阅读说明：本技术 一种8-甲基葵醛的制备方法 (Preparation method of 8-methyl decanal ) 是由 谭亚菲 董鑫浩 郑华 雷国泰 朱小力 于 2021-09-07 设计创作，主要内容包括：本发明具体公开了一种8-甲基葵醛的制备方法,在本发明合成工艺中,从便宜易得的6-氯-1-己醇原料出发,首先在对甲苯磺酸催化下与二氢吡喃反应保护羟基,得到6-氯-己基四氢吡喃醚；之后6-氯-己基四氢吡喃醚与镁屑反应形成格式试剂,并在溴化亚铜催化下与1-溴-2-甲基-丁烷反应得到中间体8-甲基-葵基四氢吡喃醚；中间体不需提纯,直接在酸性条件下脱去羟基的保护,得到8-甲基-1-葵醇；最后使用2,2,6,6-四甲基哌啶氧化物氧化得到产物8-甲基葵醛；该合成工艺使用常见试剂,成本低,而且反应条件温和,收率高,适合大规模工业化生产,因此,在食品添加剂领域中有良好的应用前景。(The invention specifically discloses a preparation method of 8-methyl decanal, in the synthesis process of the invention, starting from cheap and easily available 6-chloro-1-hexanol raw material, firstly reacting with dihydropyran under the catalysis of p-toluenesulfonic acid to protect hydroxyl, and obtaining 6-chloro-hexyl tetrahydropyrane ether; then 6-chloro-hexyl tetrahydropyrane ether reacts with magnesium chips to form a Grignard reagent, and the Grignard reagent reacts with 1-bromo-2-methyl-butane under the catalysis of cuprous bromide to obtain an intermediate 8-methyl-decyl tetrahydropyrane ether; the intermediate does not need to be purified, and the protection of hydroxyl is directly removed under the acidic condition to obtain 8-methyl-1-decanol; finally, oxidizing by using 2,2,6, 6-tetramethylpiperidine oxide to obtain a product 8-methyl sunflower aldehyde; the synthesis process uses common reagents, has low cost, mild reaction conditions and high yield, and is suitable for large-scale industrial production, so the synthesis process has good application prospect in the field of food additives.)

1. The preparation method of 8-methyl pelargonic aldehyde is characterized by comprising the following steps:

hydroxyl protection of S1, 6-chloro-1-hexanol: mixing 6-chloro-1-hexanol and dihydropyran, adding a catalyst, and reacting to obtain 6-chloro-hexyl tetrahydropyrane ether;

preparation of S2, 8-methyl-decyl tetrahydropyrane ether: carrying out formatting reaction on the 6-chloro-hexyl tetrahydropyrane ether obtained in the step S1, and then reacting with 1-bromo-2-methyl-butane to obtain an intermediate crude product 8-methyl-decyl tetrahydropyrane ether;

s3, deprotection of 8-methyl-decyl tetrahydropyrane ether: removing protective groups of the intermediate crude product 8-methyl-decyl tetrahydropyrane ether obtained in the step S2 under an acidic condition to obtain 8-methyl-1-decanol;

s4 and preparation of 8-methyl pelargonic: and (4) carrying out oxidation reaction on the 8-methyl-1-decanol obtained in the step (S3) and an oxidant to obtain a product 8-methyl decanol.

2. The process for producing 8-methylpelargonic acid according to claim 1, wherein in step S1, the hydroxy group of 6-chloro-1-hexanol is protected as follows: adding p-toluenesulfonic acid and 6-chloro-1-hexanol into dichloromethane, introducing nitrogen for protection, maintaining the temperature of a reaction system at 0-10 ℃, slowly dropwise adding dihydropyran, continuously reacting for 1-2 hours after dropwise adding, then adding saturated sodium bicarbonate solution and water, separating out an organic phase, washing, drying, filtering, concentrating, and distilling to obtain 6-chloro-hexyl tetrahydropyrane ether.

3. The method for producing 8-methylpelargonic acid according to claim 2, wherein the molar ratio of the amounts of p-toluenesulfonic acid, 6-chloro-1-hexanol and dihydropyran used is (0.005-0.015): (1.2-1.8): (1-3).

4. The method for preparing 8-methylpelargonic acid according to claim 2, wherein the volume of dichloromethane is 4 to 6 times of the mass of 6-chloro-1-hexanol.

