 436mL of absolute ethanol to a 1L single bottle with magnetic stirring, heat to reflux for 3 hours, and cool down to room temperature. Filter and dry to obtain 90.93 g of p-toluenesulfonyl acetaldehyde hydrazone as a white solid, with a yield of 85.49%.

[0032] Preparation of vinyl borate pinacol ester:

[0033] Under the protection of nitrogen, the system was cooled to -70°C with a dry ice / ethanol external bath, and 104 mL of n-butyl lithium in n-hexane (2.5 mol / L, 1.04 mol, 4 eq) was added to a 1 L four-necked flask with mechanical stirring. Add 143mL of n-hexane dropwise to a solution of 55.19g of p-toluenesulfonylacetaldehyde hydrazone (0.26mol, 1eq) dissolved in 30.21g of tetramethyle...

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Abstract

The invention discloses a preparation method of alpha-alkenyl boronic acid pinacol esters. The preparation method comprises the following steps of: firstly, carrying out backflow on a ketone compound with alpha hydrogen atoms and p-toluenesulfonhydrazide in an absolute ethyl alcohol solvent so as to obtain p-toluenesulfonylhydrazone; and secondly, carrying out Shapiro reaction on the p-toluenesulfonylhydrazone, butyl lithium and tetramethylethylenediamine, adding boronic acid pinacol ester compounds into obtained solution, adjusting the pH value of the solution to be 6-7, adding an organic solvent into the solution for extraction, and carrying out reduced pressure distillation on the concentrated solvent in which a polymerization inhibitor is added, thereby obtaining the alpha-alkenyl boronic acid pinacol esters. The method disclosed by the invention has the innovations that the application of a raw material, namely alkenyl halide, which is uneasy to obtain in documents is avoided, but the cheap and easily available ketone compound with alpha hydrogen atoms is taken as a starting material and is reacted with the p-toluenesulfonhydrazide to generate the p-toluenesulfonylhydrazone, then the p-toluenesulfonylhydrazone is subjected to the Shapiro reaction with the butyl lithium and the tetramethylethylenediamine to obtain alkenyl negative ions with nucleophilicity, and the alkenyl negative ions are reacted with boronic acid pinacol esters to obtain the alpha-alkenyl boronic acid pinacol esters. The method disclosed by the invention is convenient to operate; and the alpha-alkenyl boronic acid pinacol esters with high yield are prepared by the cheap and easily available starting material.

Description

technical field [0001] The invention relates to the technical field of chemical synthesis, in particular to a method for preparing α-alkenylboronic acid pinacol ester. Background technique [0002] Currently known methods for synthesizing α-alkenylboronic acid pinacol esters, the synthetic method of bibliographical reports generally adopts alkenyl halides as raw materials to prepare Grignard reagents, then react with borate esters to prepare alkenylboronic acids, and then It can be synthesized by reacting with pinacol, and the total reaction yield is about 40%. This method has the following disadvantages: (1) Some raw material alkenyl halides have less market sources, especially for large quantities, which are more difficult to obtain. (2) The preparation of alkenyl halides into Grignard reagents is not easy to trigger, the reaction time is long, easy to deteriorate, and the yield is low. Contents of the invention [0003] The purpose of the present invention is to solve...

Claims

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Application Information

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IPC IPC(8): C07F5/04
Inventor 刘启宾刘经红
Owner DALIAN NETCHEM CHIRAL TECH
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