1. A synthetic method of N-bromomethylphthalimide is disclosed, wherein the molecular structural formula of the compound is as follows:

，

the method is characterized in that N-hydroxymethyl phthalimide and phosphorus tribromide are subjected to bromination reaction in an inert solvent to prepare N-bromomethylphthalimide;

the reaction equation of the synthesis method is as follows:

。

2. the method for synthesizing N-bromomethylphthalimide according to claim 1, wherein the molar ratio of N-hydroxymethylphthalimide to phosphorus tribromide is 3: (1-1.1).

3. The method for synthesizing N-bromomethylphthalimide according to claim 1, wherein the inert solvent is benzene, toluene or xylene. The mass of the solvent is 5-10 times of that of the N-hydroxymethyl phthalimide.

4. The method for synthesizing N-bromomethylphthalimide according to claim 1, wherein the reaction temperature is 80-150 ℃ and the reaction time is 1-3 hours.

Background

N-bromomethylphthalimide, the molecular structural formula is:

。

n-bromomethylphthalimide, also known as N-bromomethylphthalimide. The molecular structure contains active bromine atoms, so that nucleophilic substitution reaction can be carried out on the active bromine atoms and a plurality of groups, and various substituted methylamine compounds can be obtained by removing PHT protective groups, so that the N-bromomethylphthalimide is an important organic synthesis intermediate and is widely applied to organic synthesis in industries such as medicine, pesticide, dye and the like.

The prior published synthesis method of N-bromomethylphthalimide is to heat and reflux N-hydroxymethylphthalimide in a large amount of acetic acid solution of hydrogen bromide to prepare the product. The process generates a large amount of acetic acid solution waste liquid of hydrogen bromide, and the production cost is high; the wastewater treatment difficulty is high, and the pollution is serious. In addition, the acetic acid has large volatility and strong acidity, the VOCS of the acetic acid is difficult to control in the production process, and the labor and occupational health conditions of operators are low. The traditional process does not meet the requirements of the modern clean production process.

Disclosure of Invention

The invention aims to provide a synthesis method of N-bromomethylphthalimide, which adopts N-hydroxymethyl phthalimide to perform bromination reaction with phosphorus tribromide in an inert solvent to prepare the N-bromomethylphthalimide. After the reaction is finished, the by-product phosphorous acid is removed by layering, and the phosphorous acid is sold as a by-product. And crystallizing the N-bromomethylphthalimide from the solvent, and filtering to obtain the N-bromomethylphthalimide. The filtrate can be circularly used for the next batch of production without treatment, the process realizes zero emission, and represents the sustainable development direction of clean production.

The invention aims to realize the synthesis method of N-bromomethylphthalimide by the following technical scheme, and the molecular structural formula of the compound is as follows:

，

the synthesis method is characterized in that N-hydroxymethyl phthalimide and phosphorus tribromide are subjected to bromination reaction in an inert solvent to prepare the N-bromomethylphthalimide. After the reaction is finished, filtering and drying to obtain the N-bromomethylphthalimide with the purity of more than 98 percent. The highest molar yield can reach more than 96%. The filtered mother liquor is directly used for the next batch of feeding.

Compared with the prior art, the invention has the following beneficial effects: the invention can completely react with equimolar or slightly excessive phosphorus tribromide, replaces the traditional hydrogen bromide acetic acid solution with the phosphorus tribromide, greatly improves the utilization rate of bromine atoms of raw materials, reduces the discharge of three wastes caused by the excessive hydrogen bromide acetic acid solution, also stops the discharge of VOCS (volatile organic compounds) generated by the hydrogen bromide acetic acid solution, and improves the occupational health level. The production efficiency is improved, and the production cost is reduced. Each batch of mother liquor is directly used for feeding the next batch, and the byproduct phosphorous acid is sold as a byproduct, so that zero discharge of the process is realized.

Detailed Description

The invention is further illustrated by the following examples of embodiments.

A synthetic method of N-bromomethylphthalimide is disclosed, wherein the molecular structural formula of the compound is as follows:

，

the synthesis method is characterized in that N-hydroxymethyl phthalimide and phosphorus tribromide are subjected to bromination reaction in an inert solvent to prepare the N-bromomethylphthalimide.

Further, the molar ratio of N-hydroxymethylphthalimide to phosphorus tribromide is 3: (1-1.1).

Further, the inert solvent is benzene, toluene or xylene. The mass of the solvent is 5-10 times of that of the N-hydroxymethyl phthalimide.

Furthermore, the reaction temperature is 80-150 ℃, and the reaction time is 1-3 hours.

The reaction equation is as follows:

。

during the specific operation, firstly, the metered N-hydroxymethyl phthalimide and the solvent are put into a reactor, phosphorus tribromide is slowly dripped, after the dripping is finished, the mixture is stirred and heated to reflux, the reaction is kept at the temperature for a period of time, the hot reaction is layered, phosphorous acid is removed, then the mixture is cooled to room temperature, the mixture is discharged and filtered, the next batch of feed is used for feeding the filtrate, and the filter cake is dried to obtain the finished product.

