CN113956134B

CN113956134B - Method for efficiently preparing L-isopulegol from R-citronellal

Info

Publication number: CN113956134B
Application number: CN202111292871.1A
Authority: CN
Inventors: 王亚新; 董菁; 张永振
Original assignee: Wanhua Chemical Group Co Ltd
Current assignee: Wanhua Chemical Group Co Ltd
Priority date: 2021-11-03
Filing date: 2021-11-03
Publication date: 2022-09-20
Anticipated expiration: 2041-11-03
Also published as: CN113956134A

Abstract

The invention provides a method for efficiently preparing L-isopulegol from R-citronellal. The method is used for catalyzing R-citronellal to prepare L-isopulegol under the action of a catalyst prepared from (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol and trimethyl indium; in the preparation of the catalyst, the hydroxyl value and the water content in the inert solvent are controlled to be 100-500 mgKOH/kg; in the method for preparing the L-isopulegol, the hydroxyl value and the water content of the R-citronellal solution are controlled to be 100-500 mgKOH/kg. The preparation method of the invention can maintain high reaction rate and product selectivity, and high final conversion rate.

Description

Method for efficiently preparing L-isopulegol from R-citronellal

Technical Field

The invention relates to a method for efficiently preparing L-isopulegol from R-citronellal, belonging to the field of organic chemical synthesis.

Background

L-menthol, as a strong mint flavor perfume, is widely used in oral care products such as toothpaste and mouthwash, daily chemical products such as shampoo and shaving lotion, foods such as chewing gum and beverage, tobacco products, external drugs for clearing heat and relieving itching, internal drugs for clearing heat and benefiting throat, chiral inducers for synthesizing medical intermediates and the like due to the cooling effect, and is an important perfume product in the world.

L-isopulegol is an important intermediate for the artificial synthesis of L-menthol, the traditional method for obtaining L-isopulegol is the preparation using citronellal in a lewis acid catalyzed cyclization, and is usually obtained in the form of a mixture of four counterparts, i.e. isopulegol, iso-isopulegol, neo-isopulegol. But only L-menthol equivalent to natural molecules has commercial value due to the pure mint flavor and strong cooling effect. Therefore, the large-scale artificial synthesis of L-menthol has extremely high technical difficulty, and the artificial synthesis of L-menthol in China completely depends on import and is high in price. In conclusion, the development of the domestic efficient green technology for preparing the L-menthol with the independent intellectual property rights has important economic value and social significance.

Synthesis 1978,147 reports the preparation of isopulegol by cyclization of citronellal using zinc bromide. The reported yield is about 92%, while the enantioselectivity (ratio of isopulegol to the other isopulegol isomers) only reaches 94/6, which is too low compared to other processes. And the zinc bromide used in the process has serious corrosion resistance to equipment, and is not beneficial to controlling the cost in industrial production.

US 2002/0133046 a1 describes a process for the preparation of isopulegol by the cyclisation of citronellal using tris (aryloxy) aluminium as a catalyst. Although the enantioselectivity (the ratio of isopulegol to other isopulegol isomers) reaches 99.7/0.3 under the action of the catalyst, and the yield reaches 95.3% at most, according to a substance system of the catalyst used by the catalyst, the yield mentioned in the patent is difficult to achieve through practical verification, and meanwhile, the system has higher requirements on the water content and the hydroxyl value in raw materials and solvents, but the catalyst is not mentioned in the patent. This inevitably leads to a certain amount of loss of raw materials and solvents in the industrial process, which in turn leads to higher industrial cost.

In CN 101087746B patent, tris (aryloxy) aluminium is also used as a catalyst to catalyze the cyclization of citronellal to produce isopulegol, and in this process, the use of: I. at least one acid and/or II at least one compound selected from the group consisting of carboxylic anhydrides, aldehydes, ketones and vinyl ethers. The catalyst has higher feeding amount, larger operation burden can be brought in the expensive post-treatment process of the catalyst, and simultaneously, the separation of the auxiliary agent and the product is difficult, and the same cost problem also exists.

Therefore, a better method needs to be found, so that the high-efficiency utilization of the catalyst is realized, the influence of poisoning catalyst factors such as water content hydroxyl value and the like in the system is reduced, the cost of the catalyst is reduced, and the loss of raw materials and solvents is reduced to the extent that the industrial scale production can accept the catalyst.

Disclosure of Invention

The invention aims to provide a method for efficiently preparing isopulegol from citronellal, which has mild reaction conditions and high enantioselectivity and is suitable for industrial production and application.