5. The method for preparing 8-methylpelargonic acid as claimed in claim 1, wherein in step S2, the specific synthesis method of 8-methyl-pelargonic tetrahydropyranyl ether is as follows: adding fine magnesium strips into tetrahydrofuran, introducing nitrogen for protection, adding iodine, slowly adding 1, 2-dibromoethane, slowly dropwise adding 6-chloro-hexyl tetrahydropyrane ether, controlling the reaction temperature to be not more than 60 ℃, continuously reacting for 2-3 hours after dropwise adding is finished, cooling the system temperature to 35-45 ℃, adding cuprous bromide, slowly dropwise adding 1-bromo-2-methyl-butane, continuously reacting for 5-8 hours after dropwise adding is finished, adding a saturated ammonium chloride solution and an organic solvent for extraction, separating an organic phase, washing, drying, filtering and concentrating to obtain a crude product of 8-methyl sunflower-based tetrahydropyrane ether.

6. The method for preparing 8-methyl-decanal according to claim 5, wherein the molar ratio of the magnesium strips, the 1, 2-dibromoethane, the 6-chloro-hexyl tetrahydropyrane ether, the cuprous bromide and the 1-bromo-2-methyl-butane is (15-20): (0.7-1.2): (8-12): (0.2-0.8): (8-12); the dosage of the iodine is 0.03-0.08 times of the mass of the 6-chloro-hexyl tetrahydropyrane ether; the volume dosage of the tetrahydrofuran is 4-6 times of the mass dosage of the 6-chloro-hexyl tetrahydropyrane ether; the volume dosage of the organic solvent is 8-12 times of the mass dosage of the 6-chloro-hexyl tetrahydropyrane ether.

7. The method for producing 8-methylpelargonic acid according to claim 1, wherein in step S3, the deprotection method of 8-methyl-pelargonic tetrahydropyranyl ether is as follows: adding crude 8-methyl sunflower-based tetrahydropyrane ether into methanol, slowly dropwise adding excessive acid solution, controlling the reaction temperature to be not more than 40 ℃, adjusting the pH of the system to be neutral, then adding brine, extracting with an organic solvent, separating out an organic phase, washing, drying, filtering, concentrating and distilling to obtain 8-methyl sunflower alcohol.

8. The preparation method of 8-methylpelargonic acid as claimed in claim 7, wherein the volume dosage of methanol is 4-6 times of the mass dosage of the crude 8-methylpelargonic tetrahydropyranyl ether; the volume usage of the organic solvent is 8-12 times of the mass usage of the crude 8-methyl sunflower-based tetrahydropyrane ether; the acidic solution is selected from one of hydrochloric acid, sulfuric acid, acetic acid and nitric acid.

9. The method for preparing 8-methyldecanal according to claim 1, wherein in step S4, the specific synthesis method of 8-methyldecanal is as follows: adding 2,2,6, 6-tetramethylpiperidine oxide, tetrabutylammonium hydrogen sulfate and sodium hypochlorite into a mixed solution of dichloromethane and water, reducing the temperature of a reaction system to 3-8 ℃, slowly dropwise adding 8-methyldecanol, continuing to react for 1-2 hours after dropwise adding, then adding a saturated sodium sulfite solution, separating an organic phase, extracting an aqueous phase with an organic solvent, combining the organic phases, washing, drying, filtering, concentrating and distilling to obtain the 8-methyldecanol.

10. The process for producing 8-methylpelargonic acid as claimed in claim 9, wherein the molar ratio of the amounts of 2,2,6, 6-tetramethylpiperidine oxide, tetrabutylammonium hydrogen sulfate, sodium hypochlorite and 8-methylpelargonic alcohol is (0.08 to 0.12): (0.02-0.08): (10-15): (8-12); the volume ratio of the dichloromethane to the water is (4-6): 1; the volume dosage of the dichloromethane is 4-6 times of the mass dosage of the 8-methyl decanol; the volume dosage of the organic solvent is 2-3 times of the mass dosage of the 8-methyl decanol.

Technical Field

The invention belongs to the technical field of chemical synthesis, and particularly relates to a preparation method of 8-methyl pelargonic.

Background

8-methyldecanol (CAS number: 127793-88-8) is naturally present in citrus fruits and 8-methyldecanol is approved by the US FDA and European Union for use in flavor (FEMA: 4795). 8-methyl sunflower aldehyde is widely used for preparing food additives such as citrus essence, fruit essence, candy essence and the like, and is an essence raw material with high commercial value.

