阅读说明：本技术 一种苏糖醇基聚氨酯的合成方法 (Synthetic method of threitol-based polyurethane ) 是由 刘双良 胡稳 杨皓然 梁会会 叶长春 赵卫华 周立明 方少明 于 2021-08-12 设计创作，主要内容包括：本发明涉及一种苏糖醇基聚氨酯的合成方法,以L-(+)-酒石酸二甲酯为原料,乙酸乙酯为溶剂,在BF-(3)·Et-(2)O催化下与二甲氧基甲烷发生反应,得到缩醛产物,经LiAlH-(4)还原合成缩醛化苏糖醇,将缩醛化苏糖醇与丁二酸酐作用使其开环,形成双酯键并得到相应的二羧酸,二羧酸经酰氯化-叠氮化-Curtius重排得到二异氰酸酯,二异氰酸酯与缩醛化苏糖醇聚合得苏糖醇基聚氨酯。本发明合成的聚氨酯结构灵活可修饰,后期可进行材料的改性。(The invention relates to a synthesis method of threitol-based polyurethane, which takes L- (+) -tartaric acid dimethyl ester as a raw material and ethyl acetate as a solvent to prepare the threitol-based polyurethane in BF 3 ·Et 2 Reacting with dimethoxymethane under the catalysis of O to obtain acetal product, and reacting with LiAlH 4 Reducing and synthesizing acetalation threitol, reacting the acetalation threitol with succinic anhydride to open a ring, forming a diester bond and obtaining corresponding dicarboxylic acid, carrying out acyl chlorination-azido-Curtius rearrangement on the dicarboxylic acid to obtain diisocyanate, and polymerizing the diisocyanate and the acetalation threitol to obtain threitol-based polyurethane. The polyurethane structure synthesized by the inventionFlexible and can be modified, and the material can be modified in the later period.)

1. A synthetic method of threitol based diisocyanate is characterized by comprising the following steps: taking L- (+) -dimethyl tartrate as a raw material and ethyl acetate as a solvent in BF₃·Et₂Reacting with dimethoxymethane under the catalysis of O to obtain an acetal product 1; product 1 is subjected to LiAlH₄Reducing and synthesizing acetalized threitol, namely a product 2; reacting the acetalized threitol with succinic anhydride to open the ring of the acetalized threitol to form a diester bond and obtain corresponding dicarboxylic acid, namely a product 3; performing acyl chlorination-azide-Curtius rearrangement on dicarboxylic acid to obtain a product 4, a product 5 and a product 6, namely threitol diisocyanate;

the product 1 is: (4R,5R) -1,3-dioxolane-4, 5-dicarboxylic acid methyl ester;

the product 2 is: ((4S,5S) -1,3-dioxolane-4,5-diyl) dimethanol;

the product 3 is: 4,4' - (((((4S, 5S) -1, 3-dioxolan-4, 5-diyl) bis (methylene)) bis (oxy)) bis (4-oxobutanoic acid);

the product 4 is: ((4R,5R) -1, 3-dioxolan-4, 5-diyl) bis (methylene) bis (4-chloro-4-oxobutanoic acid);

the product 5 is: ((4R,5R) -1, 3-dioxolan-4, 5-diyl) bis (methylene) bis (4-azido-4-oxobutanoic acid);

the product 6 is: ((4R,5R) -1,3-dioxolane-4,5-diyl) bis (methylene) bis (3-isocyanate).

2. The method of synthesis according to claim 1, comprising the steps of:

(1) 56.2mmol of L- (+) -dimethyl tartrate, 100mL of ethyl acetate, 67mmol of dimethoxymethane and 140mmol of BF₃·Et₂Adding O into a 250mL flask, and uniformly stirring; refluxing for 7-12 h at 65-80 ℃, cooling the reaction to room temperature, and reacting with saturated NaHCO₃Quenching the solution for reaction, transferring the system to a separating funnel, layering, and keeping an organic phase; washing an organic phase by using 30mL of water and 30mL of saturated NaCl solution in sequence, and finally drying the organic phase by using anhydrous sodium sulfate, filtering and concentrating to obtain a product 1 which is directly used for the next reaction;

