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Method for preparing optically-pure L-menthone and catalyst for the method

A technology of menthone and catalyst, which is applied in the field of preparing optically pure L-menthone method and related catalysts, can solve the problems of limited turnover increase, adverse environmental impact, short catalyst life, etc., and achieve the effect of increasing life

Active Publication Date: 2019-05-03
WANHUA CHEM GRP CO LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

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 DE4236111A1 reported the method of obtaining L-menthone by dehydrogenation reaction using L-menthol as raw material under the action of Cu-based catalyst, but this process must use optically pure L-menthol as raw material to obtain optically pure L-menthol. - Menthone

Method used

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  • Method for preparing optically-pure L-menthone and catalyst for the method
  • Method for preparing optically-pure L-menthone and catalyst for the method
  • Method for preparing optically-pure L-menthone and catalyst for the method

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Experimental program
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Effect test

Embodiment 1

[0058] Under an argon atmosphere, 26.1 mg of salen manganese compound (1) (4-tBu-Salen Mn, purchased from Aldrich Company), 15.42 g of racemic menthol (ee=0%, L-menthol / D-menthol= 1:1 (mol)) was dissolved in 15mL of acetonitrile, and transferred to a 50mL reactor, started stirring, cooled to 0°C, slowly added 5.7g of 30% hydrogen peroxide solution dropwise, reacted at 0°C for 1h, and used gas chromatography The measured L-menthol conversion rate is 99.9%, the product is L-menthone, the optical purity is 99ee%, and the yield of L-menthone is 99.8% based on the L-menthol in the raw material.

Embodiment 2

[0060] Dissolve 32mg of salen manganese compound (1) and 15.42g of L-menthol (ee=98%) in 15mL of acetonitrile under an argon atmosphere, and transfer them to a 50mL reactor, start stirring, cool down to 0°C, and slowly add 17g of 30% hydrogen peroxide solution was reacted at 0°C for 3 hours, and the conversion rate of L-menthol was measured by gas chromatography to be 99.9%, and the product was L-menthone with an optical purity of 99ee%. The yield of L-menthone was calculated to be 99.8%.

Embodiment 3-5

[0062] Under an argon atmosphere, the salen manganese compounds (4-tBu-2-Me-Salen Mn(2), 2,4-di-tBu-Salen Mn(3), 4- Naphthalen-Salen Mn (4) purchased from Aldrich Company) 0.05mmol, 15.22g racemic menthol (ee=0%, L-menthol / D-menthol=1:1 (mol)) was dissolved in 15mL acetonitrile, and transferred to a 50mL reaction kettle, started stirring, cooled to 0°C, slowly added 5.7g of 30% hydrogen peroxide solution dropwise, and reacted for 5h at 0°C, used gas chromatography to measure the conversion rate of L-menthol in the raw materials and the See Table 1 for the yield of L-menthone in terms of L-menthol and the optical purity of product L-menthone.

[0063] Table 1 Reaction conditions and results

[0064]

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Abstract

A method for prepare optically-pure L-menthone and a catalyst for the method are provided. Under the action of oxidation catalyst, L-menthol in menthol is selectively oxidized to prepare the optically-pure L-menthone. The oxidation catalyst comprises a chiral salen manganese compound and hydrogen peroxide. High stereoselectivity synthesis of L-menthone is realized and the optical purity of the product can reach 99 ee%.

Description

technical field [0001] The invention relates to a method for preparing optically pure L-menthone and related catalysts, in particular to a method for selectively catalyzing L-menthol to prepare optically pure L-menthone and a catalyst for the method. 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: L-menthone and D-menthone, which are mainly used to prepare mint flavors. Naturally extracted menthone is in the L-configuration, so the synthesis of L-menthone has always been received 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 ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C49/407C07C45/29B01J31/22
CPCY02P20/584
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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