Regarding the process for the preparation of 8-methyl-malvidin, the patent of Japan Kao corporation (EP0448740) discloses the following preparation process:

in the preparation process, 6-bromoethyl hexanoate is used as a raw material, and subjected to a Wittig reaction with 2-methylbutyraldehyde in the presence of triphenylphosphine and strong alkali sodium hydride to obtain 8-methyl-6-ethyl decenoate; then reducing with lithium aluminum hydride to obtain 8-methyl-6-decene-1-alcohol, then carrying out catalytic hydrogenation to obtain 8-methyl-1-decanol which is saturated alcohol, and finally oxidizing with pyridinium chlorochromate (PCC) to obtain the product 8-methyl decanol. Although the target product can be obtained in the preparation process, flammable and explosive metal organic reagents (sodium hydride and lithium aluminum hydride) are used in the preparation process route, and the reaction conditions require no water and no oxygen; in addition, the raw material 6-bromoethyl hexanoate is expensive, and byproducts of triphenyl phosphine oxide and chromium salt are not environment-friendly, so that the preparation process is not suitable for large-scale industrial production.

In addition, japanese patent No. JP2008100960 (gazette) discloses the following method for synthesizing 8-methyldecanol:

in the synthesis process, raw materials of 1-bromo-2-methylbutane and magnesium chips are reacted to form a Grignard reagent, then the Grignard reagent reacts with 6-bromo-hexanenitrile under the catalysis of cuprous bromide and in the presence of organic base N-methylpyrrolidone to obtain an intermediate 8-methyl-decanenitrile, and finally, diisobutylaluminum hydride (DIBAL) is used for reduction, and the product 8-methyl-decanal is obtained after acidic treatment. Although the reaction steps in the synthesis process are short, the raw material 1-bromo-2-methylbutane is expensive, the preparation of 6-bromo-hexanenitrile needs to use a highly toxic cyanide, and the diisobutylaluminum hydride reduction reaction is required to be carried out at a low temperature of-60 ℃, which is obviously not suitable for large-scale industrial production.

At present, the popularization and application of 8-methyl sunflower aldehyde are restricted by production, so that a new environment-friendly and cost-friendly process for preparing and synthesizing 8-methyl sunflower aldehyde is urgently needed.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a preparation method of 8-methyl sunflower aldehyde, which solves the problems that in the existing process for preparing 8-methyl sunflower aldehyde, the used raw materials are expensive, the generated by-products are not environment-friendly, and meanwhile, the preparation process is not suitable for large-scale industrial production.

In order to solve the problems in the prior art, the invention is realized by the following technical scheme:

a preparation method of 8-methyl pelargonic aldehyde comprises the following steps:

hydroxyl protection of S1, 6-chloro-1-hexanol: mixing 6-chloro-1-hexanol and dihydropyran, adding a catalyst, and reacting to obtain 6-chloro-hexyl tetrahydropyrane ether;

preparation of S2, 8-methyl-decyl tetrahydropyrane ether: carrying out formatting reaction on the 6-chloro-hexyl tetrahydropyrane ether obtained in the step S1, and then reacting with 1-bromo-2-methyl-butane to obtain an intermediate crude product 8-methyl-decyl tetrahydropyrane ether;

s3, deprotection of 8-methyl-decyl tetrahydropyrane ether: removing protective groups of the intermediate crude product 8-methyl-decyl tetrahydropyrane ether obtained in the step S2 under an acidic condition to obtain 8-methyl-1-decanol;

s4 and preparation of 8-methyl pelargonic: and (4) carrying out oxidation reaction on the 8-methyl-1-decanol obtained in the step (S3) and an oxidant to obtain a product 8-methyl decanol.

Further, in step S1, the hydroxyl group protection method of 6-chloro-1-hexanol is as follows: adding p-toluenesulfonic acid and 6-chloro-1-hexanol into dichloromethane, introducing nitrogen for protection, maintaining the temperature of a reaction system at 0-10 ℃, slowly dropwise adding dihydropyran, continuously reacting for 1-2 hours after dropwise adding, then adding saturated sodium bicarbonate solution and water, separating out an organic phase, washing, drying, filtering, concentrating, and distilling to obtain 6-chloro-hexyl tetrahydropyrane ether.

Further, the molar ratio of the p-toluenesulfonic acid, the 6-chloro-1-hexanol and the dihydropyran is (0.005-0.015): (1.2-1.8): (1-3).

Furthermore, the volume usage of the dichloromethane is 4-6 times of the mass usage of the 6-chloro-1-hexanol.

Further, in step S2, the specific synthesis method of 8-methyl-decyl tetrahydropyrane ether is as follows: adding fine magnesium strips into tetrahydrofuran, introducing nitrogen for protection, adding iodine, slowly adding 1, 2-dibromoethane, slowly dropwise adding 6-chloro-hexyl tetrahydropyrane ether, controlling the reaction temperature to be not more than 60 ℃, continuously reacting for 2-3 hours after dropwise adding is finished, cooling the system temperature to 35-45 ℃, adding cuprous bromide, slowly dropwise adding 1-bromo-2-methyl-butane, continuously reacting for 5-8 hours after dropwise adding is finished, adding a saturated ammonium chloride solution and an organic solvent for extraction, separating an organic phase, washing, drying, filtering and concentrating to obtain a crude product of 8-methyl sunflower-based tetrahydropyrane ether.