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

a method for efficiently preparing L-isopulegol from R-citronellal, wherein the method is used for catalyzing the R-citronellal to prepare the L-isopulegol under the action of a catalyst prepared from (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol and trimethylindium; wherein, in the preparation process of the catalyst, the hydroxyl value and the water content in the inert solvent are controlled to be 100-500 mgKOH/kg; in the preparation process of the L-isopulegol, the hydroxyl value and the water content of the R-citronellal solution are controlled to be 100-500 mgKOH/kg; the water content of 1ppm is equivalent to 3.11 mgKOH/kg.

In the invention, the (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol ligand has a group with large steric hindrance, and a catalyst formed after coordination with trimethyl indium has a steric hindrance which can form proper steric hindrance around a phenolic hydroxyl group and can form a reaction transition state with proper steric hindrance with a reactant citronellal, so that the generation of impurities such as isopulegol isomer and isopulegone isomer is reduced, the citronellal is prevented from generating Tishchenko reaction, the intramolecular cyclization of citronellal is facilitated, and the reaction selectivity is improved.

Meanwhile, the tolerance of the catalyst generated by complexing and coordinating trimethyl indium and (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol ligand to water content and hydroxyl value is far higher than that of aluminum-based catalysts such as tris (aryloxy) aluminum and the like, so that the control of the water content in raw materials and solvents of the catalyst is reduced to an acceptable range, the loss is greatly reduced, and the cost is reduced. The catalyst can also realize the cyclization of R-citronellal with high enantioselectivity to prepare isopulegol; the ideal catalytic effect can be achieved under the mild condition close to room temperature, and higher reaction rate, product selectivity and conversion rate are kept.

In the invention, the preparation steps of the catalyst are as follows:

s1: adding (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol into a solvent, and uniformly stirring to prepare a solution A;

s2: and adding the trimethyl indium solution into the solution A, and uniformly stirring to finish the preparation of the catalyst.

In the invention, the (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol has the following structure:

preferably, the mass fraction of the (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol in the S1 solution A is 10-30%.

In the present invention, the solvent of S1 is an inert solvent, preferably one or more of xylene, toluene, benzene, n-hexane, cyclohexane, and dichloromethane, and more preferably toluene.

In the present invention, the S1 is performed in an inert gas atmosphere, and the inert gas is nitrogen and/or argon, preferably high purity nitrogen, more preferably high purity nitrogen having an oxygen content of less than 20ppm (v/v).

In the invention, in the preparation process of the catalyst of S1, the method for controlling the hydroxyl value and the water content in the inert solvent is batch rectification; preferably, the batch distillation uses a rectifying tower with more than or equal to 15 theoretical plates, the reflux ratio is controlled to be more than or equal to 3:1, and inert solvent and light components accounting for more than or equal to 5 wt% of the total feed mass are extracted.

In the invention, the molar ratio of the trimethylindium to the (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol in the S2 is 1 (1.5-2); preferably, the mass fraction of the S2 trimethyl indium solution is 25-35%; the solvent used is an inert solvent, preferably one or more of xylene, toluene, benzene, n-hexane, cyclohexane, dichloromethane, more preferably toluene.

In the invention, the trimethyl indium solution of S2 is slowly added dropwise.

In the invention, after the dropwise addition of the S2 is finished, the stirring is continued for more than 3 hours.

In the present invention, the S2 is performed in an inert gas atmosphere, and the inert gas is nitrogen and/or argon, preferably high purity nitrogen, more preferably high purity nitrogen having an oxygen content of less than 20ppm (v/v).

In the invention, the preparation method of the L-isopulegol comprises the following steps: adding a catalyst into a reactor, cooling to the reaction temperature, adding R-citronellal, and reacting to obtain an L-isopulegol product.

In the invention, in the preparation process of the L-isopulegol, the method for controlling the hydroxyl value and the water content of the R-citronellal solution is batch rectification; preferably, the batch distillation uses a rectifying tower with more than or equal to 30 theoretical plates, the reflux ratio is controlled to be more than or equal to 5:1, a toluene solvent with more than or equal to 5 wt% of the mass of the solution is added into citronellal, and light components with more than or equal to 7 wt% of the mass of the total feed are extracted.

In the invention, the molar ratio of indium to R-citronellal contained in the catalyst in the method is 1 (500-1000).

In the invention, the R-citronellal is dropwise added at a constant speed; preferably, the dropping time of the R-citronellal is 1-2 h.

