DE1493131A1 - Process for the preparation of alkylcyclohexenes - Google Patents

Description

OR. ELISABETH JUNG AND DR. VOLKER VO8SIU8

PATENTANWXlTt

• MONCHtN Il> SlIQtSSTRAM (It · TCtCPON 34 «0« 7 · TCLtQRAMU-A

P 2407 / H / O MUnchen, the 15th Dosomber 1965

SHELL IKTElUvATIOrALE USSTiARCII iSAAT "CHAFPIJ N.Y., Den HOAg / HDLLAiD

"Process for the preparation of alkylcyclohexenes"

Priority: October 17th, 1964 / USA Azunelde-Nr. 419 195

You Krfinduntf relates to a method for producing τοη Alkyloyolohgxenes by partial reduction of alkylbenzene

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MONOHfN NB ». OANMOIITO * MUTOONf OANK A.% MONCNfN. ilO ^ OLOOTN. Vt. «Tffc MO.

• AD ORIGINAL

-Z-

In the patent application S 97 558 IVb / 12 ο is a method described in the aromatic compounds by reaction in the liquid phase with alkali metals with atomic numbers from 11 to 55 and connection. gen of the formula RNH «, in which R represents a hydrogen atom or an alkyl group, in part be reduced. Ammonia is preferably used here. Benzene is used as an aromatic starting material particularly suitable, while sodium and potassium are the preferred alkali metals.

It has now been found that the partial reduction of alkyl-substituted benzenes gives better results with respect to the yield and the isomer distribution of the product can be achieved when primary amines are used as NHp-containing compounds and Potassium and / or rubidium can be used as alkali metals.

The invention accordingly relates to a process for the preparation of alkylcyclohexenes by converting alkylbenzenes into liquid phase with alkali metals with atomic numbers from 11 to 55 and compounds containing NHg groups, which is characterized by this is that the reaction is carried out with primary amines and potassium and / or rubidium as alkali metals be used.

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BATH ORIGINAL

U93131

Suitable aromatic precursors are alkylbenzenes with one or more alkyl groups including cycloalkyl groups, containing 1 to 14 carbon atoms. Preferably the compounds contain 1 to 3 alkyl groups. Suitable are e.g. toluene, ethylbenzene, cumene, tert-butylbenzene, tert-butyltoluene, p-I) ethylbenzene, ra-diioopropylbenzene, Xylene, o-di-n-propylbenaol, cyclohexylbenzene, p-cyclopontyltoluene, hexylbenzene, mesitylene, pseudocumene, 1,3,5-tripropylbenzene, n-butylbenzene, octylbenzene, m-octylethylbenzene, Decylbenzene, dodecylbenzene, "(3-methylcyclohexyl) benzene, Tetradecylbenzene, etc.

In general, alkyl substituents are opposite the analogous cycloalkyl substituents are preferred, and very special ones are conoalkylbenzenes with an acyclic Alkyl group with 1 to 4 carbon atoms suitable.

The tetralin represents the somewhat more specific pail counted as one of the dialkylbenzenes used according to the invention taking into account that in the pail of 1 »2-Dialkylbenzenes the two alkyl groups together too can form a divalent alkylene group having a total of 4 carbon atoms.

The alkali metal used for the process according to the invention Potassium and / or rubidium are used. While it is known that lithium leads to the same reduction of an aromatic

Connection leads, cind sodium and cesium for the

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BATH ORIGINAL.

U93131

not suitable for use in amine solvents, as these Metals only lead to a limited conversion of the aromatic compound. Especially from v / irtachaftlichen For reasons, potassium is preferred to rubidium.

Without wishing to be bound by any particular theory, it is believed that the alkali metal is directly reacts with the aromatic compound and thereby creates a monometal derivative, e.g. a free radical anion of Benzene, which then reacts with the solvent, whereby water "substance is introduced into the aromatic ring. Further reactions then lead to the formation of the desired cyclohexene product. So are for a complete transformation one mole of the aromatic compound requires 4 gram atoms of the alkali metal. The alkali metal is preferably used in the same amount as the aromatic compound or in excess. If none Complete conversion of the aromatic compound is required lesser amounts of the alkali metal can also be used. The ratio of gram atoms of the alkali metal to moles of the aromatic compound is averagely 2 * 1 to 10: 1 and preferably 4 * 1 to 8t1. Dft β Alkali metal comes either in pure form or in pore form a mixture of an alloy with other metals used by this group. Mixtures of KnIium are suitable and rubidium in every proportion. Quite surprisingly

