DE2257709A1 - PROCESS FOR COUPLING AROMATIC COMPOUNDS - Google Patents

Description

DR. BERG DIPL.-IMG. STAPF

PATENT LAWYERS 8 MUNICH 8O. MAUERKIRCHERSTR. 48

Lawyer File 23 116

Monsanto Company St. Louis, Missouri / USA

Process for coupling aromatic compounds

The invention relates to the use of molecular Oxygen for coupling aromatic compounds, including substituted aromatic compounds

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such as phenols or alkylbenzenes, ■ with the formation of polyaromatic Compounds such as phenylphenol, dimethylbiphenyl, Dicarboxylic acid biphenyl and others.

Have coupled aromatic compounds and especially substituted coupled aromatic compounds proved to be useful and environmentally friendly functional fluids. Disubstituted polyaromatic Compounds are also useful as intermediates in the manufacture of polymers. The polymers obtained from such monomers have both aromatic Ske, as well as the properties normally common with such polymers, such as high temperature resistance and low flammability.

Until now, it was customary to couple to form benzene-diphenyl by passing benzene through a 6 & O 85O ⁰ C heated hot tube. This reaction is not suitable for obtaining substituted diphenyls from substituted benzenes. Such strict conditions usually attack the substituent and lead to an undesirable loss of reaction participants and reaction product. One method that is frequently used when substituted biphenyls are desired is the halogenation of the substituted benzene and aii-

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closing .Implementation of this connection with increased Temperature of about 300 ° C in the presence of copper powder. However, the process is poor in yield and, due to the large amount, is in halide converted copper powder is also expensive. Furthermore is this process is not generally applicable to substituted aromatic compounds because of the strict reaction conditions exclude the use of many substituted aromatic compounds.

It was also known that certain metal compounds act as oxidizing agents and used to couple aromatic compounds under gentler conditions can be. In a high oxidation state, these metals can be reduced to obtain diaromatic compounds can be used. It was known that diphenyl mercury biphenyl and metallic mercury and palladium acetate are diaromatic compounds and metallic palladium results. Because in these reactions expensive metal salts are used in stoichiometric amounts they are of little practical value. So far it has not been possible to find cheap oxidizing agents like that e.g., molecular oxygen, to carry out this coupling reaction.

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Previously known attempts, the expensive oxidizing agent Reoxidizing using standard procedures only resulted. to procedures that are either disproportionately expensive or their severe conditions gave only low yields.

A process for converting unsubstituted as well as substituted benzenes, in particular; of alkylbenzenes and hydroxybenzenes into the corresponding diphenyls, Phenyl ethers and the like, with good yield, under relatively gentle reaction conditions and when using cheap molecular oxygen

I '

as an oxidizing agent, would represent a significant port step. This is essentially what the present invention is concerned with.

The invention relates to a method for coupling aromatic compounds Compounds of the formula

in which η is an integer from 0 to 5 and each of the R groups is a hydroxy *, alkoxy, alkyl, acyl, alkanoate, aryloxy, aryl, alkaryl, Aralkyl, hydroxylated monovalent hydrocarbon, halogen, nitro, cyano,

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■ ~ 5 -

Amino, carboxyl., Carboxylic acid ester or sulfate group and any two at adjacent Carbon atoms of the benzene ring located R groups with the formation of a carbo, cyclic or heterocyclic ring can be connected,

with the help of molecular oxygen to produce coupled aromatic compounds. The. Coupling of these aromatic compounds by molecular oxygen in the presence of a mercury compound and a Group VIII metal or metal compound. This procedure is special Value in the production of compounds such as phenylphenol, diphenyl, diphenyl ether, dimethyldiphenyl, dicarboxylic acid diphenyl, Dimethoxydiphenyl, bis-phenoxydiphenyl, Dibenzofuran and other related compounds used as heat exchange fluids and functional fluids as commercial products are of interest.

Compounds of the formula above that are useful as reactants in the process of the invention include a variety of aromatic compounds. If the integer η = 0, then the compound is benzene. By doing . The extent to which η increases is the number of substituted Benzene in the context of the 'formula bigger and bigger. The MA-

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ximal value of η 1st 5, since the last carbon atom of the benzene ring must remain free so that the catalyzed coupling reaction according to the invention can take place. Preferred values for η are 0 to 2.

