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A kind of method for preparing optically pure 1-menthone and catalyst for the method

A technology of menthone and oxidation catalyst, which is applied in the direction of physical/chemical process catalysts, chemical instruments and methods, and oxidation to prepare carbonyl compounds, etc., which can solve the problems of limited turnover increase, short catalyst life, and adverse environmental effects, etc., to increase life , high stability, high activity and stable effect

Active Publication Date: 2022-07-12
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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  • A kind of method for preparing optically pure 1-menthone and catalyst for the method
  • A kind of method for preparing optically pure 1-menthone and catalyst for the method
  • A kind of method for preparing optically pure 1-menthone and catalyst for the method

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Effect test

Embodiment 1

[0058] Under 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 15 mL of acetonitrile, transferred to a 50 mL reaction kettle, turned on stirring, cooled to 0 °C, slowly added dropwise 5.7 g of 30% hydrogen peroxide solution, reacted at 0 °C for 1 h, and then used gas chromatography The conversion rate of L-menthol was measured to be 99.9%, the product was L-menthone, the optical purity was 99ee%, and the yield of L-menthol was 99.8% based on the L-menthol in the raw material.

Embodiment 2

[0060] Under an argon atmosphere, 32 mg of salen manganese compound (1) and 15.42 g of L-menthol (ee=98%) were dissolved in 15 mL of acetonitrile, transferred to a 50 mL reaction kettle, stirred, cooled to 0 °C, and slowly added dropwise. 17 g of a 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%. The product was L-menthone, and the optical purity was 99ee%. The yield of L-menthone was 99.8%.

Embodiment 3-5

[0062] Under argon atmosphere, the salen manganese compounds of structural formula (2)-(4) (4-tBu-2-Me-SalenMn(2), 2,4-di-tBu-SalenMn(3), 4- Naphthalen-Salen Mn (4) was 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, turned on stirring, cooled to 0°C, slowly added dropwise 5.7g of 30% hydrogen peroxide solution, reacted at 0°C for 5h, and used gas chromatography to measure the conversion rate of L-menthol in the raw materials and the ratio of the raw materials to the raw materials. The yield of L-menthol in the L-menthol and the optical purity of the product L-menthone are shown in Table 1.

[0063] Table 1 Reaction conditions and results

[0064]

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Abstract

The present invention provides a method for preparing optically pure L-menthone and a catalyst for the method. Under the action of an oxidation catalyst, L-menthol in menthol is selectively oxidized to prepare optically pure L-menthone. The oxidation catalyst includes a chiral salen manganese compound and hydrogen peroxide. The high stereoselectivity synthesis of L-menthone was achieved, and the optical purity of the product could be as high as 99ee%.

Description

technical field [0001] The invention relates to a method for preparing optically pure L-menthone and a related catalyst, 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 cooling 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 L-configuration, so the synthesis of L-menthone has always been get people's attention. [0003] At present, menthone products include natural menthone and synthetic menthone. [0004] Natural menthone is mainly obtained by rectifying and extracting natural raw materials such as natural mint, geranium, and Miscanthus, and its price and supply are significantly affected by the raw materials. [0005] There are many methods for synthesizing menthone, mainly ...

Claims

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Application Information

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Patent Type & Authority Patents(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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