(2) dissolving 32.6mmol of product 1 in 50mL of diethyl ether at 0 ℃ under the nitrogen atmosphere, dropwise and slowly adding 84mL of 1mol/L lithium aluminum hydride solution with stirring, wherein the solvent is tetrahydrofuran, and reacting at room temperature for 12 h; placing the reaction system in an ice bath for cooling, and slowly adding 7mL of water, 8mL of 15% (w/w) sodium hydroxide solution and 25mL of water in sequence under stirring to generate a large amount of white precipitate after reaction; the precipitate was filtered off and washed with hot acetone; mixing the filtrates, concentrating, drying with anhydrous sodium sulfate, filtering, and concentrating; separating by column chromatography to obtain a product 2;

(3) uniformly mixing 11.6mmol of product 2 and 26.6mmol of succinic anhydride, and reacting at 120 ℃ for 24 hours to obtain orange oil; separating the orange oily substance by column chromatography to obtain a product 3;

(4) 5.00mmol of product 3 were added to 5mL of SOCl at 0 deg.C₂Then adding 0.05mmol of DMF into the system and stirring for 30 minutes; continuing to react for 1.5h, concentrating the mixture under reduced pressure, and recovering excessive thionyl chloride to obtain a crude product 4 which is directly used for the next reaction;

(5) dissolving 4.96mmol of crude product 4 in 12.5mL of toluene at 0 ℃, and then dropwise adding the solution into 10mL of aqueous solution of sodium azide, wherein the dosage of the sodium azide is 25.1mmol, and controlling the dropwise adding speed to ensure that the reaction temperature is not more than 5 ℃; after 20 minutes of reaction, the system was transferred to a separatory funnel, separated into two phases and the aqueous phase was discarded; washing the organic phase with 10% (w/w) potassium carbonate solution, water and saturated NaCl solution, drying with anhydrous sodium sulfate, and filtering to obtain toluene solution of product 5;

(6) and (3) dropwise adding the toluene solution of the product 5 obtained in the step (5) into 5mL of toluene at 110V, controlling the reaction temperature to be not lower than 100 ℃, observing that gas is continuously formed, continuously reacting for 15 minutes after dropwise adding, concentrating the mixture, and draining the solvent by an oil pump to obtain a product 6.

3. The synthesis method according to claim 2, wherein the developing solvent used in the column chromatography in the step (2) is dichloromethane-methanol (v/v) 50: 1-20: 1.

4. The synthesis method according to claim 2, wherein the developing solvent used in the column chromatography in step (3) is dichloromethane-ethyl acetate (v/v) -8: 1-1: 1.

5. The synthesis method according to any one of claims 2 to 3, wherein the synthesis method of step (1) is further characterized by: weighing 0.168mol of L- (+) dimethyl tartrate and 0.333mol of paraformaldehyde, adding into a 250mL flask, and uniformly stirring; then, 40mL of 98% (wt) concentrated sulfuric acid is added into the system drop by drop, and the reaction is carried out for 8-24 h at 60 ℃ after the concentrated sulfuric acid is completely dissolved; after the reaction is cooled to room temperature, extracting the system with dichloromethane for 8-10 times, and combining organic phases; and drying the obtained organic phase by using anhydrous sodium sulfate, and separating a product 1 by using a column chromatography, wherein a developing agent is petroleum ether and ethyl acetate (v/v) is 10: 1-5: 1.

6. A method for synthesizing threitol-based polyurethane, characterized in that the product 6 threitol-based diisocyanate obtained in claim 1 and the product 2 acetalized threitol are polymerized to obtain threitol-based polyurethane, namely a product 7, wherein the product 7 is: amino ((4S,5S) -5- (((3-acetamidopropionyl) oxy) methyl) -1, 3-dioxolan-4-yl) methyl-3- (((((4S, 5S) -5- (methoxymethyl) -1, 3-dioxolan-4-yl) methoxy) carbonyl) propanoate.

7. The synthesis method of claim 6, which is characterized by comprising the following steps: in N₂Adding 5mL of DMMF and 2.00mmol of product 2 into a 50mL flask under the atmosphere, and uniformly stirring at room temperature; then adding 2.00mmol of the product 6 and 2% (w/w) of dibutyltin dilaurate catalyst, and reacting for 48h at 120 ℃; after the reaction was completed, the mixture was dropped into 50mL of methanol to precipitate, and the product 7 was obtained by filtration.