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has been shown that mixtures of potassium and / or rubidium with other alkali metals, the use of which is unsuitable for Rieh alone have a more reducing effect on the aromatic compound than the potassium contained in the mixture or amount of rubidium is calculated. Though sodium Alloin in itself causes little or no conversion of the aromatic compound, a.B. a mixture from sodium and potassium a stronger conversion of the aromatic Compound than it corresponds to the potassium contained in the mixture. So can mixtures of a single suitable alkali metal such as potassium or rubidium with a single unsuitable alkali metal such as sodium or cesium, with each being appropriate and unsuitable alkali metals in each matching Ratio can be included to when using a To obtain satisfactory results for a small mixture, let θβ wish 3Word that the mixture be at least 1 gram atom Contains potassium and / or rubidium for 1 mole of the aromatic compound. In the modified invention Process using a mixture of suitable and unsuitable alkali metals is a ratio of gram atoms of total alkali metal to colon of aromatic Connection from 2x1 to 1q: 1 sufficient, provided « that «the mixture contains at least 1 gram atom of potassium and / or Contains hubidium per KoI of the aromatic compound

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U93131

The method of the invention is carried out so that the alkylbenzene with. the alkali metal in the presence oa liquid aliphatic amine is brought together. 0b ~ probably also partly aliphatic polyamines as well as primary ones Amines can be used, but the results will be great with an aliphatic primary amine, especially one lower alkylamine with 1 to 4 carbon atoms, e.g. methylamine, ethylamine, n-propylamine, n-butylamine, isopropylamine, sec.Butylamine and Isobutylamine ^ n, achieved "Am the most suitable is an n-alkylamine, in particular with 1 to 2 carbon atoms, e.g. methylamine and xthylamine · Das appears to be the amine used in the process according to the invention to meet different punctures. The amine serves as a solvent for the organic and inorganic reactants and also as a source of the hydrogen introduced into the benzene nucleus of the aromatic compound will. In the process of the invention, the partial alkali product is an amide made from potassium and methylamine forms e.g. potassium methamide. From such an alkyl anide product becomes the alkali metal by amide exchange recovered with ammonia, whereby an alkali metal arid, e.g., potassium amiA, which forms the corresponding Alkali metal hydride is hydrogenated, whereupon the elemental alkali metal is liberated by pyrolysis from dta hydride. In * the modified method according to the invention, at which the alkylamine uses as a single solution

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BATH ORIGINAL

U93131

is the i'.ol ratio of the amine to the aromatic Compound generally 7: 1 to 50: 1 and preferably 12: 1 up to 30: 1. The amine is preferably used in a form that does not contain any substances containing hydroxyl groups, e.g. water, alcohol or contains carboxylic acids, since this leads to undesirable by-products in the recovery of the alkali metal would lead. Although small amounts, i.e. up to about 5% by weight, based on the total solvent, of hydroxyl-containing Substances can be tolerated without restricting the advantages of the process according to the invention are, it is preferred to use a solvent which is free from compounds containing hydroxyl groups.

The inventive method can be in the presence of inert Diluents such as hydrocarbons, e.g. hexene, Heptene, cyclohexane, etc. You present one however, such a diluent offers no advantage that outweighs the increased difficulties in product separation »so that in the preferred embodiment of the invention no inert diluent is used.

The procedure \ ill at slightly elevated temperature. An advantage of using an amine detergent over ammonia as a single solvent is that the process requires a lower temperature. Suitable reaction temperatures

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8AD

be between 15 and 11O ⁰ C, generally temperatures between 20 and 100 ⁰ C and in particular between 30 and 80 ⁰ C are preferred. The reaction is carried out at atmospheric pressure or at a higher or lower pressure, as long as the reaction partners are in a practically liquid form. Suitable reaction pressures are 5 to 50 at, the most common are pressures between 10 and 40 at.