Further, the molar ratio of the magnesium strips, the 1, 2-dibromoethane, the 6-chloro-hexyl tetrahydropyrane ether, the cuprous bromide and the 1-bromo-2-methyl-butane is (15-20): (0.7-1.2): (8-12): (0.2-0.8): (8-12); the dosage of the iodine is 0.03-0.08 times of the mass of the 6-chloro-hexyl tetrahydropyrane ether; the volume dosage of the tetrahydrofuran is 4-6 times of the mass dosage of the 6-chloro-hexyl tetrahydropyrane ether; the volume dosage of the organic solvent is 8-12 times of the mass dosage of the 6-chloro-hexyl tetrahydropyrane ether.

Further, in step S3, the deprotection method of 8-methyl-decyl tetrahydropyrane ether is as follows: adding crude 8-methyl sunflower-based tetrahydropyrane ether into methanol, slowly dropwise adding excessive acid solution, controlling the reaction temperature to be not more than 40 ℃, adjusting the pH of the system to be neutral, then adding brine, extracting with an organic solvent, separating out an organic phase, washing, drying, filtering, concentrating and distilling to obtain 8-methyl sunflower alcohol.

Furthermore, the volume dosage of the methanol is 4-6 times of the mass dosage of the crude 8-methyl decyl tetrahydropyrane ether; the volume usage of the organic solvent is 8-12 times of the mass usage of the crude 8-methyl sunflower-based tetrahydropyrane ether; the acidic solution is selected from one of hydrochloric acid, sulfuric acid, acetic acid and nitric acid.

Further, in step S4, the specific synthesis method of 8-methyldecanol is as follows: adding 2,2,6, 6-tetramethylpiperidine oxide, tetrabutylammonium hydrogen sulfate and sodium hypochlorite into a mixed solution of dichloromethane and water, reducing the temperature of a reaction system to 3-8 ℃, slowly dropwise adding 8-methyldecanol, continuing to react for 1-2 hours after dropwise adding, then adding a saturated sodium sulfite solution, separating an organic phase, extracting an aqueous phase with an organic solvent, combining the organic phases, washing, drying, filtering, concentrating and distilling to obtain the 8-methyldecanol.

Further, the molar ratio of the 2,2,6, 6-tetramethylpiperidine oxide, the tetrabutylammonium hydrogen sulfate, the sodium hypochlorite and the 8-methyldecanol is (0.08-0.12): (0.02-0.08): (10-15): (8-12); the volume ratio of the dichloromethane to the water is (4-6): 1; the volume dosage of the dichloromethane is 4-6 times of the mass dosage of the 8-methyl decanol; the volume dosage of the organic solvent is 2-3 times of the mass dosage of the 8-methyl decanol.

The invention takes 6-chlorine-1-hexanol as a synthetic raw material, and finally 8-methyl sunflower aldehyde is prepared by hydroxyl protection of 6-chlorine-1-hexanol, preparation of 8-methyl-sunflower tetrahydropyran ether and deprotection of 8-methyl-sunflower tetrahydropyran ether, wherein the synthetic route is as follows:

the synthesis reaction is a new synthesis process, the raw materials are easy to obtain in the whole synthesis process, and the finally obtained product has high yield and is suitable for large-scale industrial production.

Compared with the prior art, the invention has the following advantages:

in the synthesis process, cheap and easily-obtained 6-chloro-1-hexanol raw material is used, and the raw material is reacted with dihydropyran under the catalysis of p-toluenesulfonic acid to protect hydroxyl to obtain 6-chloro-hexyl tetrahydropyrane ether; then 6-chloro-hexyl tetrahydropyrane ether reacts with magnesium chips to form a Grignard reagent, and the Grignard reagent reacts with 1-bromo-2-methyl-butane under the catalysis of cuprous bromide to obtain an intermediate 8-methyl-decyl tetrahydropyrane ether; the intermediate does not need to be purified, and the protection of hydroxyl is directly removed under the acidic condition to obtain 8-methyl-1-decanol; finally, oxidizing by using 2,2,6, 6-tetramethylpiperidine oxide to obtain a product 8-methyl sunflower aldehyde; the synthesis process uses common reagents, has low cost, mild reaction conditions and high yield, and is suitable for large-scale industrial production, so the synthesis process has good application prospect in the field of food additives.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a flow chart of the preparation process of 8-methyl pelargonic aldehyde.

