Synthetic method for 2,6-dimethy-5-heptenal

Abstract

The invention discloses a synthesizing method of 2, 6-dimethyl-5-heptene aldehyde, which comprises the following steps: 1) dissolving 6-methyl-5-heptene-2-ketone and aluminium isopropoxide with molar rate at 1:0.35-1 into benzene or toluene solution; reducing under 60-120 deg.c; hydrolyzing into 6-methyl-5-heptene-2-alcohol; 2) halogenating 6-methyl-5-heptene-2-alcohol and halogenating agent with molar rate at 1:0.35-2 under -10-80 deg.c to produce 2-chlorine-6-methyl-5-heptene or 2-bromine-6-methyl-t-heptene; 3) reacting 2-chlorine-6-methyl-5-heptene or 2-bromine-6-methyl-t-heptene and magnesium to produce Grignard reagent; allocating the composition and formic ether with molar rate at 0.5-1:1 under -10-30 deg.c to do Grignard additional reaction; hydrolyzing; decompressing; distilling; obtaining the product.

Description

Technical field [0001] The invention relates to a method for synthesizing 2,6-dimethyl-5-heptenal. Background technique [0002] 2,6-Dimethyl-5-heptenal is both an organic synthesis intermediate and a perfume monomer. It is generally yellowish liquid, because of its melon aroma and melon taste, it is also called melonal (melonal). Its molecular formula is C 9 H 16 O, the relative density at 25°C is 0.85. In addition to being used in organic synthesis, it is also widely used in the food industry. The synthesis method reported in the literature is as follows: [0003] Corma et al. mentioned that the current method of industrial production of 2,6-dimethyl-5-heptenal is mainly obtained by glycidyl ester condensation of 6-methyl-5-hepten-2-one, followed by decarboxylation. This method has a total of four reactions, the reaction conditions are harsh and the by-products are many, and there are many drawbacks in practical applications. Therefore, they proposed an aldol condensation react...

AI Technical Summary

Problems solved by technology

Therefore they proposed a kind of 6-methyl-5-hepten-2-ketone and acetaldehyde to carry out aldol condensation reaction earlier to obtain 3,7-dimethyl-2,6-diene-octyl aldehyde (citral ), then H 2 o 2 As an oxidizing agent, the method (Journal of Catalysis, 234 (1), 96-100; 2005) of synthesizing 2,6-dimethyl-5-heptenal under the catalysis of tin oxide, this method technique is simpler, from citral The total yield to melon aldehyde can reach 95%, but the performance of catalyst directly affects the reaction yield, and the cost of adopted catalyst, raw material and auxiliary reagent is all higher, is not suitable for industrialization

[0004] Tietze et al. reported that 3,7-dimethyl-1,6-octadiene was used as raw material, with O 3 Selective reduction obtains the method (Angewandte Chemie, 100 (9), 1200-1; 1988) of 2,6-dimethyl-5-heptenal after oxidation again, although this method has only one-step reaction, the reagent used is various, The side reactions are complicated, the total yield is only 37%, and the subsequent separation is also relatively difficult

[0005] Takano et al. reported that 3-methyl-1-chloro-2-butene was used as a raw material to form a Grignard reagent with magnesium, and then react with 2-methyl-acrolein to generate 2,4,4-trimethyl-1 , 5-diene-3-hexanol, synthesized 2,6-dimethyl-5-heptenal (Heterocycles, 23(1), 41-4; 1985) after isomerization with KH, but the reaction required The raw material 2-methyl-acrolein is difficult to obtain

[0006] Kulkarni et al reported a synthesis of 2,6-dimethyl-5-heptanoate by decarboxylation at 280°C using 3,7-dimethyl-6-ene-2,3-epoxyoctanoic acid butyl ester as raw material The technology of alkenal (Organic Preparations and Procedures International, 10 (2), 73-7; 1978), although this method is only one-step reaction, reaction condition is harsh, and equipment requirement is high, and raw material preparation is more difficult, and its yield is also low in addition. only 75%