In the invention, the reaction time is 4-6h, and the reaction temperature is 10-20 ℃.

Another object of the present invention is to provide an L-isopulegol.

L-isopulegol is prepared by the preparation method of the L-isopulegol.

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

(1) the preparation method of the L-isopulegol can keep higher reaction rate and product selectivity and more than 99 percent of final conversion rate.

(2) Meanwhile, the ratio of the raw materials to the catalyst is high, reaction conditions required by adding reaction auxiliaries are avoided, the subsequent operation process is greatly simplified, the operation frequency is reduced, and the method has industrial operation value.

Detailed Description

The following examples are provided to further illustrate the technical solutions provided by the present invention, but the present invention is not limited to the listed examples, and includes any other known modifications within the scope of the claims of the present invention.

Gas chromatograph: agilent 7890, chromatographic column INNO-WAX, inlet temperature: 300 ℃; the split ratio is 50: 1; carrier gas flow: 30 ml/min; temperature rising procedure: 80-230 ℃,3 ℃/min, FID detector temperature: 280 ℃.

The water content detection method comprises the following steps: refer to GB/T6283-;

the hydroxyl value detection method comprises the following steps: reference is made to method A, phthalic anhydride method, GB/T12008.3-2009;

toluene, not less than 99.5%, chemical reagents of national drug group limited;

(S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol, 98 wt%, Aladdin reagent Co., Ltd;

trimethylindium, 98 wt%, Aladdin reagent, Inc.;

r-citronellal, 98 wt%, national drug group chemical agents, Inc.;

nitrogen, 99%, bright torch gases ltd (oxygen content less than 20ppm (v/v)).

Example 1

600g of toluene solution (chemical purity > 99.5%) were distilled batchwise in a glass laboratory column with an internal diameter of 50mm, equipped with a ring-shaped triangular spiral packing of 0.5m 3mm x 3mm theta (theoretical plate number about 15) at a head pressure of 30 kPaA.

At a reflux ratio of 3:1, the bottom temperature was 96 ℃ and the top temperature was 45 ℃. About 30g of liquid distillate was withdrawn at about 5 ℃ in the overhead condenser. About 500g of toluene solution (chemical purity > 99.5%) was continuously withdrawn under these conditions, and the water content was determined to be 454mgKOH/kg, and the hydroxyl value content was 33 mgKOH/kg.

Example 2

At a reflux ratio of 5:1, the bottom temperature was 96 ℃ and the top temperature was 45 ℃. About 30g of liquid distillate was withdrawn at about 5 ℃ in the overhead condenser. About 500g of toluene solution (chemical purity > 99.5%) was continuously withdrawn under these conditions, and the water content was measured to be 201mgKOH/kg and the hydroxyl value content was 22 mgKOH/kg.

Example 3

About 600g of toluene solution (chemical purity > 99.5%) were distilled batchwise in a glass laboratory column with an internal diameter of 50mm, equipped with a ring-shaped triangular spiral packing of 0.7m 3mm x 3mm theta (theoretical plate number about 21) at a head pressure of 30 kPaA.

At a reflux ratio of 5:1, the bottom temperature was 110 ℃ and the top temperature was 45 ℃. About 42g of liquid distillate was withdrawn in the overhead condenser at about 5 ℃. About 500g of toluene solution (chemical purity > 99.5%) was continuously extracted under the conditions, and the water content was determined to be mgKOH/kg, and the hydroxyl value was not detected.

Example 4

A mixed solution of 570g citronellal and 30g toluene (chemical purity > 99.5%) was distilled batchwise in a glass laboratory column (theoretical plate number about 30) having an internal diameter of 50mm equipped with a 1m 3mm x 3mm theta ring triangular spiral packing under a top pressure gradually decreasing from 30kPaA to 1 kPaA.

The bottom temperature was 110 ℃ at a reflux ratio of 5: 1. About 42g of liquid distillate was withdrawn in the overhead condenser at about 5 ℃. Under the condition, about 500g of citronellal solution (chemical purity > 99.5%) is continuously extracted, the detected water content is 475mgKOH/kg, and the hydroxyl value content is 21 mgKOH/kg.

Example 5

A mixed solution of 570g citronellal and 40g toluene (chemical purity > 99.5%) was distilled batchwise in a glass laboratory column (theoretical plate number about 30) having an internal diameter of 50mm equipped with a 1m 3mm x 3mm theta ring triangular spiral packing under a top pressure gradually decreasing from 30kPaA to 1 kPaA.