Detailed Description

The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.

The raw materials and equipment used in the present invention are commercially available unless otherwise specified.

The invention provides a preparation method of 8-methyl pelargonic aldehyde, which comprises the following steps:

hydroxyl protection of S1, 6-chloro-1-hexanol: under the condition of catalysis of p-toluenesulfonic acid, 6-chloro-1-hexanol reacts with dihydropyran to obtain 6-chloro-hexyl tetrahydropyrane ether, and the specific reaction is as follows:

preparation of S2, 8-methyl-decyl tetrahydropyrane ether: reacting the 6-chloro-hexyl tetrahydropyrane ether obtained in the step S1 with magnesium chips to form a Grignard reagent, and reacting the Grignard reagent with 1-bromo-2-methyl-butane under the catalysis of cuprous bromide to obtain an intermediate crude product 8-methyl-decyl tetrahydropyrane ether, wherein the reaction is as follows:

s3, deprotection of 8-methyl-decyl tetrahydropyrane ether: under an acidic condition, removing a protecting group from the intermediate crude product 8-methyl-decyl tetrahydropyrane ether obtained in the step S2 to obtain 8-methyl-1-decanol, wherein the specific reaction is as follows:

s4 and preparation of 8-methyl pelargonic: carrying out oxidation reaction on the 8-methyl-1-decanol obtained in the step S3 and an oxidant to obtain a product 8-methyl decanol, wherein the specific reaction is as follows:

example 1

A preparation method of 8-methyl pelargonic aldehyde comprises the following steps:

hydroxyl protection of S1, 6-chloro-1-hexanol: adding 80ml of dichloromethane into a three-necked flask with a stirring, dropping funnel and a thermometer, and starting stirring; adding 0.086g of p-toluenesulfonic acid and 16.44g of 6-chloro-1-hexanol, introducing nitrogen for protection, maintaining the temperature of the reaction system at 0-10 ℃, and slowly adding 8.4g of 3, 4-dihydropyran through a dropping funnel; due to the reaction heat release, the dropping speed is controlled, so that the temperature of a reaction system is maintained at 0-10 ℃; after the dropwise addition is finished, continuously reacting for 1-2 h under a low-temperature condition; then adding 40ml of saturated sodium bicarbonate solution, stirring for 10-15 min, adding 20ml of water, transferring to a separating funnel to separate an organic phase, washing with 50ml of saturated sodium chloride solution, adding a proper amount of anhydrous sodium sulfate, drying, filtering and concentrating to obtain 24.56g of crude product;

after short-path vacuum distillation, 24.33g of the product 6-chloro-hexyl tetrahydropyrane ether is obtained, the temperature is 145 ℃/0.16mmHg, and the yield is 91.8% (the molecular weight of the product is 220.74, and the theoretical yield is 26.5 g);

preparation of S2, 8-methyl-decyl tetrahydropyrane ether: 80ml of anhydrous tetrahydrofuran was added to a three-necked flask equipped with a stirring, dropping funnel and thermometer, and stirring was started; adding 3.6g of finely-divided magnesium strips, introducing nitrogen for protection, adding 0.6g of iodine, and slowly adding 1.316g of 1, 2-dibromoethane through a dropping funnel; because the reaction is exothermic, the reaction temperature is controlled not to exceed 60 ℃, 17.66g of 6-chloro-1-hexanol tetrahydropyrane ether is continuously and slowly added through a dropping funnel, because the reaction is exothermic, the dropping speed is noticed to control the reaction temperature not to exceed 60 ℃, after the dropping is finished, the heating is slowly carried out, the reaction system is kept refluxing slightly, after the reaction is carried out for 2-3 hours, the color of the solution is changed from yellow to be clear and then to be black, most magnesium strips disappear, at the moment, the heating is stopped, 0.286g of cuprous bromide is added after the temperature of the system is cooled to 35-45 ℃, then 7.55g of 1-bromo-2-methyl-butane is slowly dropped, after the dropping is finished, the heating is slowly carried out, the reaction system is kept refluxing slightly, the reaction is continuously carried out for 5-8 hours, 200ml of saturated ammonium chloride solution is added into the reaction mixture, and 200ml of ethyl acetate is added, then transferring to a separating funnel, separating an organic phase, washing with brine, adding a proper amount of anhydrous sodium sulfate, drying, filtering and concentrating to obtain 18.6g of a crude product of 8-methylsunflower tetrahydropyrane ether;