Technical Field

The invention relates to a synthetic method of threitol-based polyurethane, belonging to the field of high polymer materials.

Background

Environmental pollution caused by the exhaustibility of petroleum resources and the low degradability of oil-based polymers has increased interest in synthesizing polymers using natural renewable resources. Among them, carbohydrates are ideal raw materials. They can be produced in large quantities by plants and microorganisms, and can even be derived from agricultural waste, belonging to renewable resources; and, can provide functional groups suitable for the synthesis of polycondensates, such as hydroxyl and carboxyl groups, and have stereochemical diversity; in addition, polymers prepared from carbohydrates tend to have high degradability.

In the past decades, many groups have been working on the synthesis of monomers from naturally available sugars and on this basis producing structurally novel degradable polymers. Compared with the classical polymer, the polymer prepared from glycosyl monomer is harmless to human health, and the hydrophilicity of the polymer ensures the larger hydrolytic degradability of the polymer and reduces the influence on the environment. Therefore, it is an excellent method for preparing novel biodegradable and biocompatible materials, which can be applied to the fields of biomedicine and food packaging.

Polyurethanes (PU) are generally produced by the polymerization of diisocyanates and poly (di) polyols and are widely used materials in many fields. In particular, polyurethanes have good biocompatibility, including low platelet adhesion and in vitro protein adsorption properties, and these unique properties have made them increasingly useful in medicine. However, the polyurethane synthesized by using the conventional raw materials has hydrolytic stability, thereby preventing the application of the polyurethane in the biomedical field. Increasing the hydrolytic degradability of PU by introducing hydrophilic sugar units into the polyurethane chain is a common and effective solution, but current reports focus on the use of sugars as poly (di) polyols, and less research on sugar-derived diisocyanates.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a synthetic method of threitol-based polyurethane.

In order to achieve the purpose, the invention adopts the technical scheme that:

a synthetic method of threitol-based diisocyanate comprises the following steps: taking L- (+) -dimethyl tartrate as a raw material and ethyl acetate as a solvent in BF₃·Et₂Reacting with dimethoxymethane under the catalysis of O to obtain an acetal product 1; product 1 is subjected to LiAlH₄Reducing and synthesizing acetalized threitol, namely a product 2; reacting the acetalized threitol with succinic anhydride to open the ring of the acetalized threitol to form a diester bond and obtain corresponding dicarboxylic acid, namely a product 3; performing acyl chlorination-azide-Curtius rearrangement on dicarboxylic acid to obtain a product 4, a product 5 and a product 6, namely threitol diisocyanate;

the product 1 is: (4R,5R) -1,3-dioxolane-4, 5-dicarboxylic acid methyl ester;

the product 2 is: ((4S,5S) -1,3-dioxolane-4,5-diyl) dimethanol;

the product 3 is: 4,4' - (((((4S, 5S) -1, 3-dioxolan-4, 5-diyl) bis (methylene)) bis (oxy)) bis (4-oxobutanoic acid);

the product 4 is: ((4R,5R) -1, 3-dioxolan-4, 5-diyl) bis (methylene) bis (4-chloro-4-oxobutanoic acid);

the product 5 is: ((4R,5R) -1, 3-dioxolan-4, 5-diyl) bis (methylene) bis (4-azido-4-oxobutanoic acid);

the product 6 is: ((4R,5R) -1,3-dioxolane-4,5-diyl) bis (methylene) bis (3-isocyanate).