The bottom temperature was 110 ℃ at a reflux ratio of 6: 1. About 52g of liquid distillate was withdrawn at about 5 ℃ in the overhead condenser. Under the condition, about 500g of citronellal solution (chemical purity > 99.5%) is continuously extracted, the detected water content is 301mgKOH/kg, and the hydroxyl value is not detected.

Example 6

The bottom temperature was 110 ℃ at a reflux ratio of 7: 1. About 48g of liquid distillate was withdrawn at about 5 ℃ in the overhead condenser. Under the condition, about 500g of citronellal solution (chemical purity > 99.5%) is continuously extracted, the detected water content is 102mgKOH/kg, and the hydroxyl value is not detected.

Example 7

In the examples, dehydrated toluene obtained by the method of example 1 and dehydrated citronellal obtained by the method of example 4 were selected.

Under the protection of high-purity nitrogen, 0.67g of (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol is added into 6.05g of toluene and stirred uniformly to prepare a solution A; slowly dripping 0.41g of 25 wt% trimethyl indium toluene solution into the solution A, and uniformly stirring; after the dropwise addition is finished for 0.5h, stirring is continued for 3h, and the preparation of the catalyst is finished.

Under the protection of high-purity nitrogen, 7.11g of the prepared catalyst solution is added into a jacketed reactor, the temperature is reduced to 10 ℃, and 100g R-citronellal is added into the jacketed reactor at a constant speed within 2 h. And continuing the reaction for 4 hours, and sampling to analyze the conversion rate and the selectivity of the citronellal in the solution.

The reaction results were as follows: the reaction selectivity was 98.12% and the reaction conversion was 98.55%.

The total content of hydroxyl value and water in citronellal in the toluene is 489mgKOH/kg, and the total content of hydroxyl value and water in citronellal is 496 mgKOH/kg.

Example 8

In the examples, dehydrated toluene obtained by the method of example 3 and dehydrated citronellal obtained by the method of example 6 were selected.

Under the protection of high-purity nitrogen, 0.67g of (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol is added into 2.69g of toluene and stirred uniformly to prepare a solution A; slowly dripping 0.35g of 30 wt% trimethyl indium toluene solution into the solution A, and uniformly stirring; after the dropwise addition is finished for 0.5h, stirring is continued for 4h, and the preparation of the catalyst is finished.

Under the protection of high-purity nitrogen, 3.68g of the prepared catalyst solution is added into a jacketed reactor, the temperature is reduced to 15 ℃, and 100g R-citronellal is added into the jacketed reactor at a constant speed within 1.5 h. And continuing the reaction for 5 hours, and sampling to analyze the conversion rate and the selectivity of the citronellal in the solution.

The reaction results were as follows: the reaction selectivity was 98.47% and the reaction conversion was 99.51%.

The total content of hydroxyl value and water in citronellal in the toluene is 103mgKOH/kg, and the total content of hydroxyl value and water in citronellal is 102 mgKOH/kg.

Example 9

In the examples, dehydrated toluene obtained by the method of example 2 and dehydrated citronellal obtained by the method of example 5 were selected.

Under the protection of high-purity nitrogen, 1.05g of (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol is added into 5.23g of toluene and stirred uniformly to prepare a solution A; slowly dripping 0.46g of 30 wt% trimethylindium toluene solution into the solution A, and uniformly stirring; after the dropwise addition is finished for 0.5h, stirring is continued for 3h, and the preparation of the catalyst is finished.

Under the protection of high-purity nitrogen, 5.65g of the prepared catalyst solution is added into a jacket reactor, the temperature is reduced to 15 ℃, and 100g R-citronellal is added into the jacket reactor at a constant speed within 1.5 h. And continuing the reaction for 5 hours, and sampling to analyze the conversion rate and the selectivity of the citronellal in the solution.

The reaction results were as follows: the reaction selectivity was 99.13% and the reaction conversion was 99.39%.

The total content of hydroxyl value and water in citronellal in the toluene used was 222mgKOH/kg, and the total content of hydroxyl value and water in citronellal was 301 mgKOH/kg.

Example 10

Under the protection of high-purity nitrogen, 1.79g of (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol is added into 16.13g of toluene and evenly stirred to prepare a solution A; slowly dripping 0.83g of 25 wt% trimethyl indium toluene solution into the solution A, and uniformly stirring; after the dropwise addition is finished for 0.5h, stirring is continued for 4h, and the preparation of the catalyst is finished.