the crude product is directly used for next hydroxyl deprotection reaction without purification (the molecular weight of the product is 256.4, and the theoretical yield is 20.5 g);

s3, deprotection of 8-methyl-decyl tetrahydropyrane ether: adding 80ml of methanol into a three-neck flask with a stirring, dropping funnel and a thermometer, and starting stirring; adding 18.6g of crude 8-methyl sunflower-based tetrahydropyrane ether, slowly adding 40ml of 2M hydrochloric acid solution through a dropping funnel, paying attention to the dropping speed to control the reaction temperature not to exceed 40 ℃ due to reaction heat release, stirring at room temperature for 1-2 h after the dropping is finished, then adding sodium carbonate powder into a reaction mixture, adjusting the pH value to be neutral, then adding 100ml of brine, extracting twice with ethyl acetate, using 80ml each time, combining organic phases, washing the brine, adding a proper amount of anhydrous sodium sulfate, drying, filtering and concentrating to obtain 12.3g of crude;

after vacuum distillation and purification, 9.01g of the product 8-methyl decanol is obtained, 112 ℃/0.15mmHg, and the total yield of the two-step reaction is 65.4% (the product has the molecular weight of 172.3, and the theoretical yield is 13.8 g);

s4 and preparation of 8-methyl pelargonic: adding a mixed solution of 80ml of dichloromethane and 20ml of water into a three-necked flask with a stirring, dropping funnel and a thermometer, and starting stirring; adding 0.125g of 2,2,6, 6-tetramethylpiperidine oxide, 0.068g of tetrabutylammonium hydrogen sulfate and 7.4g of sodium hypochlorite, reducing the temperature to 3-8 ℃, slowly adding 13.784g of 8-methyldecanol through a dropping funnel, continuously reacting for 1-2 hours at 3-8 ℃ after the addition is finished, adding 50ml of saturated sodium sulfite solution into the reaction mixture, separating an organic phase, extracting an aqueous phase once by using 40ml of dichloromethane, combining the organic phases, washing the brine, adding a proper amount of anhydrous sodium sulfate, drying, filtering and concentrating to obtain 13.4g of a crude product;

after vacuum distillation and purification, 12.7g of the product 8-methyl sunflower aldehyde is obtained, 108 ℃/0.15mmHg, and the yield is 93.2% (the product molecular weight is 170.3, and the theoretical yield is 13.6 g).

Example 2

A preparation method of 8-methyl pelargonic aldehyde comprises the following steps:

hydroxyl protection of S1, 6-chloro-1-hexanol: adding 100ml of dichloromethane into a three-necked flask with a stirring, dropping funnel and a thermometer, and starting stirring; adding 0.2g of p-toluenesulfonic acid and 20g of 6-chloro-1-hexanol, introducing nitrogen for protection, maintaining the temperature of the reaction system at 0-10 ℃, and slowly adding 16.8g of 3, 4-dihydropyran through a dropping funnel; due to the reaction heat release, the dropping speed is controlled, so that the temperature of a reaction system is maintained at 0-10 ℃; after the dropwise addition is finished, continuously reacting for 1-2 h under a low-temperature condition; then adding 40ml of saturated sodium bicarbonate solution, stirring for 10-15 min, adding 20ml of water, transferring to a separating funnel to separate an organic phase, washing with 50ml of saturated sodium chloride solution, adding a proper amount of anhydrous sodium sulfate, drying, filtering and concentrating to obtain 35.06g of crude product;

29.42g of 6-chloro-hexyl tetrahydropyrane ether is obtained after short-range vacuum distillation, the temperature is 145 ℃/0.16mmHg, and the yield is 92.1% (the molecular weight of the product is 220.74, and the theoretical yield is 32 g);

preparation of S2, 8-methyl-decyl tetrahydropyrane ether: adding 100ml of anhydrous tetrahydrofuran into a three-neck flask with a stirring funnel, a dropping funnel and a thermometer, and starting stirring; adding 4.4g of finely-divided magnesium strips, introducing nitrogen for protection, adding 1.0g of iodine, and slowly adding 1.6g of 1, 2-dibromoethane through a dropping funnel; because the reaction releases heat, the reaction temperature is controlled not to exceed 60 ℃, 22.0g of 6-chloro-1-hexanol tetrahydropyrane ether is continuously and slowly added through a dropping funnel, because the reaction releases heat, the dropping speed is noticed to control the reaction temperature not to exceed 60 ℃, after the dropping is finished, the heating is slowly carried out, the reaction system is kept refluxing slightly, after the reaction is carried out for 2 to 3 hours, the color of the solution is changed from yellow to clear and then to black, most magnesium strips disappear, at the moment, the heating is stopped, 0.72g of cuprous bromide is added after the temperature of the system is cooled to 35 to 45 ℃, then 15.1g of 1-bromo-2-methyl-butane is slowly dropped, after the dropping is finished, the heating is slowly carried out, the reaction system is kept refluxing slightly, the reaction is continuously carried out for 5 to 8 hours, 200ml of saturated ammonium chloride solution is added into the reaction mixture, and 200ml of ethyl acetate is added, then transferring to a separating funnel, separating an organic phase, washing with brine, adding a proper amount of anhydrous sodium sulfate, drying, filtering and concentrating to obtain 23.1g of a crude product of 8-methylsunflower tetrahydropyrane ether;

