1. Extraction and synthesis of natural grade raspberry ketone
Due to the continuous strengthening of people’s awareness of environmental protection, in recent years, the international market has favored natural fragrance products. Using the natural plant raspberry as the starting material, the natural grade raspberry ketone is obtained through the steps of extraction, decolorization, concentration, and refining; using natural anisaldehyde and fermented acetone as the starting material, through the Claisen-Schmidt reaction and selective hydrogenation , demethylation reaction to obtain natural raspberry ketone, the total yield is 75.75% (calculated as anisaldehyde), the content is 98.65%, and the aroma is pure; natural anisaldehyde is used as raw material, and natural acetone produced by fermentation is condensed Anisecetone is obtained, and anisecetone is obtained by hydrogenation. Finally, anisecetone is subjected to demethylation reaction to obtain natural raspberry ketone, and its natural degree is determined to be over 98% by measuring isotope 14C.
In addition, such methods are also reported in many patents. At present, the synthesis process of natural grade raspberry ketone is relatively mature, but the cost is high and the yield needs to be improved. It is limited to the use of high-end products, and further exploration of lower cost and more effective synthesis methods is needed.
2. Synthesis of petrochemical-grade raspberry ketones
As the total demand for raspberry ketone in the world increases year by year, and the raw materials of natural-grade raspberry ketone are limited and expensive, which cannot meet the needs of ordinary consumers, so plant extraction is uneconomical; and raspberry ketone synthesized from petrochemical raw materials Due to the rich source of raw materials and low price, it is widely used in the field of daily chemical essence deployment and agriculture. At present, raspberry ketone mainly comes from synthesis. From the perspective of starting materials, petrochemical grade raspberry ketone mainly includes p-hydroxybenzaldehyde and acetone as raw materials, phenol and 4-butanol-2-one as raw materials, and phenol and methyl vinyl ketone as raw materials.
1) Using p-hydroxybenzaldehyde and acetone as raw materials
Under base catalysis, 4-p-hydroxyphenyl-3-buten-2-one was synthesized by Claisen-Schmidt condensation through orthogonal experiment optimization process (yield 88.4%), and continued hydrogenation under palladium-carbon catalysis to synthesize Basinone (yield 84.0%); using NaOH solution as the Claisen-Schmidt condensation catalyst to synthesize p-hydroxyphenyl-3-buten-2-one, and then using 5% Pd/C and nickel formate as the second step reaction Catalyst, the raspberry ketone yield that obtains is respectively 72.55% and 65.7%.
Research the condensation reaction conditions of 4-Hydroxybenzaldehyde and acetone with orthogonal test, obtain preferred process condition as: the amount ratio n (p-Hydroxybenzaldehyde) of material substance: n (acetone): n (NaOH)=1.0: 25: 25 (reaction at 30 ℃ for 5 h), and then conventional hydrogenation reduction, vacuum distillation, and mixed solvent recrystallization to obtain raspberry ketone (yield 61.8%); using p-hydroxybenzaldehyde and acetone as raw materials, using NaOH to catalyze Claisen -Schmid condensation reaction, then using nickel formate as catalyst and isopropanol as solvent, hydrogenation reduction to obtain raspberry ketone (yield 42.0%).
2) Using phenol and 4-butanol-2-one as raw materials
Using acetone and formaldehyde as raw materials to synthesize the intermediate 4-butanol-2-one, and then using concentrated sulfuric acid as a catalyst to make it condense with phenol, purify, and synthesize raspberry ketone in two steps (the yield is more than 70%) ; Adopt phenol and 4-butanol-2-ketone under the catalysis of strongly acidic solid acid, one-step synthetic raspberry ketone product (yield 92.5%, purity 99%); Take formaldehyde and acetone as raw material, immobilized base KF/ A12O3 was used as catalyst to synthesize butanone alcohol, then butanone alcohol was reacted with phenol, and ion exchange resin D218 was used as catalyst to synthesize crude raspberry ketone (yield 46.0%~71.0%).
A θ-ring stainless steel packed fixed bed reactor was used to synthesize butanone alcohol with formaldehyde and acetone as raw materials and NaOH as a catalyst, and then butanone alcohol and phenol were used as raw materials to adopt a fluidized bed reactor with ion exchange resin D218 as a catalyst. Synthesis of raspberry ketone; use phenol and 4-hydroxy-2-butanone as raw materials, carry out Claisen-Schmidt condensation reaction to synthesize 4-(4-hydroxyphenyl)-3-buten-2-one, and then in acid catalysis Under Friedel-Crafts alkylation reaction to obtain raspberry ketone.
3) Using phenol and methyl vinyl ketone as raw materials
Using phenol and methyl vinyl ketone as raw materials, the raspberry ketone is synthesized by condensation reaction of phenol and methyl vinyl ketone in an acidic catalyst; Raspberry ketone was synthesized by selective addition reaction using vinyl vinyl ketone as the starting material.