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Method for chiral synthesis of levorotatory menthol

A technology for chiral synthesis of L-menthol, applied in chemical instruments and methods, preparation of organic compounds, preparation of hydroxyl compounds, etc., can solve the problems of complex and harsh processes, low overall yield, poor selectivity, etc., and achieve Good selectivity, simple recovery and simple synthesis process

Active Publication Date: 2011-04-13
GUANGDONG FOOD IND INST +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, this route has poor selectivity, complex and harsh process, and low overall yield.

Method used

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  • Method for chiral synthesis of levorotatory menthol
  • Method for chiral synthesis of levorotatory menthol
  • Method for chiral synthesis of levorotatory menthol

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0035] 1. Preparation of catalyst

[0036] (1) Catalyst precursor [Rh(COD)Cl] 2 Synthesis

[0037] Add rhodium trichloride trihydrate (2.0g, 7.6mmol) into a 150mL three-necked flask. After putting in a magnetic stir bar, add 95% ethanol (30mL), water (12mL) and 1,5- Cyclooctadiene (6mL, 49mmol), stirred and refluxed for 24h, formed orange-yellow precipitate, cooled to room temperature, filtered, the product was washed with cold methanol-water mixture to remove unreacted 1,5-cyclooctadiene, and then used A little cold ether was used to infiltrate the solid, and then vacuum dried at 25°C for 8 hours. Remove the solvent to obtain orange-yellow crystals [Rh(COD)Cl] 2 (1.593g, yield 85%) m.p. 243°C.

[0038] (2) Catalyst [Rh((S)-p-Tol-BINAP) 2 ]BF 4 Preparation

[0039] Under the protection of nitrogen, add 0.123g (0.25mmol) [Rh(COD)Cl] to a 25mL round bottom flask 2 And 0.339g(0.5mmol)(S)-p-Tol-BINAP, add 5.0mL freshly steamed CH 2 Cl 2 Dissolve the solid, put in a magnetic stir bar, and...

Embodiment 2

[0047] 1. Preparation of catalyst

[0048] (1) Catalyst precursor [Rh(COD)Cl] 2 Synthesis

[0049] Add rhodium trichloride trihydrate (1.0g, 3.8mmol) and anhydrous potassium carbonate (0.55g, 4mmol) into a 100mL three-necked flask, add 95% ethanol (17mL) and water (8.5mL) under nitrogen protection And 1,5-cyclooctadiene (3mL, 24.5mmol), put in a magnetic stirrer, stir at reflux for 24h, produce orange-yellow precipitate, cool to room temperature, filter, the product is washed with cold methanol-water mixture to remove unreacted 1,5-cyclooctadiene, and finally infiltrate the solid with a little cold ether, and then vacuum dry at 25℃ for 8h, remove the solvent, and obtain an orange-yellow product [Rh(COD)Cl] 2 (0.778g, yield 83%) m.p. 242°C.

[0050] (2) Catalyst [Rh((S)-BINAP) 2 ]BF 4 Preparation

[0051] Under the protection of nitrogen, add 0.15g (0.3mmol) [Rh(COD)Cl] to a 10mL round bottom flask 2 , 3mL freshly distilled tetrahydrofuran and 70% 2.5mL HBF 4 , Add 1,5-cyclooctadiene ...

Embodiment 3

[0059] 1. Preparation of catalyst

[0060] (1) Catalyst precursor [Rh(COD)Cl] 2 Synthesis

[0061] Add rhodium trichloride trihydrate (0.5g, 1.9mmol) into a 50mL three-necked flask, add 95% methanol (9mL), water (4mL) and 1,5-cyclooctadiene (0.14g) under nitrogen , 122mmol), put in a magnetic stirrer, stirred and refluxed for 24h to produce orange-yellow precipitate, cooled to room temperature, filtered, the product was washed with cold methanol-water mixture to remove unreacted 1,5-cyclooctadiene, and finally used A little cold ether soaks the solid, then vacuum-drys at 25℃ for 8h, removes the solvent, and recrystallizes with dichloromethane / ether to obtain an orange-yellow product [Rh(COD)Cl] 2 (0.393g, yield 84%) m.p. 243°C.

[0062] (2) Catalyst [Rh((S)-XylBINAP) 2 ]BF 4 Preparation

[0063] Under the protection of nitrogen, add 0.47g (0.95mmol) [Rh(COD)Cl] to a 10mL round bottom flask 2 Add 0.209g (1.9mmol) NaBF 4 , Put in a magnetic stir bar, add 3mL of tetrahydrofuran to disso...

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Abstract

The invention discloses a method for chiral synthesis of levorotatory menthol. In the process, dextrorotatory pulegone is used as a starting material; catalytic hydrogenation is carried out on the dextrorotatory pulegone by a chiral rhodium catalyst to generate levorotatory menthone; and the catalytic hydrogenation is carried out on the levorotatory menthone by a chiral ruthenium catalyst to synthesize the levorotatory menthol. In the process for synthesizing the levorotatory menthol through an asymmetric synthesis technology, the yield of the levorotatory menthone is more than 90%, the ee value of the levorotatory menthone is more than 99%, the total yield of the levorotatory menthol is greater than 83%, the ee value of the levorotatory menthol is greater than 98%, and the specific rotation is from-49 degrees to -50 degrees. The synthetic process is simple and is suitable for industrial production of the levorotatory menthol in a large scale, and the prepared levorotatory menthol hasthe advantages of high yield, good selectivity, high catalyst activity and other characteristics, is simple to recover.

Description

Technical field [0001] The invention belongs to the technical field of organic chemistry chiral synthesis, and specifically relates to a method for chiral synthesis of L-menthol by two-step reaction using dextropulegone as a raw material. Background technique [0002] Menthol (also known as menthol and peppermint oil) has a special fragrance, pungency and coolness. As one of the world's most sold spices, it is widely used in the food industry, daily fine chemicals, and medicine and hygiene. Such as toothpaste, food, tobacco, alcohol, refreshing beverages, cosmetics, soaps; widely used in medicine to drive wind, antiseptic, anti-inflammatory, analgesic, antipruritic, stomach and other medicines. Levomenthol has three chiral centers, therefore, there are 8 stereoisomers, but among these 8 stereoisomers, only Levomenthol (l-menthol) has higher economic value. It has a brisk and sweet irritating smell and has a strong cooling effect. The cooling effect mechanism is to stimulate the ...

Claims

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Application Information

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IPC IPC(8): C07C35/12C07C29/145
Inventor 王三永李春荣段泽斌杨定乔
Owner GUANGDONG FOOD IND INST
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