The synthesis method comprises the following steps:

(1) 56.2mmol of L- (+) -dimethyl tartrate, 100mL of ethyl acetate, 67mmol of dimethoxymethane and 140mmol of BF₃·Et₂O is added into a 250mL flask and stirred evenlyHomogenizing; refluxing for 7-12 h at 65-80 ℃, cooling the reaction to room temperature, and reacting with saturated NaHCO₃Quenching the solution for reaction, transferring the system to a separating funnel, layering, and keeping an organic phase; washing an organic phase by using 30mL of water and 30mL of saturated NaCl solution in sequence, and finally drying the organic phase by using anhydrous sodium sulfate, filtering and concentrating to obtain a product 1 which is directly used for the next reaction;

(2) dissolving 32.6mmol of product 1 in 50mL of diethyl ether at 0 ℃ under the nitrogen atmosphere, dropwise and slowly adding 84mL of 1mol/L lithium aluminum hydride solution with stirring, wherein the solvent is tetrahydrofuran, and reacting at room temperature for 12 h; placing the reaction system in an ice bath for cooling, and slowly adding 7mL of water, 8mL of 15% (w/w) sodium hydroxide solution and 25mL of water in sequence under stirring to generate a large amount of white precipitate after reaction; the precipitate was filtered off and washed with hot acetone; mixing the filtrates, concentrating, drying with anhydrous sodium sulfate, filtering, and concentrating; separating by column chromatography to obtain a product 2;

(3) uniformly mixing 11.6mmol of product 2 and 26.6mmol of succinic anhydride, and reacting at 120 ℃ for 24 hours to obtain orange oil; separating the orange oily substance by column chromatography to obtain a product 3;

(4) 5.00mmol of product 3 were added to 5mL of SOCl at 0 deg.C₂Then adding 0.05mmol of DMF into the system and stirring for 30 minutes; continuing to react for 1.5h, concentrating the mixture under reduced pressure, and recovering excessive thionyl chloride to obtain a crude product 4 which is directly used for the next reaction;

(5) dissolving 4.96mmol of crude product 4 in 12.5mL of toluene at 0 ℃, and then dropwise adding the solution into 10mL of aqueous solution of sodium azide, wherein the dosage of the sodium azide is 25.1mmol, and controlling the dropwise adding speed to ensure that the reaction temperature is not more than 5 ℃; after 20 minutes of reaction, the system was transferred to a separatory funnel, separated into two phases and the aqueous phase was discarded; washing the organic phase with 10% (w/w) potassium carbonate solution, water and saturated NaCl solution, drying with anhydrous sodium sulfate, and filtering to obtain toluene solution of product 5;

(6) and (3) dropwise adding the toluene solution of the product 5 obtained in the step (5) into 5mL of toluene at the temperature of 110 ℃, controlling the reaction temperature to be not lower than 100 ℃, observing that gas is continuously formed, continuously reacting for 15 minutes after dropwise adding, concentrating the mixture, and pumping out the solvent by an oil pump to obtain a product 6.

The developing solvent used in the column chromatography in the step (2) is dichloromethane and methanol (v/v) which are 50: 1-20: 1.

The developing solvent used in the column chromatography in the step (3) is dichloromethane-ethyl acetate (v/v) 8: 1-1: 1.

The synthesis method in the step (1) can also comprise the following steps: weighing 0.168mol of L- (+) dimethyl tartrate and 0.333mol of paraformaldehyde, adding into a 250mL flask, and uniformly stirring; then, 40mL of 98% (wt) concentrated sulfuric acid is added into the system drop by drop, and the reaction is carried out for 8-24 h at 60 ℃ after the concentrated sulfuric acid is completely dissolved; after the reaction is cooled to room temperature, extracting the system with dichloromethane for 8-10 times, and combining organic phases; and drying the obtained organic phase by using anhydrous sodium sulfate, and separating a product 1 by using a column chromatography, wherein a developing agent is petroleum ether and ethyl acetate (v/v) is 10: 1-5: 1.

A synthetic method of threitol-based polyurethane is to polymerize an obtained product 6 threitol-based diisocyanate and a product 2 acetalized threitol to obtain threitol-based polyurethane, namely a product 7, wherein the product 7 is: amino ((4S,5S) -5- (((3-acetamidopropionyl) oxy) methyl) -1, 3-dioxolan-4-yl) methyl-3- (((((4S, 5S) -5- (methoxymethyl) -1, 3-dioxolan-4-yl) methoxy) carbonyl) propanoate.

