Method for preparing methyl heptenone by using 3-methylcrotonaldehyde

Abstract

The invention provides a method for preparing methyl heptenone by using 3-methylcrotonaldehyde, which comprises the steps of condensation and selective reduction, wherein the step of condensation comprises the sub-steps of adding acetone and a catalyst, and dropwise adding 3-methylcrotonaldehyde; and the step of selective reduction comprises the sub-steps of adding materials and carrying out hydrogenation reaction; and the sub-step of adding materials, namely adding 1 part of methyl diheptenone, 0-10 parts of a solvent, and 0.001-0.05 part of transition metal Pd / Rh catalyst precursor compounds and diphosphine ligand compounds into a reaction kettle. According to the invention, through two-step reaction, the mole yield of the methyl diheptenone to 3-methylcrotonaldehyde is high, and the methyl heptenone product content reaches 98.0-98.7%; in the step of selective reduction, the conversion rate of methyl diheptenone is greater than or equal to 99.0%, and the selectivity reaches 90.8-94%; and in the step of condensation, the conversion rate of 3-methylcrotonaldehyde is 99.0%, and the mole yield of the methyl diheptenone to 3-methylcrotonaldehyde reaches 89.8-92.7%.

Description

technical field [0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a method for preparing methyl heptenone from isopentenal. Background technique [0002] Methyl heptenone, chemical name: 6-methyl-5 hepten-2 ketone, is an important fine chemical intermediate and the main raw material for the industrial preparation of linalool, citral, ionone, the latter Vitamin A, vitamin E and various flavors and fragrances can be further prepared. [0003] The methods for synthesizing methylheptenone in the prior art mainly include acetylene-acetone method, isoprene method and isobutylene method. [0004] The acetylene acetone method was first industrialized by the Swiss F.Hoffmann-LaRoche company. This method uses acetylene and acetone as raw materials to first synthesize methyl butynol, which is then selectively reduced to enol, and then combined with ethyl acetoacetate through Caroll The reaction produces methyl heptenone. The synth...

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Problems solved by technology

[0015] (1) Low selectivity, poor atom economy, low product yield, and low conversion rate of raw materials;

[0016] (2) The existing method of synthesizing methyl heptenone by isobutylene requires high temperature and high pressure reaction, which requires high equipment;

[0017] (3) High production cost;

[0018] (4) The phase transfer catalyst used in the prior art is insoluble in the reaction system and mixed in the solid phase of the by-product after the reaction, which makes separation difficult and the use time is short;

[0019] (5) The separation, purification and raw material recovery process is complex; and the existing method for synthesizing methyl heptenone by isoprene method uses chlorine-containing compounds in the route, which causes great corrosion to equipment and environmental pollution

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