Preparation method of trans-ketone intermediate

Abstract

The invention discloses a preparation method of trans-ketone intermediates. The trans-ketone intermediates comprise compounds as shown in a formula (I) and a formula (II). The preparation process comprises the following steps: (1) performing catalytic hydrogenation on the compounds as shown in the formula (I) to prepare ketone intermediate products; (2) preparing a Grignard reagent from benzyloxy halogenated benzene and magnesium powder, and performing acidolysis dehydration on the Grignard reagent and the ketone intermediate product prepared in the step (1) to obtain a compound as shown in a formula (II); and (3) carrying out catalytic hydrogenation and isomerization reaction on the compound as shown in the formula (II) prepared in the step (2). According to the preparation method provided by the invention, the technical problem that multiple benzyl alcohol impurities and impurity products after ketone condensation exist in acidolysis dehydration products of dicyclohexanone ethylene monoketal adopted in a traditional process is solved, and the purification difficulty of trans-ketone intermediate products is greatly reduced.

Description

technical field [0001] The invention belongs to the technical field of liquid crystal intermediate synthesis, and in particular relates to a preparation method of trans ketone intermediates. Background technique [0002] In the liquid crystal material industry, trans-4’-(4-methylphenyl)(1,1’-bicyclohexyl)-4-one is the production (referred to as vinyl monomer) and (referred to as butene monomer) and other important raw materials for monomer compounds. The two are applied in large quantities in STN mixed crystal and TFT mixed crystal formulations. [0003] The Japanese patent with publication number JP2014162752A relates to a preparation route of trans-4'-(4-methylphenyl)(1,1'-bicyclohexyl)-4-one, as follows: [0004] [0005] Among them, methyl bromide and magnesium flakes are prepared in anhydrous tetrahydrofuran to prepare Grignard reagent, and further react with dicyclohexanone ethylene glycol monoketal to prepare benzyl alcohol; then use p-toluenesulfonic acid to ...

AI Technical Summary

Problems solved by technology

[0010] Its preparation process involves steps such as hydrogenation, oxidation, and selective protection of diols, making batch production and purification more cumbersome

In particular, the reaction selectivity of dihydric alcohol monoprotection is 80%. If the requirement of purity higher than 99.5% is to be achieved in actual production, the single-pass yield will drop below 60%, and the raw materials diketone and diethylene glycol will be purified and removed. The by-product process of alcohol protection is relatively cumbersome, and there are few high-quality manufacturers of this raw material, so there are not many options for purchasing

[0011] In addition, hydrolysis (acidolysis) after the reaction of 4-methylbromophenyl Grignard reagent with dicyclohexanone ethylene glycol monoketal will produce a small amount of deprotected product Prepared in further dehydration reaction A series of benzyl alcohol impurities and ketone condensation impurities are produced or remain in the intermediate product, which will cause more than dozens of residual impurities of known and unknown structures in the intermediate product, such as: (cis-trans mixture), (cis-trans mixture), (cis-trans mixture), (cis-trans mixture) Etc., these inherent impurity crystals are difficult to remove, reducing the purity of the product

[0012] Furthermore, the traditional route to remove ethylene glycol protection uses concentrated formic acid reaction, which can be nearly completely removed, but this will lead to a large amount of waste formic acid, and other inorganic acids in the system will produce more ketones due to the strong acidic environment By-product impurities

In addition, the incomplete removal of ethylene glycol protection will also cause unreacted raw material residues to enter the next step and become larger impurities, which will affect the purification effect.

[0013] In summary, the preparation process route of trans-4'-(4-methylphenyl)(1,1'-bicyclohexane)-4-one and similar ketone intermediates in the prior art is relatively long, And the inherent impurities produced therein are not easy to remove, which affects the quality of the final product

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