the crude product is directly used for next hydroxyl deprotection reaction without purification (the molecular weight of the product is 256.4, and the theoretical yield is 25.6 g);

s3, deprotection of 8-methyl-decyl tetrahydropyrane ether: adding 100ml of methanol into a three-neck flask with a stirring, dropping funnel and a thermometer, and starting stirring; adding 23.1g of crude 8-methyl sunflower-based tetrahydropyrane ether, slowly adding 40ml of 2M hydrochloric acid solution through a dropping funnel, paying attention to the dropping speed to control the reaction temperature not to exceed 40 ℃ due to reaction heat release, stirring at room temperature for 1-2 h after the dropping is finished, then adding sodium carbonate powder into a reaction mixture, adjusting the pH value to be neutral, then adding 100ml of brine, extracting twice with ethyl acetate, using 100ml each time, combining organic phases, washing the brine, adding a proper amount of anhydrous sodium sulfate, drying, filtering and concentrating to obtain 15.1g of crude;

after vacuum distillation and purification, 11.4g of the product 8-methyl decanol is obtained, the temperature is 112 ℃/0.15mmHg, and the total yield of the two-step reaction is 66.3% (the product has the molecular weight of 172.3, and the theoretical yield is 17.2 g);

s4 and preparation of 8-methyl pelargonic: adding a mixed solution of 100ml of dichloromethane and 20ml of water into a three-neck flask provided with a stirring, dropping funnel and a thermometer, and starting stirring; adding 0.19g of 2,2,6, 6-tetramethylpiperidine oxide, 0.17g of tetrabutylammonium hydrogen sulfate and 8.9g of sodium hypochlorite, reducing the temperature to 3-8 ℃, slowly adding 17.03g of 8-methyldecanol through a dropping funnel, continuously reacting for 1-2 hours at the temperature of 3-8 ℃ after the dropwise addition is finished, adding 50ml of saturated sodium sulfite solution into the reaction mixture, separating an organic phase, extracting an aqueous phase once with 50ml of dichloromethane, combining the organic phases, washing with brine, adding a proper amount of anhydrous sodium sulfate, drying, filtering and concentrating to obtain 16.8g of a crude product;

after vacuum distillation and purification, 16.2g of the product 8-methyl sunflower aldehyde is obtained, 108 ℃/0.15mmHg, and the yield is 95.3% (the product molecular weight is 170.3, and the theoretical yield is 17.0 g).

Example 3

A preparation method of 8-methyl pelargonic aldehyde comprises the following steps:

hydroxyl protection of S1, 6-chloro-1-hexanol: adding 120ml of dichloromethane into a three-necked flask provided with a stirring, dropping funnel and a thermometer, and starting stirring; adding 0.258g of p-toluenesulfonic acid and 24.66g of 6-chloro-1-hexanol, introducing nitrogen for protection, maintaining the temperature of the reaction system at 0-10 ℃, and slowly adding 25.2g of 3, 4-dihydropyran through a dropping funnel; due to the reaction heat release, the dropping speed is controlled, so that the temperature of a reaction system is maintained at 0-10 ℃; after the dropwise addition is finished, continuously reacting for 1-2 h under a low-temperature condition; then adding 60ml of saturated sodium bicarbonate solution, stirring for 10-15 min, adding 40ml of water, transferring to a separating funnel to separate an organic phase, washing with 80ml of saturated sodium chloride solution, adding a proper amount of anhydrous sodium sulfate, drying, filtering and concentrating to obtain 42.5g of crude product;

after short-path vacuum distillation, 36.5g of the product 6-chloro-hexyl tetrahydropyrane ether is obtained, the temperature is 145 ℃/0.16mmHg, and the yield is 91.9 percent (the molecular weight of the product is 220.74, and the theoretical yield is 39.7 g);