Under the protection of high-purity nitrogen, 18.69g of the prepared catalyst solution is added into a jacketed reactor, the temperature is reduced to 10 ℃, and 100g R-citronellal is added into the jacketed reactor at a constant speed within 1 hour. And continuing the reaction for 4 hours, and sampling to analyze the conversion rate and the selectivity of the citronellal in the solution.

The reaction results were as follows: the reaction selectivity was 98.31% and the reaction conversion was 98.40%.

Example 11

Under the protection of high-purity nitrogen, 1.79g of (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol is added into 4.18g of toluene and stirred uniformly to prepare a solution A; slowly dripping 0.59g of toluene solution of 35 wt% of trimethyl indium into the solution A, and uniformly stirring; after the dropwise addition is finished for 0.5h, stirring is continued for 3h, and the preparation of the catalyst is finished.

Under the protection of high-purity nitrogen, 6.51g of the prepared catalyst solution is added into a jacketed reactor, the temperature is reduced to 20 ℃, and 100g R-citronellal is added into the jacketed reactor at a constant speed within 2 h. And continuing the reaction for 6h, and sampling to analyze the conversion rate and the selectivity of the citronellal in the solution.

The reaction results were as follows: the reaction selectivity was 99.79% and the reaction conversion was 99.98%.

Comparative example 1

The prior art solution of patent CN 101133067B, example 1, was adopted.

Cymboxal is cyclized to isopulegol in the presence of a catalyst prepared from ligand Ia1-1 and in the presence of acetic anhydride.

In a hot dry flask was added 1.05mmol of ligand Ia1-1 and 10ml of dry toluene. To the clear solution was added 350. mu.l (0.66mmol, 1 mol%) of a 25% strength solution of triethylaluminum in toluene at room temperature. The solution was stirred at 25 ℃ for 1 hour. After 5 minutes, a gel-like suspension of the catalyst was obtained. The catalyst suspension was cooled to 0 ℃ and a mixture of 10.15g (65.8mmol) of citronellal which had previously been cooled to 0 ℃ and 1% by weight of acetic anhydride (based on citronellal) was added over a period of 6 hours. The reaction mixture was stirred, samples were taken at regular intervals and hydrolyzed with 8% NaOH. In the process, the aluminum present precipitates out as hydroxide and a suspension is first obtained. After that, two clear phases were formed. The organic phase was analyzed by gas chromatography. The results are shown in the table below.

Citronellyl citronellate

The cyclization reaction produced isopulegol with a 90% selectivity based on all isopulegol isomers. The enantioselectivity (neo-isopulegol: neo-isopulegol: iso-isopulegol) was 0.4:99.4:0.2: 0.0.

Comparative example 2

In the examples, dehydrated toluene having a hydroxyl value and a total water content of 2095mgKOH/kg and dehydrated citronellal obtained by the method of example 6 were used.

Under the protection of high-purity nitrogen, 1.79g of (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol is added into 4.18g of toluene and stirred uniformly to prepare a solution A; slowly dripping 0.59g of toluene solution of 35 wt% of trimethyl indium into the solution A, and uniformly stirring; after the dropwise addition for 0.5h, stirring is continued for 3h, and the preparation of the catalyst is completed.

The reaction results were as follows: the reaction selectivity was 80.12% and the reaction conversion was 60.8%.

The total content of hydroxyl value and water in citronellal in the toluene is 2095mgKOH/kg, and the total content of hydroxyl value and water in citronellal is 102 mgKOH/kg.

Comparative example 3

In the examples, dehydrated toluene obtained by the method of example 3, dehydrated citronellal having a hydroxyl value and a total water content of 2095mgKOH/kg were selected.

The reaction results were as follows: the reaction selectivity was 90.55% and the reaction conversion was 72.84%.

The total content of hydroxyl value and water in citronellal in the toluene is 103mgKOH/kg, and the total content of hydroxyl value and water in citronellal is 2095 mgKOH/kg.

Comparative example 4

In the examples, dehydrated toluene having a total content of hydroxyl value and water of 2104mgKOH/kg and dehydrated citronellal having a total content of hydroxyl value and water of 2068mgKOH/kg were selected.

The reaction results were as follows: the reaction selectivity was 60.33% and the reaction conversion was 40.19%.

The total content of hydroxyl value and water in citronellal in the toluene used was 2104mgKOH/kg, and the total content of hydroxyl value and water in citronellal was 2068 mgKOH/kg.

