Preparation method of optically active citronellal

Abstract

The invention provides a preparation method of optically active citronellal, which can obviously enhance the catalytic stability of an optically active transition metal catalyst for asymmetric hydrogenation for homogeneous catalysis, thereby implementing higher turnover number. In the preparation method of the optically active citronellal, a substrate is subjected to an asymmetric hydrogenation reaction in the presence of the transition metal catalyst to generate the optically active citronellal, and the transition metal catalyst is obtained by reacting a transition metal compound with an optically active ligand containing two phosphorus atoms, wherein the substrate raw material is one or a combination of two of neral and geranial, and the hydroxyl value in the substrate raw material for the asymmetric hydrogenation reaction is controlled to be less than or equal to 6mgKOH / g and / or the iron content is controlled to be less than or equal to 50ppm.

Description

technical field [0001] The invention relates to a method for preparing optically active citronellal, in particular to a method for preparing optically active citronellal, especially R-citronellal, by asymmetrically hydrogenating neral and / or geranial. Background technique [0002] Citronellal is an important fragrance ingredient, widely used in the flavoring and preparation of beverages, candies, food, etc. It is also an important intermediate compound, especially optically active citronellal is an important intermediate used to synthesize L-menthol. [0003] EP 0000315 discloses a process for the preparation of optically active R-citronellal by hydrogenating geranial or neral in the presence of a catalyst complex dissolved in the reaction system and consisting of rhodium and a chiral phosphine composition. [0004] J.Mol.Cat.16(1982)51-59 and Helv.Chim.Acta.84(2001)230-242 reported the homogeneous catalytic hydrogenation of α,β-unsaturated aldehydes and used this method t...

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Problems solved by technology

[0006] The method reported above has the advantages of high chemoselectivity and stereoselectivity, but the homogeneous transition metal catalysts prepared by transition metal compounds and chiral ligands have the disadvantage of low hydrogenation efficiency, especially at high molar ratios of substrate / Under the conditions of the catalyst, the conversion frequency of the catalyst is significantly reduced, resulting in the need for multiple recycling of the catalyst, complex process operations, and the catalyst is prone to problems such as metal coupling deactivation, and the turnover number is low. When applied on an industrial scale, the cost of the catalyst is high.

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