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Method for chiral synthesis of levorotatory menthol

A technology for levomenthol and chiral synthesis, which is applied in chemical instruments and methods, preparation of organic compounds, preparation of hydroxy compounds, etc., can solve the problems of low total yield, complex and harsh process, poor selectivity and the like, and achieves The effect of simple recovery, good selectivity and simple synthesis process

Active Publication Date: 2013-06-12
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. Catalyst Preparation

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

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

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

[0039] Under nitrogen protection, add 0.123g (0.25mmol) [Rh(COD)Cl] in a 25mL round bottom flask 2 and 0.339g (0.5mmol) (S)-p-Tol-BINAP, add 5.0mL freshly distilled CH 2 Cl 2 The solid was dissolved, placed...

Embodiment 2

[0047] 1. Catalyst Preparation

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

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

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

Embodiment 3

[0059] 1. Catalyst preparation

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

[0061] Add rhodium trichloride trihydrate (0.5g, 1.9mmol) in a 50mL three-necked flask, add 95% methanol (9mL), water (4mL) and 1,5-cyclooctadiene (0.14g , 122mmol), put into a magnetic stirrer, stir and 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 use Soak the solid with a little cold ether, then dry it in vacuum at 25°C for 8h, remove the solvent, and recrystallize with dichloromethane / ether to obtain the orange-yellow product [Rh(COD)Cl] 2 (0.393 g, 84% yield) m.p. 243°C.

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

[0063] Under nitrogen protection, add 0.47g (0.95mmol) [Rh(COD)Cl] to a 10mL round bottom flask 2 Add 0.209g (1.9mmol) NaBF 4 , put into a magnetic stirrer, add 3mL tetrahydrofuran to dissolve and quic...

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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 chiral synthesis of organic chemistry, and in particular relates to a method for chirally synthesizing L-menthol with D-pulegone as a raw material through two-step reactions. Background technique [0002] Menthol (also known as menthol and peppermint oil) has special aroma, pungent and cool feeling. As one of the largest-selling spices in the world, it is widely used in food industry, daily fine chemical industry, medicine and hygiene, etc. Such as toothpaste, food, tobacco, wine, cool drinks, cosmetics, and soap; it is widely used in medicine for carminative, antiseptic, anti-inflammatory, analgesic, antipruritic, and stomach-invigorating drugs. Levomenthol has three chiral centers, so there are 8 stereoisomers, but among these 8 stereoisomers, only Levomenthol (l-menthol) has high economic value. It has a light and sweet pungent smell and has a strong cooling effect. The mechanism of the cooling effect...

Claims

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Application Information

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Patent Type & Authority Patents(China)
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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