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Method for preparing L-menthone

A technology of menthone and isopulegol, which is applied in the field of selectively catalyzing L-isopulegol to prepare L-menthone, can solve the problems of limited turnover increase, adverse environmental impact, and increased process complexity, achieving increased The effect of longevity

Active Publication Date: 2019-04-19
WANHUA CHEM GRP CO LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the improvement in the turnover number (TON) of this process is limited, the catalyst life is still short, and a large amount of phenol derivatives is required, which will have adverse effects on post-processing and the environment
At the same time, this process can not solve the problem of poor optical purity of L-menthone, which increases the complexity of the whole process
[0010] Patent CN 107602357 A discloses a method for preparing menthone by hydrogen transfer of isopulegol by adding a small amount of auxiliary agent using a transition metal complex as a homogeneous catalyst, which has high conversion rate, selectivity and high turnover number ( TON), but this process can not obtain optically pure L-menthone

Method used

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  • Method for preparing L-menthone

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Experimental program
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Effect test

Embodiment 1

[0059] 41.4mg (0.1mmol) bisphosphine ligand (chiral phosphine ligand compound (1)), 20.7mg (0.1mmol) RuCl 3 Dissolved in 15mL toluene, and transferred to a 50mL reaction kettle, 30.44g (0.2mol) racemic isopulegol (ee=0%, L-isopulegol / D-isopulegol=1:1 (mol)) was injected into the reaction kettle, and the pressure was adjusted to 1 bar after passing through the gas in the nitrogen replacement kettle for three times. Start stirring and react at 150°C for 10 hours. The conversion rate of L-isopulegol is 99.9% as measured by gas chromatography, and the conversion of D-isopulegol does not occur. The product is L-menthone with an optical purity of 99ee%. , no isomenthone is generated, and the yield of L-menthone is 99.8% based on the L-isopulegol in the raw material.

Embodiment 2

[0061] 82.8mg (0.2mmol) bisphosphine ligand (chiral phosphine ligand compound (1)), 41.4mg RuCl 3 (0.2mmol) was dissolved in 15mL of toluene, and transferred to a 50mL reaction kettle, 15.22g L-isopulegol (ee=98%) was injected into the reaction kettle, and the pressure was adjusted to 50 after passing through the gas in the nitrogen replacement kettle for three times. bar. Start stirring and react at 150°C for 10 hours. The conversion rate of L-isopulegol is 99.9% as measured by gas chromatography, and the conversion of D-isopulegol does not occur. The product is L-menthone with an optical purity of 99ee%. , no isomenthone is generated, and the yield of L-menthone is 99.8% based on the L-isopulegol in the raw material.

Embodiment 3

[0063] 165.6mg (0.4mmol) bisphosphine ligand (chiral phosphine ligand compound (1)), 20.7mg (0.1mmol) RuCl 3 Dissolve in 15mL toluene and transfer to a 50mL reactor, inject 30.44g (0.2mol) L-isopulegol (ee=50%) into the reactor, pass through nitrogen to replace the gas in the reactor for three times and then adjust the pressure to 1 bar. Start stirring and react at 150°C for 10 hours. The conversion rate of L-isopulegol is 99.9% as measured by gas chromatography, and the conversion of D-isopulegol does not occur. The product is L-menthone with an optical purity of 99ee%. , no isomenthone is generated, and the yield of L-menthone is 99.8% based on the L-isopulegol in the raw material.

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Abstract

The invention provides a method for preparing L-menthone. The method starts from isopulegol containing L-isopulegol, and prepares L-menthone through a method for selectively catalyzing the L-isopulegol to generate hydrogen transfer. The method has advantages of being simple in operation, low in catalyst cost, high in product yield and less in three wastes (waste gas, waste water and industrial residue); through a technology of hydrogenation transfer, the using of hydrogen is not needed, so that the method has better technology safety, and is suitable for industrial production application. TheL-menthone can be performed by performing selective hydrogen transfer on the L-isopulegol in the isopulegol under the action of a transition metal catalyst through the provided method; and the transition metal catalyst includes a transition metal compound and a chiral phosphine ligand.

Description

technical field [0001] The invention relates to a method for preparing L-menthone, in particular to a method for selectively catalyzing L-isopulegol to prepare L-menthone. Background technique [0002] Menthone, also known as menthone, has the cool and characteristic aroma of natural mint. Menthone exists in the form of two stereoisomers: menthone and isomenthone, each of which exists in the form of two enantiomers, is mainly used to prepare mint-type flavors, so the synthesis of menthone has always been subject to people's attention. [0003] At present, menthone products include natural menthone and synthetic menthone. [0004] Natural menthone is mainly extracted from natural raw materials such as mint, geranium, and bluestem through rectification, and its price and supply are significantly affected by raw materials. [0005] There are many ways to synthesize menthone, mainly based on the oxidation of menthol, using stoichiometric oxidation systems such as chromate, pe...

Claims

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Application Information

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IPC IPC(8): C07C45/51C07C49/407B01J31/24
CPCC07C45/512B01J31/2404C07C2601/14C07C49/407
Inventor 董菁李鹏刘春东方文娟王联防张永振王明永黎源
Owner WANHUA CHEM GRP CO LTD
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