After the reaction has ended, the product mixture is separated and the desired cyclohexene product by the usual methods, z.d. by fractional distillation, selective extraction, crystallization, etc., ^

The product of the process according to the invention consists of an alkylcyclohexene which is formed by the uptake of 4 hydrogen atoms in the aromatic ring of the alkylbenzenes used. When toluene is reacted, for example, a mixture of 1-methylcyclohexene, 3-methylcyclohexene and 4-methylcyclohexene is obtained. A special part of the process according to the invention consists in the favorable isomer distribution which results from the reduction of the alkylbenzenes. 1-methylcyclohexene represents %. B. because of the known pyrolysability of this icomer to ethylene

and isoprene is the most desirable isomer in the Heduction of toluene. In those with lithium and one

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U93131

In the process carried out, the content of the 1-methyl isomer is in the product mixture approximately 65 5 *. The invention «- However, according to the method gives a selectivity with respect to the formation of 1-methylcyclohexene of over 90 Jt.

The cyclohexene products which can be prepared according to the invention are as chemical intermediates of importance

The inventive method is illustrated by the following examples explained in more detail.

example 1

To the difference in the isomer distribution in the case of the inventive Process au explain, experiments are carried out, the reduction of the toluene with lithium and Potassium occurs as alkali metals. In each case, the reaction partners are entered into an autoclave, which then sealed and for the specified time at the reaction temperature is held. The reactor is then cooled down, opened, and the product is made from it removed. The organic and inorganic compounds are separated by distillation and the amount of product is determined duroh oasis chromatography. The results of this Experiments are compiled in Table I, the selectivity being based on the percentage content found in the product mixture refers to 1-methylcyclohexene.

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U93131

- ίο -

Table I.

toluene
Mole metal
g-atony Methylamine
Mole Temp.
⁰ C Time
Hours. conversion
of toluene Selecti
vity 0.102 11, 0.4 1.9 60 3 43.1 66.3 0.1 K, 0.4 1.9 60 0.83 48.5 83.7 0.1 K, 0.4 1.9 60-74 0.5 47.1 90

Example 2

Using the same procedure as in Example 1, experiments are carried out under Use of 0.1 moles of various alkylbenzenes, 0.4 moles Alkali metal and 2.0 moles of methylamine carried out as solvents. Bio results are given in Table II, with the selectivity is based on the percentage of 1-alkylcyclohexene found in the product mixture

Table II

Alkylbenzene metal Temp.
⁰ C Time
3td. conversion
of the alkyl
benzene selectivity Curaol
t-butylbenaol
t-butylbeneol K
X
Li 63-67
60
60 3
2
8th 62
75.5
59.8 83.4
86.1
69.6

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Example 3

Carry the same procedure as in Example 1 Vereuoh · leads are using 0.1 mole of various di- and Trialkylbemsole, 0.4 moles of potassium, and 2,0 moles of methylamine carried *. The results are given in Table III, where. the selectivity is based on the prosentic content found in the product mixture for the named product

Table III

Alkylbeneol Temp. Time
Hours. Conversion of the
Alkylbeneols selectivity
product o-xylene
Mesitylene
Tetralin 60-68
50-69
60-70 1.25
2
2.3 33.6
50.4
40.3 83 »1,2-dimethyl
oyclohexene
100, 1,3,5-trietnyl
cyclohexene
95, 9,10-octalin

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Claims (8)

U93131 Claims 1 · Process for the preparation of alkylcyclohoxenes by reaction of alkylbenzenes «, in the liquid phase with alkali metals with atomic numbers from 11 to 55 and compounds containing NHp groups, characterized in that the implementation with primary Amines is carried out and potassium and / or rubidium are used as alkali metals. 2. The method according to claim 1, characterized in that the Ratio of grammatoraen of alkali metal to moles of aromatic Connection in the conversion is 2: 1 to 10: 1. 3. The method according to claim 2, characterized in that said ratio is 4t1 to 8x1. 4 «A method according to claim 1-3» daduroh in that w are / is used as a primary amino methylamine and / or methylamine " 5. Process according to claims 1-4, characterized in that the molar ratio of primary amine to aromatic compound is 12: 1 to 30ti. 6. The method according to claim 1-5, characterized gekennceichnet that the reaction is carried out in the absence or virtually in the absence of compounds containing hydroxyl groups / ird _ö 909806/10 70 H93131 7. The method according to claim 1-6, characterized in »that the reaction takes place at a temperature between 30 and 80 C. is carried out. 8. The method according to claim 1-7 »characterized in that dafl the alkali metals are regenerated from the corresponding alkylamides formed in the reaction. 909806/1070