preparation of S2, 8-methyl-decyl tetrahydropyrane ether: adding 120ml of anhydrous tetrahydrofuran into a three-neck flask with a stirring funnel, a dropping funnel and a thermometer, and starting stirring; adding 4.8g of finely-divided magnesium strips, introducing nitrogen for protection, adding 1.6g of iodine, and slowly adding 2.256g of 1, 2-dibromoethane through a dropping funnel; because the reaction releases heat, the reaction temperature is controlled not to exceed 60 ℃, 26.5g of 6-chloro-1-hexanol tetrahydropyrane ether is continuously and slowly added through a dropping funnel, because the reaction releases heat, the dropping speed is noticed to control the reaction temperature not to exceed 60 ℃, after the dropping is finished, the heating is slowly carried out, the reaction system is kept refluxing slightly, after the reaction is carried out for 2 to 3 hours, the color of the solution is changed from yellow to clear and then to black, most magnesium strips disappear, at the moment, the heating is stopped, 1.144g of cuprous bromide is added after the temperature of the system is cooled to 35 to 45 ℃, then 18.12g of 1-bromo-2-methyl-butane is slowly dropped, after the dropping is finished, the heating is slowly carried out, the reaction system is kept refluxing slightly, the reaction is continuously carried out for 5 to 8 hours, 250ml of saturated ammonium chloride solution is added into the reaction mixture, and 300ml of ethyl acetate is added, then transferring to a separating funnel, separating an organic phase, washing with brine, adding a proper amount of anhydrous sodium sulfate, drying, filtering and concentrating to obtain 28.5g of a crude product of 8-methylsunflower tetrahydropyrane ether;

the crude product is directly used for next hydroxyl deprotection reaction without purification (the molecular weight of the product is 256.4, and the theoretical yield is 30.8 g);

s3, deprotection of 8-methyl-decyl tetrahydropyrane ether: adding 120ml of methanol into a three-neck flask with a stirring, dropping funnel and a thermometer, and starting stirring; adding 28.5g of crude 8-methyl decyl tetrahydropyrane ether, slowly adding 60ml of 2M hydrochloric acid solution through a dropping funnel, paying attention to the dropping speed to control the reaction temperature not to exceed 40 ℃ due to reaction heat release, stirring at room temperature for 1-2 h after dropping is finished, then adding sodium carbonate powder into a reaction mixture, adjusting the pH value to be neutral, then adding 150ml of brine, extracting twice with ethyl acetate, using 150ml each time, combining organic phases, washing the brine, adding a proper amount of anhydrous sodium sulfate, drying, filtering and concentrating to obtain 18.5g of crude product;

after vacuum distillation and purification, 13.3g of the product 8-methyl decanol is obtained, the temperature is 112 ℃/0.15mmHg, and the total yield of the two steps of reaction is 64.8% (the product has the molecular weight of 172.3, and the theoretical yield is 20.7 g);

s4 and preparation of 8-methyl pelargonic: adding a mixed solution of 120ml of dichloromethane and 20ml of water into a three-neck flask provided with a stirring, dropping funnel and a thermometer, and starting stirring; adding 0.192g of 2,2,6, 6-tetramethylpiperidine oxide, 0.27g of tetrabutylammonium hydrogen sulfate and 11.16g of sodium hypochlorite, reducing the temperature to 3-8 ℃, slowly adding 20.4g of 8-methyldecanol through a dropping funnel, continuously reacting for 1-2 hours at the temperature of 3-8 ℃ after the dropwise addition is finished, adding 80ml of saturated sodium sulfite solution into the reaction mixture, separating an organic phase, extracting an aqueous phase once with 80ml of dichloromethane, combining the organic phases, washing with brine, adding a proper amount of anhydrous sodium sulfate, drying, filtering and concentrating to obtain 19.5g of a crude product;

after vacuum distillation and purification, 19.09g of the product 8-methyl sunflower aldehyde is obtained, 108 ℃/0.15mmHg, and the yield is 93.6% (the product molecular weight is 170.3, and the theoretical yield is 20.4 g).

Comparative example 1

The synthesis was carried out according to the 8-methyldecanol synthesis method disclosed in the Japanese Changchuan company patent (JP 2008100960).

The yield of the prepared 8-methyl sunflower aldehyde is 88 percent.

The yield of the 8-methyl sunflower aldehyde prepared in the embodiments 1-3 of the invention is about 95%, which is higher than that of the conventional 8-methyl sunflower aldehyde synthesized conventionally, and in addition, the synthesis process uses common reagents, has low cost, mild reaction conditions and high yield, and is suitable for large-scale industrial production, so the synthesis process has a good application prospect in the field of food additives.

Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being included therein.