Example 1

30g (0.17mol) of N-hydroxymethylphthalimide and 150g of benzene are added into a 500ml four-neck flask which is provided with a mechanical stirring, dropping funnel, thermometer, reflux condenser, ice-water bath and electric heating jacket, the stirring is started, and the temperature is reduced by the ice-water bath.

When the temperature is reduced to below 10 ℃, 16g (0.059mol) of phosphorus tribromide is dripped into the bottle from a constant-pressure dripping funnel, and the dripping speed is controlled to ensure that the temperature of the materials in the bottle does not exceed 10 ℃. After the dropwise addition, the temperature was raised and the mixture was refluxed. When the temperature of the system materials rises to 80 ℃, the lower end of the reflux condenser is refluxed with liquid drops. The temperature was maintained at this temperature for 3 hours. Removing the electric heating jacket, and stopping stirring. Naturally cooling to 60 deg.C, separating the materials in the bottle into upper and lower layers, removing lower layer phosphorous acid, stirring again, and cooling to 0 deg.C.

At this time, a large amount of white flaky crystals precipitated in the flask. Filtration and drying of the filter cake gave 23.6g of white flaky crystalline powder. The liquid chromatography content was 96.07%, based on N-hydroxymethylphthalimide, the molar yield was 57.84%.

Example 2

30g (0.17mol) of N-hydroxymethylphthalimide and 300g of toluene are added into a 500ml four-neck flask which is provided with a mechanical stirring, dropping funnel, thermometer, reflux condenser, ice-water bath and electric heating jacket, the stirring is started, and the temperature is reduced by the ice-water bath.

When the temperature is reduced to below 10 ℃, 16g (0.059mol) of phosphorus tribromide is dripped into the bottle from a constant-pressure dripping funnel, and the dripping speed is controlled to ensure that the temperature of the materials in the bottle does not exceed 10 ℃. After the dropwise addition, the temperature was raised and the mixture was refluxed. When the temperature of the system materials rises to 110 ℃, the lower end of the reflux condenser is refluxed with liquid drops. The temperature was maintained at this temperature for 3 hours. Removing the electric heating jacket, and stopping stirring. Naturally cooling to 90 deg.C, separating the materials in the bottle into upper and lower layers, removing lower layer phosphorous acid, stirring, and cooling to 0 deg.C.

At this time, a large amount of white flaky crystals precipitated in the flask. Filtration and drying of the filter cake gave 37.5g of white flaky crystalline powder. The content of liquid chromatography was 98.85%, and the molar yield based on N-hydroxymethylphthalimide was 91.91%.

The filtrate is ready for use.

Example 3

30g (0.17mol) of N-hydroxymethylphthalimide and 300g of dimethylbenzene are added into a 500ml four-neck flask which is provided with a mechanical stirring, dropping funnel, thermometer, reflux condenser, ice-water bath and electric heating jacket, the stirring is started, and the temperature is reduced by the ice-water bath.

When the temperature is reduced to below 10 ℃, 16g (0.059mol) of phosphorus tribromide is dripped into the bottle from a constant-pressure dripping funnel, and the dripping speed is controlled to ensure that the temperature of the materials in the bottle does not exceed 10 ℃. After the dropwise addition, the temperature was raised and the mixture was refluxed. When the temperature of the system material rises to 135 ℃, the lower end of the reflux condenser is refluxed with liquid drops. The temperature was maintained at this temperature for 3 hours. Removing the electric heating jacket, and stopping stirring. Naturally cooling to 110 deg.C, separating the materials in the bottle into upper and lower layers, removing lower layer phosphorous acid, stirring again, and cooling to 0 deg.C.

At this time, a large amount of white flaky crystals precipitated in the flask. Filtration and drying of the filter cake gave 32g of white flaky crystalline powder. The liquid chromatography content was 99.93%, based on N-hydroxymethylphthalimide, with a molar yield of 78.43%.

Example 4

30g (0.17mol) of N-hydroxymethylphthalimide, the filtrate of example 2 (235.8 g), were placed in a 500ml four-necked flask equipped with mechanical stirring, a dropping funnel, a thermometer, a reflux condenser, an ice-water bath and an electric mantle, and the stirring was turned on and the temperature was lowered in the ice-water bath.

When the temperature is reduced to below 10 ℃, 16g (0.059mol) of phosphorus tribromide is dripped into the bottle from a constant-pressure dripping funnel, and the dripping speed is controlled to ensure that the temperature of the materials in the bottle does not exceed 10 ℃. After the dropwise addition, the temperature was raised and the mixture was refluxed. When the temperature of the system materials rises to 110 ℃, the lower end of the reflux condenser is refluxed with liquid drops. The temperature was maintained at this temperature for 3 hours. Removing the electric heating jacket, and stopping stirring. Naturally cooling to 90 deg.C, separating the materials in the bottle into upper and lower layers, removing lower layer phosphorous acid, stirring, and cooling to 0 deg.C.

At this time, a large amount of white flaky crystals precipitated in the flask. Filtration and drying of the filter cake gave 40.3g of white flaky crystalline powder. The content of liquid chromatography was 98.50%, and the molar yield based on N-hydroxymethylphthalimide was 98.77%.