The specific method comprises the following steps: in N₂Adding 5mL of DMMF and 2.00mmol of product 2 into a 50mL flask under the atmosphere, and uniformly stirring at room temperature; then adding 2.00mmol of the product 6 and 2% (w/w) of dibutyltin dilaurate catalyst, and reacting for 48h at 120 ℃; after the reaction was completed, the mixture was dropped into 50mL of methanol to precipitate, and the product 7 was obtained by filtration.

The synthesis flow of threitol based polyurethanes is as follows:

wherein, the product 1 is: dimethyl (4R,5R) -1,3-dioxolane-4,5-dicarboxylate ];

(4R,5R) -1,3-dioxolane-4, 5-dicarboxylic acid methyl ester;

the product 2 is: ((4S,5S) -1,3-dioxolane-4,5-diyl) dimethane;

((4S,5S) -1,3-dioxolane-4,5-diyl) dimethanol;

the product 3 is: 4,4' - ((((4S,5S) -1, 3-dionolane-4, 5-diyl) bis (methylene)) bis (oxy)) bis (4-oxobutanic acid); 4,4' - (((((4S, 5S) -1, 3-dioxolan-4, 5-diyl) bis (methylene)) bis (oxy)) bis (4-oxobutanoic acid);

the product 4 is:

((4R,5R) -1,3-dioxolane-4,5-diyl) bis (methyl) bis (4-chloro-4-oxobutanoate); ((4R,5R) -1, 3-dioxolan-4, 5-diyl) bis (methylene) bis (4-chloro-4-oxobutanoic acid);

the product 5 is:

((4R,5R)-1,3-dioxolane-4,5-diyl)bis(methylene)bis(4-azido-4-oxobutanoate)；

((4R,5R) -1, 3-dioxolan-4, 5-diyl) bis (methylene) bis (4-azido-4-oxobutanoic acid);

the product 6 is:

((4R,5R) -1,3-dioxolane-4,5-diyl) bis (methyl) bis (3-isocyanatopropanoate); ((4R,5R) -1,3-dioxolane-4,5-diyl) bis (methylene) bis (3-isocyanate);

the product 7 is:

((4S,5S)-5-(((3-acetamidopropanoyl)oxy)methyl)-1,3-dioxolan-4-yl)methyl3-(((4S,5S)-5-(methoxy methyl)-1,3-dioxolan-4-yl)methoxy)carbonyl)amino)propanoate；

amino ((4S,5S) -5- (((3-acetamidopropionyl) oxy) methyl) -1, 3-dioxolan-4-yl) methyl-3- (((((4S, 5S) -5- (methoxymethyl) -1, 3-dioxolan-4-yl) methoxy) carbonyl) propanoate.

The reaction process and mechanism of each step are as follows:

1. using L- (+) dimethyl tartrate as initial material and ethyl acetate as solvent in BF₃·Et₂Reacting with dimethoxymethane under the catalysis of O to form acetal;

2. ester group via LiAlH₄Reducing to alcohol;

3. nucleophilic ring opening of succinic anhydride by alcohol to obtain dicarboxylic acid;

4. dicarboxylic acids and SOCl₂Reacting to generate acyl chloride;

5. acid chloride treatment with NaN₃Nucleophilic substitution to generate acyl azide;

6. heating acyl azide to generate Curtius rearrangement to obtain diisocyanate containing a threitol skeleton;

7. and polymerizing the diisocyanate and the threitol to obtain the novel threitol-based polyurethane.

The invention has the beneficial effects that:

1. the carbon source for synthesizing the polyurethane is completely from biomass raw materials, is green, rich and nontoxic, and is expected to be applied to medical materials. Wherein Threitol (Threitol, 2418-52-2) is a four-carbon sugar alcohol, and is diastereoisomer of erythritol. From an economic and synthetic perspective, the acetalized threitol for use in the present invention is synthesized from dimethyl L- (+) -tartrate by an aldolisation reaction and ester group reduction. And the L- (+) -tartaric acid dimethyl ester is derived from L- (+) -tartaric acid, which is a widely used beverage additive and a raw material for pharmaceutical industry and is one of the main organic acids in wine.

