Method for preparing R-citronellal

Abstract

The invention provides a method for preparing R-citronellal. The catalytic activity and stability of a catalyst can be remarkably improved based on the method provided by the invention, so a higher cumulative conversion number is realized. According to the method for preparing R-citronellal provided by the invention, a reaction substrate is subjected to an asymmetric hydrogenation reaction in thepresence of a transition metal catalyst to generate R-citronellal; the reaction substrate is selected from neryl aldehyde and / or geranial, and the transition metal catalyst is obtained through a reaction of a transition metal compound capable of being dissolved in a reaction system and an optically active ligand containing two phosphorus atoms; and before the reaction substrate is put into the reaction system of the asymmetric hydrogenation reaction, the reaction substrate is pretreated by using aluminosilicate and / or nano-silver, and filtering is conduced to remove the aluminosilicate and / ornano-silver after pretreatment.

Description

technical field [0001] The invention relates to the technical field of R-citronellal preparation, in particular to a method for preparing R-citronellal by asymmetrically hydrogenating neral and / or geranial. Background technique [0002] Citronellal is a compound with a chiral center, because R-citronellal is an important intermediate for the synthesis of L-menthol, so its preparation method, especially low-cost, large-scale industrial preparation method has the advantages of Significance. [0003] Adv.Synth.Catal., 2003, 345 (1): 15-32 has reported that Takasago Company takes myrcene as raw material, obtains the method for R-citronellal through three-step reaction, and its core technology is the non-toxicity of allylamine Symmetrical isomerization, this process step is long, needs to use a large amount of lithium reagents. [0004] EP 0000315 reports a process for the preparation of optically active R-citronellal by hydrogenating geranial or neral in the presence of a cata...

AI Technical Summary

Problems solved by technology

The use of this catalyst can effectively improve product chemistry and stereoselectivity, but there are disadvantages of low hydrogenation efficiency, especially under the condition of high substrate / catalyst, the conversion frequency of the catalyst is significantly reduced, resulting in the need for multiple recycling of the catalyst and complicated process operations , and the catalyst life is short, prone to noble metal coupling deactivation and other disadvantages

[0007] In summary, although there have been many reports on the asymmetric reduction of citral to obtain R-citronellal, most of these reports have the disadvantages of low hydrogenation efficiency and large amount of catalyst, especially in high substrate / catalyst Under certain conditions, the reaction rate is significantly reduced; after the reaction, the catalyst either cannot be recovered, or the recovery conditions are harsh and the process is complicated, so the economic cost is high and the benefit is poor

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