It can be found by comparing the examples with the comparative examples that the reaction temperature is milder, the reaction rate is faster, the reaction conversion rate and the selectivity are higher, and the final ee value of the L- (-) -n-isopulegol is more advantageous.

It will be appreciated by those skilled in the art that modifications or adaptations to the invention may be made in light of the teachings of the present specification. Such modifications or adaptations are intended to be within the scope of the present invention as defined in the claims.

Claims

1. A method for efficiently preparing L-isopulegol from R-citronellal is characterized in that the method catalyzes R-citronellal to prepare the L-isopulegol under the action of a catalyst prepared from (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol and trimethylindium;

wherein, in the preparation process of the catalyst, the hydroxyl value and the water content in the inert solvent are controlled to be 100-500 mgKOH/kg; in the preparation process of the L-isopulegol, the hydroxyl value and the water content of the R-citronellal solution are controlled to be 100-500 mgKOH/kg; wherein the 1ppm water content is equivalent to 3.11 mgKOH/kg.

2. The method of producing L-isopulegol according to claim 1, characterized in that the catalyst production step is:

3. The process for producing L-isopulegol according to claim 2, characterized in that the (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol of S1 has the following structure:

and/or, the solvent of S1 is an inert solvent;

and/or the S1 is carried out in an inert gas atmosphere, wherein the inert gas is nitrogen and/or argon;

and/or, in the preparation process of the catalyst in S1, the method for controlling the hydroxyl value and the water content in the inert solvent is batch rectification.

4. The method for preparing L-isopulegol according to claim 3, characterized in that the mass fraction of (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol in the S1 solution A is 10-30%;

and/or the solvent of S1 is one or more of xylene, toluene, benzene, n-hexane, cyclohexane and dichloromethane;

and/or the inert gas of S1 is high-purity nitrogen;

the batch distillation uses a rectifying tower with more than or equal to 15 theoretical plates, the reflux ratio is controlled to be more than or equal to 3:1, and inert solvent and light components accounting for more than or equal to 5 wt% of the total feed mass are extracted.

5. The process for producing L-isopulegol according to claim 4, characterized in that the solvent of S1 is toluene;

and/or the inert gas of S1 is high-purity nitrogen with oxygen content less than 20v/v ppm.

6. The method for preparing L-isopulegol according to claim 2, characterized in that the molar ratio of trimethylindium to (S) -3,3 '-bis (2,4, 6-triisopropylphenyl) -1,1' -bi-2-naphthol in S2 is 1 (1.5-2);

and/or slowly dropwise adding the trimethyl indium solution of S2;

and/or after the dropwise addition of the S2 is finished, continuously stirring for not less than 3 hours;

and/or the S2 is carried out in an inert gas atmosphere, and the inert gas is nitrogen and/or argon.

7. The method for preparing L-isopulegol according to claim 6, characterized in that the mass fraction of the S2 trimethyl indium solution is 25-35%; the solvent is inert solvent;

and/or the inert gas of S2 is high-purity nitrogen.

8. The method for producing L-isopulegol according to claim 7, characterized in that the solvent of S2 is one or more of xylene, toluene, benzene, n-hexane, cyclohexane, dichloromethane;

and/or the inert gas of S2 is high-purity nitrogen with oxygen content less than 20v/v ppm.

9. The process for producing L-isopulegol according to claim 8, characterized in that the solvent of S2 is toluene.

10. The method of producing L-isopulegol according to claim 1, characterized in that the method of producing L-isopulegol is: adding a catalyst into a reactor, cooling to the reaction temperature, adding R-citronellal, and reacting to obtain an L-isopulegol product.

11. The method of producing L-isopulegol according to claim 10, wherein the method of controlling the hydroxyl value and water content of the R-citronellal solution during the production of L-isopulegol is batch distillation.

12. The process for producing L-isopulegol according to claim 11, characterized in that the batch distillation uses a distillation column having a theoretical plate number of not less than 30, the reflux ratio is controlled to be not less than 5:1, and light components are extracted in an amount of not less than 7 wt% based on the total feed mass.

13. The method for preparing L-isopulegol according to claim 10, characterized in that the molar ratio of indium contained in the catalyst to R-citronellal in the method is 1 (500-1000);

and/or, the R-citronellal is dropwise added at a constant speed;

and/or the reaction time is 4-6h, and the reaction temperature is 10-20 ℃.

14. The process of claim 13, wherein the R-citronellal is added dropwise over a period of 1 to 2 hours.