2. The invention leads acetalized threitol to react with succinic anhydride to open the ring, form diester bond and obtain corresponding dicarboxylic acid. The dicarboxylic acid is subjected to acyl chlorination-azide-Curtius rearrangement to obtain the diisocyanate. And polymerizing the diisocyanate and the acetalized threitol to obtain the threitol-based polyurethane. Under the action of an acid solution, acetal segments in the polyurethane are hydrolyzed, and two free hydroxyl groups can be introduced into a PU repeating unit, so that the property of the polyurethane is changed, and the degradation of the material is facilitated.

3. The invention adopts BF₃·Et₂The product 1 is synthesized by an O catalytic method, and the reaction raw materials and the catalyst are cheap. The reaction system is concentrated after liquid separation and washing, and a high-purity product 1 can be directly obtained. Compared with the common concentrated sulfuric acid catalytic method, the method has the advantages of simple and convenient operation, simple post-treatment, high product yield and contribution to large-scale production.

4. The invention adopts column chromatography to separate the product 2 from the product 3, thereby avoiding the defect that the product is easy to deteriorate by vacuum distillation. Wherein, the column chromatography is utilized to separate out the pure product 2 and the pure product 3, which is beneficial to obtaining the high-purity product 6 in the subsequent reaction. The prior similar method is to directly carry out subsequent reaction on the unpurified product 2 and the unpurified product 3, and when the product 6 is subjected to reduced pressure distillation and purification, higher temperature is needed, so that the product 6 is easily damaged.

5. The polyurethane synthesized by the invention has flexible and modifiable structure, and can be modified in the later stage.

Drawings

FIG. 1 is a representation of the NMR spectrum of product 1;

wherein the content of the first and second substances,¹HNMR(300MHz,CDCl₃):δ＝5.27(s,2H)，4.78(s,2H)，3.84(s,6H)；

FIG. 2 is a representation of the NMR spectrum of product 2;

wherein the content of the first and second substances,¹HNMR(300MHz,CDCl₃):δ＝5.06(s,2H)，4.00-3.92.(m,2H)，3.86-3.70(m,4H)，2.31 (s,2H)；

FIG. 3 is a representation of the NMR spectrum of product 3;

wherein the content of the first and second substances,¹HNMR(300MHz,CDCl₃):δ＝8.20(s,2H)，5.04(s,2H)，4.32-4.22(m,4H)，4.09-3.97(m, 2H)，2.68(s,8H)；

FIG. 4 is a representation of the NMR spectrum of product 6;

wherein the content of the first and second substances,¹HNMR(300MHz,CDCl₃):δ＝5.05(s,2H)，4.35-4.20(m,4H)，4.09-3.99(m,2H)，3.62 (t,J＝6.3Hz,4H)，2.67(t,J＝6.3Hz,4H)；

FIG. 5 is a representation of the NMR spectrum of product 7;

wherein the content of the first and second substances,¹H NMR(300MHz,CDCl₃):δ＝5.60(br,2H)，5.09-4.95(m,4H)，4.34-4.13(m,8H)， 4.09-3.92(m,4H)，3.51-3.39(m,4H)，2.64-2.56(m,4H)。

FIG. 6 is a graph of high resolution mass spectrometry (ESI-HRMS) characterization of product 6;

wherein M/z is [ M + Na]⁺:351.07802。

Detailed Description

The following examples further illustrate the embodiments of the present invention in detail.

Example 1 Synthesis of threitol based diisocyanate

A synthetic method of threitol-based diisocyanate comprises the following steps:

(1) 10g (56.2mmol) of L- (+) -tartaric acid dimethyl ester, 100mL of Ethyl Acetate (EA), 6.0mL (67mmol) of dimethoxymethane and 17.8mL (140mmol) of BF were added₃·Et₂Adding O (boron trifluoride diethyl etherate) into a 250mL flask, and uniformly stirring; refluxing for 7-12 h at 65-80 ℃, cooling the reaction to room temperature, and reacting with saturated NaHCO₃Quenching the solution for reaction, transferring the system to a separating funnel, layering, and keeping an organic phase; washing the organic phase with 30mL of water and 30mL of saturated NaCl solution in sequence, and finally, washing the organic phase with anhydrousDrying with sodium sulfate, filtering, and concentrating to obtain product 1(9.17g), with yield of 85.8%, which can be directly used in the next reaction;

