DE1275050B - Process for the production of olefinically unsaturated aldehydes and ketones - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

German class:

C07c

C07d

12 ο -19/03

12fl-24

Number: 1 275 050

File number: P 12 75 050.4-42 (B 91482)

Filing date: March 6, 1967

Opening day: August 14, 1968

It is from Houben-Weyl, »Methods of Organic Chemistry ", Vol. 7/1, p. 249 ff., known, Dihydro-4H-pyrane at elevated temperature in one To split up "declining diene synthesis" into acrolein and ethylene or their corresponding derivatives; leads to unsaturated carbonyl compounds with the same carbon number as that of the starting pyran you do not. Dihydro-4H-pyrans can also be converted into derivatives of <5-oxyvaleraldehyde in the presence of acids are cleaved, but in this way unsaturated, hydroxy- and alkoxy-free Carbonyl compounds are not produced. In the Journal of the American Chemical Society, vol. 78, P. 992, and Vol. 80, pp. 5266 to 5270, it is also described that unsaturated carbonyl compounds cyclize in the presence of acids diluted with water, e.g. B. «-Methylheptenone to ice and trans- !, S-dimethylcyclohexane-ljS-diol and / 3-methylheptenone to 1,3-dimethylcyclohexadiene- (1,3) and 1-methylene-3-methylcyclohexene (2).

It is known from above-mentioned journal, Vol. 78, p 2641 known that 2,2-dimethyl-dihydropyran even at 27O ⁰ C for 2 hours in benzene shows no ring cleavage and low under the same conditions in the presence of water in addition to The amount of carbocyclic compounds mainly excretes resin-like residues.

It has now been found that olefinically unsaturated aldehydes and ketones are advantageously obtained by ring cleavage of 5,6-dihydro-4H-pyrans in the presence of water at elevated temperature and pressure, optionally in the presence of an organic solvent which is inert under the reaction conditions if the ring cleavage is carried out with 0.01 to 10 percent by weight of water at a temperature between 280 and 350 ^° C., preferably between 290 and 300 ^° C., and at a pressure between 10 and 300 at, preferably between 25 and 100 at. It is advantageous to use 0.1 to 3 percent by weight of water, based on 5,6-dihydro-4H-pyran.

According to the method of the invention, compared to the known method in γ, δ or δ, ε position to the carbonyl group, olefinically unsaturated, hydroxy and alkoxy-free aldehydes or ketones with the same number of carbon atoms as that of the starting pyran can be used in one stage and in good yield without substantial formation of carbocyclic compounds or residues are produced.

The 5,6-dihydro-4H-pyrans used as starting materials are usually made olefinic by reaction of a corresponding unsaturated aldehyde or ketone with a process for the production of
unsaturated aldehydes and ketones

Applicant:

Aniline & Soda Factory in Baden

Aktiengesellschaft, 6700 Ludwigshafen

Named as inventor:

Dr. Herbert Müller, 6710 Frankenthal;

Dr. Harald Kohl,

Dr. Horst Pommer, 6700 Ludwigshafen

a corresponding alkene prepared; however, they can also be carried out using other methods (see Houben - Weyl, Vol. 6/4 and 7/1). You can have substituents on the ring, which are preferred are aliphatic, e.g. B. carry alkyl radicals with up to 10 carbon atoms.

The reaction is carried out in the presence of preferably 0.1 to 3 percent by weight of water, based on to 5,6-dihydro-4H-pyran. The greater the amount of water used, the faster the reaction rate and the more the yields of the unsaturated carbonyl compound deteriorate by the formation of by-products resulting from hydrolysis. Instead of water can also dehydrate substances such. B. tertiary alcohols can be used. One can also do that Dihydropyran itself attach water and subject the resulting hydrolyzed compound to the reaction.

The reaction is carried at at a temperature of 280-350 ° C, preferably 290-300 ⁰ C and at a pressure between 10 and 300, preferably at between 25 and 100 is performed. The reaction pressure generally corresponds to the total vapor pressure of the components; but you can also use inert gases under the reaction conditions, ζ. Β. Also use nitrogen. If appropriate, organic solvents which are inert under the reaction conditions, e.g. B. aromatic compounds such as benzene can be added.

The reaction can be carried out as follows: In a heated to the reaction temperature The 5,6-dihydro-4H-pyran and small amounts of water and optionally a pressure reactor are used Entered solvent. Man conduct the reaction

809 590/468

within 5 minutes to 4 hours under the conditions mentioned, the mixture cools and separates the end products therefrom according to the usual methods, e.g. B. fractional distillation, from. The reaction can be carried out continuously or batchwise.

Those made by the process of the invention Unsaturated carbonyl compounds are valuable intermediates for the production of fragrances.

The parts given in the following examples are parts by weight.

example 1

300 parts of 2,6,6-trimethyl-5,6-dihydro-4H-pyran and 5 parts of water are pressed into a high-pressure autoclave preheated to 290.degree. The mixture is kept ^{at 290 °} C. with an autogenous pressure of 90 at 25 minutes. The mixture is then passed into a high-pressure separator, where it is cooled and then subjected to fractional distillation. In addition to 16 parts of unreacted 2,6,6-trimethyl-5,6-dihydro-4H-pyran with a _{boiling point of 76O} = 130 to 131 ° C, 256 parts of a mixture of cc- and /? - methylheptenone with a _{boiling point of 76O} = 170 ° C (corresponds to 90% of theory, based on converted starting pyran).

Example 2

150 parts of 2,6,6-trimethyl-5,6-dihydro-4H-pyran, 4 parts of water and 200 parts of benzene are in a pressed to 300 ° C preheated autoclave. The reaction mixture is 45 minutes at 300 ° C and 80 at left, then separated using a high pressure separator and worked up by fractional distillation. This gives 11 parts of unreacted dihydropyran, 127 parts (corresponding to 92.7% of the Theory, based on converted starting pyran) of a mixture of «- and / 3-methylheptenone and Parts residue.

Example 3

100 parts of 6-methyl-6-neopentyl-5,6-dihydro-4H-pyran parts of water and 300 parts of benzene are pressed into a pre-heated to 300 ⁰ C autoclave. The mixture is then left at this temperature and at 100 atm for one hour. The mixture is separated off and worked up in the manner described in Example 2. 16 parts of unconverted 6-methyl-6-neopentyl-5,6-dihydro-4H-pyran with a _{boiling point of 50} = 106 to 109 ° C., 70 parts (87.5% of theory, based on converted starting pyran) are obtained mixture of 5-methyl-7-dimethyl-4,5-dehydro-caprylic and its 5,6-Dehydroisomere from Kp. _a = 52 to 54 ° C and 10 parts of a residue.

Claims (2)

Patent claims: 1. Process for the preparation of olefinically unsaturated aldehydes and ketones by ring cleavage of 5,6-dihydro-4H-pyrans in the presence of water at elevated temperature and at elevated pressure, optionally in the presence of an inert under the reaction conditions, organic solvent, characterized in that the ring cleavage with 0.01 to 10 percent by weight of water at a Temperature between 280 and 350 ° C, preferably between 290 and 300 ° C, and at a pressure between 10 and 300 atm, preferably between 25 and 100 atm. 2. The method according to claim 1, characterized in that the ring cleavage with 0.1 to 3 percent by weight of water, based on 5,6-dihydro-4H-pyran, carried out. 809 590/468 8.68 © Bundesdruckerei Berlin