Method for synthesizing L-menthol

A synthesis method and menthol technology, applied in the synthesis field of L-menthol, can solve the problems of difficult industrial application, complicated process, low yield and the like, and achieve the effects of high yield, simple process and low price

Inactive Publication Date: 2009-12-16
SHANGHAI WANXIANG FLAVORS & FRAGRANCES
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0006] The general chemical synthesis process can only obtain racemic menthol, and often needs to obtain L-menthol by chiral resolution or other means, which has defects such as complex process and low yield; while the process adopted in C...

Method used

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  • Method for synthesizing L-menthol
  • Method for synthesizing L-menthol

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Embodiment 1

[0023] The synthesis of embodiment 1 L-menthol

[0024] 1. Amination reaction.

[0025] Replace the 1L three-necked bottle equipped with electromagnetic stirring, reflux condenser, constant pressure dropping funnel, suction head and thermometer into a nitrogen atmosphere, and add freshly steamed myrcene (80%, 82-84 ° C / 4mmHg, 173.3g, 218mL, 1.02mol), diethylamine (140g, 200mL, 1.91mol), slowly add n-BuLi (93mL, 2.2M in ether, 0.205mol, 20mol%) dropwise under stirring, and add dropwise for 70min After completion, the water bath was heated to 60° C. and stirred for 7 hours, then the heating was stopped, and the system was allowed to return to room temperature naturally, and slowly poured into 1 L of ice water, stirring continuously during this period. The layers were separated, the aqueous phase was extracted with ether (3×300 mL), the organic phases were combined, washed with 500 mL of water, and dried over anhydrous sodium sulfate. The desiccant was removed by suction filt...

Embodiment 2

[0042] The synthesis of embodiment 2 L-menthol

[0043] 1. Amination reaction.

[0044] Replace the 1L three-necked bottle equipped with electromagnetic stirring, reflux condenser, constant pressure dropping funnel, suction head and thermometer into a nitrogen atmosphere, and add freshly steamed myrcene (80%, 82-84 ° C / 4mmHg, 173.3g, 218mL, 1.02mol), diethylamine (140g, 200mL, 1.91mol), slowly add n-BuLi (46mL, 2.2M in ether, 0.102mol, 10mol%) dropwise under stirring, and add dropwise for 50min After completion, the water bath was heated to 50° C. and stirred for 6 h, then the heating was stopped, and the system was allowed to return to room temperature naturally, and slowly poured into 1 L of ice water, while stirring continuously. The layers were separated, the aqueous phase was extracted with ether (3×300 mL), the organic phases were combined, washed with 500 mL of water, and dried over anhydrous sodium sulfate. The desiccant was removed by suction filtration, and dieth...

Embodiment 3

[0061] The synthesis of embodiment 3 L-menthol

[0062] 1. Amination reaction.

[0063] Replace the 1L three-necked bottle equipped with electromagnetic stirring, reflux condenser, constant pressure dropping funnel, suction head and thermometer into a nitrogen atmosphere, and add freshly steamed myrcene (80%, 82-84 ° C / 4mmHg, 173.3g, 218mL, 1.02mol), diethylamine (140g, 200mL, 1.91mol), slowly add n-BuLi (93mL, 2.2M in ether, 0.205mol, 20mol%) dropwise under stirring, add dropwise for 50min After completion, the water bath was heated to 50° C. and stirred for 5.5 hours, then the heating was stopped, and the system was allowed to return to room temperature naturally, and slowly poured into 1 L of ice water, stirring continuously during this period. The layers were separated, the aqueous phase was extracted with ether (3×300 mL), the organic phases were combined, washed with 500 mL of water, and dried over anhydrous sodium sulfate. The desiccant was removed by suction filtra...

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Abstract

The invention belongs to the technical field of organic synthesis, in particular to a method for synthesizing L-menthol. The method for synthesizing L-menthol takes myrcene as an initial raw material and comprises the following steps: amination reaction: diethylamine and myrcene carry out amination reaction to obtain geranylamine; isomerization reaction: the geranylamine carries out isomerization reaction under the catalytic action of chiral catalyst to obtain intermediate enamine; hydrolysis reaction: the enamine carries out hydrolysis reaction in an acidic medium to produce intermediate D-citronellal; cyclization reaction: the D-citronellal generates L-isopulegol by lewis acid catalyst and organic solvent; and hydrogenation reaction: the L-isopulegol is hydrogenated to obtain L-menthol. The method for synthesizing L-menthol has the yield of more than 90 percent, the GC purity of higher than 99.0 percent and the specific rotation of -49 degrees to -50 degrees, the raw material myrcene has wide sources and lower cost, and the whole method has simple technology, good repeatability and high yield and is quite suitable for large-scale industrialized production.

Description

technical field [0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a synthesis method of L-menthol. Background technique [0002] As a naturally occurring cyclic flower enol, L-menthol, one of the main components of peppermint oil, occupies a special place due to its cooling and clearing effects. Therefore L-menthol can be used as a spice or flavoring agent, and can be used in the pharmaceutical industry. Preparation of menthol by catalytic hydrogenation of a compound having at least one double-bonded menthane carbon backbone substituted by an oxygen at the 3-position (e.g. thymol) yields a mixture of 8 optically active menthols: D,L-menthol , D, L-isomenthol, D, L-neomenthol and D, L-neomenthol. These 8 optically active menthols differed in their sensory properties, with only L-menthol having the characteristic minty smell and the aforementioned refreshing effect. L-menthol is therefore the most valuable menthol stereoi...

Claims

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Application Information

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IPC IPC(8): C07C35/12C07C29/17C07C29/56C07B53/00B01J31/02
Inventor 金鹏黄战鏖陈兆刚陈文昌张金宝张长征
Owner SHANGHAI WANXIANG FLAVORS & FRAGRANCES
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