(2) dissolving 6.19g (32.6mmol) of the product 1 in 50mL of diethyl ether at 0 ℃ under a nitrogen atmosphere, dropwise and slowly adding 84mL of 1mol/L lithium aluminum hydride solution (tetrahydrofuran as a solvent) while stirring, and reacting at room temperature for 12 h; placing the reaction system in an ice bath for cooling, and slowly adding 7mL of water, 8mL of 15% (w/w) sodium hydroxide solution and 25mL of water to generate a large amount of white precipitate; filtering out the precipitate, and washing the precipitate with hot acetone; mixing the filtrates, concentrating, and drying with anhydrous sodium sulfate; filtering and concentrating; separating the product 2(3.43g) by column chromatography, wherein the developing solvent is dichloromethane and methanol (v/v) is 50: 1-20: 1, and the yield is 78.4%;

(3) 1.56g (11.6mmol) of product 2 and 2.68g (26.6mmol) of succinic anhydride are mixed uniformly and reacted at 120 ℃ for 24h to obtain an orange oil; separating the orange oily substance by using a column chromatography method to obtain a product 3(3.58g), wherein a developing agent is dichloromethane and ethyl acetate (v/v) is 8: 1-5: 1, and the yield is 92.3%;

(4) 1.67g (5.00mmol) of product 3 are added to 5mL SOCl at 0 deg.C₂Then, 3.9. mu.L (0.05mmol) of DMF was added to the system and stirred for 30 minutes; continuing to react for 1.5h, concentrating the mixture under reduced pressure, and recovering excessive thionyl chloride to obtain a crude product 4 which is directly used for the next reaction;

(5) at 0 ℃, 1.84g (4.96mmol) of the crude product 4 is dissolved in 12.5mL of toluene and then is dropwise added into 1.63 g (25.1mmol) of sodium azide aqueous solution, and the dropping rate is controlled so that the temperature in the reaction does not exceed 5 ℃; after 20 minutes of reaction, the system was transferred to a separatory funnel, separated into two phases and the aqueous phase was discarded; washing the organic phase with 10% (w/w) potassium carbonate solution, water and saturated NaCl solution, drying with anhydrous sodium sulfate, and filtering to obtain toluene solution of product 5;

(6) dropwise adding the toluene solution of the product 5 into 5mL of toluene at 110 ℃, controlling the reaction temperature to be not lower than 100 ℃, and observing continuous formation of gas during the reaction; after the reaction was continued for 15 minutes after the completion of the dropwise addition, the mixture was concentrated, and the solvent was drained off by an oil pump to obtain a pale yellow product 6(1.15 g); the overall yield of product 6 from product 3 was 70.1%.

Example 2 Synthesis of threitol based diisocyanate

A synthetic method of threitol-based diisocyanate comprises the following steps:

(1) weighing (30g, 0.168mol) L- (+) dimethyl tartrate and (30g, 0.333mol) paraformaldehyde, adding into a 250mL flask, and uniformly stirring; then, 40mL of 98% (wt) concentrated sulfuric acid is added into the system drop by drop, and the reaction is carried out for 8-24 h at 60 ℃ after the concentrated sulfuric acid is completely dissolved; after the reaction is cooled to room temperature, extracting the system with dichloromethane for 8-10 times, and combining organic phases; drying the obtained organic phase by using anhydrous sodium sulfate, and separating a product 1 by using a column chromatography method, wherein a developing agent is petroleum ether and ethyl acetate (v/v) is 10: 1-5: 1, and the yield is 50-60%;

the remaining steps (2) to (6) are the same as in example 1.

Example 3 Synthesis of threitol based polyurethane

On the basis of the product 6 obtained in example 1, the following procedure was carried out:

in N₂To a 50mL flask, 5mL of DMF and 0.268g (2.00mmol) of product 2 were added under ambient conditions and stirred well at room temperature; then 0.657g (2.00mmol) of the product 6 and 2% (w/w) of dibutyltin dilaurate catalyst were added and reacted at 120 ℃ for 48 hours; after completion of the reaction, the mixture was dropped into 50mL of methanol to precipitate, and the precipitate was filtered to give product 7(0.824 g) in 83.7% yield.