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Method for asymmetric synthesis of levorotation menthol

A kind of L-menthol, asymmetric technology, applied in the field of three-step reaction synthesis of L-menthol, can solve the problems of trans-citral difficult to reuse, high production equipment requirements, etc., to achieve simple catalyst preparation, mild reaction conditions, and synthetic process simple effect

Inactive Publication Date: 2013-04-17
GUANGDONG FOOD IND INST +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0012] The synthesis process of this synthetic route is simple, but the rectification of the cis-trans isomer mixture of citral to obtain the cis configuration requires high production equipment, and the obtained trans-citral is difficult to reuse

Method used

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  • Method for asymmetric synthesis of levorotation menthol
  • Method for asymmetric synthesis of levorotation menthol
  • Method for asymmetric synthesis of levorotation menthol

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0036] 1. Catalytic asymmetric hydrogenation

[0037] Take a 250ml three-necked flask, add citral (15.2g, 0.1mol), (R)-2-[bis(4-ethylphenyl)]methyltetrahydropyrrole (29.3mg , 0.1mmol), trifluoroacetic acid (12mg, 0.1mmol), 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate diethyl ester (75.9g, 0.3mol), and Add 80 mL of tetrahydrofuran to dissolve the solid. Stir at room temperature for 10 h, remove the solvent under reduced pressure, and purify by column chromatography to obtain 12.9 g of (R)-citronellal light yellow liquid with a yield of 84%.

[0038] 2. Ring closing reaction

[0039] 5°C, N 2 ZnBr 2 (1.35g, 6mmol) was added in portions to a stirred solution of (R)-citronellal (4.6g, 30mmol) in toluene (30mL), and the resulting reaction compound was stirred at 5-10°C for 0.5h. Filter, rinse ZnBr with n-hexane (10mL) 2 . The filtrate was successively washed with H 2 O (30mL), saturated NaHCO 3 solution (30mL) and saturated brine (30mL) for washing. anhydrous MgSO ...

Embodiment 2

[0043] 1. Catalytic asymmetric hydrogenation

[0044] Take a 250ml three-necked flask, add citral (15.2g, 0.1mol), (R)-2-[bis(4-ethylphenyl)]methyltetrahydropyrrole (29.3mg , 0.1mmol), trifluoroacetic acid (12mg, 0.1mmol), 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate diethyl ester (75.9g, 0.3mol), and Add 80ml of tetrahydrofuran to dissolve the solid, stir at -20°C for 20h, remove the solvent under reduced pressure, and purify by column chromatography to obtain 8.7g of (R)-citronellal light yellow liquid with a yield of 71%.

[0045] 2. Ring closing reaction

[0046] 5°C, N 2 ZnBr 2 (1.35g, 6mmol) was added in portions to a stirred solution of (R)-citronellal (4.6g, 30mmol) in toluene (30mL), and the resulting reaction compound was stirred at 5-10°C for 0.5h. Filter, rinse ZnBr with n-hexane (10mL) 2 . The filtrate was successively washed with H 2 O (30mL), saturated NaHCO 3 solution (30mL) and saturated brine (30mL) for washing. anhydrous MgSO 4 After drying, th...

Embodiment 3

[0050] 1. Catalytic asymmetric hydrogenation

[0051] Take a 250ml three-necked flask, add citral (15.2g, 0.1mol), (R)-2-[bis(4-ethylphenyl)]methyltetrahydropyrrole (29.3mg , 0.1mmol), trifluoroacetic acid (12mg, 0.1mmol), 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate diethyl ester (75.9g, 0.3mol), and Add 80 mL of tetrahydrofuran to dissolve the solid. Stir at 40°C for 10 h, remove the solvent under reduced pressure, and purify by column chromatography to obtain 10.3 g of (R)-citronellal light yellow liquid with a yield of 74%.

[0052] 2. Ring closing reaction

[0053] 5°C, N 2 ZnBr 2 (1.35g, 6mmol) was added in portions to a stirred solution of (R)-citronellal (4.6g, 30mmol) in toluene (30mL), and the resulting reaction compound was stirred at 5-10°C for 0.5h. Filter, rinse ZnBr with n-hexane (10mL) 2 . The filtrate was successively washed with H 2 O (30mL), saturated NaHCO 3 solution (30mL) and saturated brine (30mL) for washing. anhydrous MgSO 4 After dryi...

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Abstract

The invention discloses a method for asymmetric synthesis of levorotation menthol. The method comprises the following steps: citral is taken as an initial raw material, a dihydropyridine derivant is taken as a negative hydrogen source, chiral amine serves as a chiral auxiliary agent for catalytic and asymmetric hydrogenization synthesis of dextrorotation citronellal, the dextrorotation citronellal is catalyzed by Lewis acid for ring-closing synthesis of levorotation isopulegol, and the levorotation isopulegol is subject to catalytic hydrogenation to finally produce the levorotation menthol. The total yield of the levorotation menthol produced by adopting the method is larger than 60 percent, and the ee (enantiomeric excess) value is larger than 90 percent. The method has the characteristics of mild reaction conditions, simple synthetic process, simplicity in catalyst preparation, convenience in catalyst recovery and the like and is suitable for large-scale industrial production of levorotation menthol.

Description

technical field [0001] The invention belongs to the technical field of asymmetric synthesis of organic chemistry, and in particular relates to a method for synthesizing L-menthol by using citral as a starting material through three-step reactions. Background technique [0002] Menthol (also known as menthol and peppermint oil) has a special aroma, spicy and cooling sensation. As one of the most sold spices in the world, menthol is widely used in the food industry, daily fine chemicals, medicine and health, etc. [0003] Menthol has 3 chiral centers, and there are 8 stereoisomers in total. Among them, L-menthol has a light and sweet pungent smell and has a strong cooling effect; D-menthol has a pungent pungent smell and almost no cooling effect. effect. Due to the high application value of levomenthol, all of them are basically levomenthol in the market. It is widely used in cigarettes, cosmetics, toothpaste, chewing gum, sweets and refreshing drinks, medicines and linimen...

Claims

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Application Information

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IPC IPC(8): C07C35/12C07C29/17
Inventor 王三永李春荣王林杨定乔
Owner GUANGDONG FOOD IND INST
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