R groups in the formula can be all groups »the do not interfere with the coupling of the aromatic ring under the reaction conditions. Suitable R groups are for example hydroxy, alkoxy, aryloxy, alkyl, aryl, alkaryl, aralkyl, acyl, alkanoate, hydroxylated monovalent Hydrocarbon, halogen, nitro, cyano, amino, carboxyl, carboxylic acid ester or sulfate groups. The hydrocarbon substituent can be any size having from 1 to 20 or more carbon atoms.

For practical reasons, a hydrocarbon substituent is used seldom have more than 12 carbon atoms and generally no more than 6 carbon atoms. Hydroxy groups, either individually or in conjunction with other hydroxy groups, or other groups different therefrom, are preferred. Furthermore, there are alkoxy groups preferred. Alkyl groups, carboxylic acids and esters are particularly preferred groups. Suitable R groups are for example methoxy, ethoxy, decyloxy, phenoxy, tolyloxy, xylyloxy, methyl, ethyl, cyclohexyl, Dodecyl, phenyl, diphenyl, tolyl, xylyl, benzyl,

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Phenylethyl, 2-ethylphenyl, formyl, acetyl, acetate, Propionate, fluorine, chlorine, bromine and iodine, nitro, carboxyl and alkyl carboxylate groups.

If one or more R groups are phenyl or phenoxy groups, then the reactant suitable for the process according to the invention can with some of the means of the reaction end products obtained be the same or very similar to them. In other words, some of the reaction products can be reacted further to form other polyaromatic compounds with more than two aromatic compounds Wrestling. Diphenyl, Terphenyl, Diphenylather and Phenylphenol are such reaction lines.

The substituents on any two adjacent carbon atoms of the aromatic ring can also form a carbocyclic or heterocyclic ring be connected, creating a condensed ring structure. Typical condensed ring compounds include naphthalene, benzofuran, indene, and chlorobenzofuran. Suitable reactants include benzene, toluene, xylene, Ethylbenzene, substituted naphthalenes, phenol, anisole, ethoxybenzene, phenyl acetate, phenylhexanoate, phenoxybenzene, Tolyl acetate, 4-chlorophenyl acetate, 2-chloro xylene, bromobenzene, Nitrobenzene, nitrotoluene, trichlorobenzene, 4-chlorophenol, 4-methylphenol, phenylbenzoate and others

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The reaction according to the invention can be carried out with pure reactants or solutions or dispersions of the reactants. Many of the reactants, such as benzene, toluene, xylene, ethylbenzene, phenol, among others are
liquid under the reaction conditions used, while some highly substituted compounds and condensed ring compounds can be solid and are advantageously reacted in a solution. All solvents that do not interfere with the reaction or react with the product or the reactants can be used
be used. Suitable solvents are, for example, alcohols such as methanol, ethanol and propanol, carboxylic acids such as acetic acid and benzoic acid, and water
aromatic and aliphatic hydrocarbons such as benzene, cyclohexane and isooctane. Preferred solvents
are alcohols and carboxylic acids.

The catalyst system used constitutes that part of the invention which enables the aromatic compounds under the relatively gentle reaction conditions, as provided here, to polyaromatic Convert connections. In the broadest sense, the catalyst system consists of a mercury compound together with a Group VIII metal compound.

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The mercury compound can be any compound which can be dissolved in a solvent suitable for the process according to the invention. To the appropriate Compounds include mercury halides, such as the chloride and bromide, and other salts such as the sulfate, sulfite, Nitrate, phosphate, borate, carbonate, fluorate, acetate and propionate. Those mercury salts are preferred which contain an oxyanion, such as nitrate, sulfate and carboxylate. .

The mercury compound is combined with a metal or a metal compound of Group VIII of the Periodic Table is used. Group VIII metals are iron, Cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum. The preferred metals of these Group are nickel, palladium and platinum. Particularly preferred becomes palladium. The metal can be added initially as free metal. Optionally, the metal can also be added as a salt or chelate. In the remainder of the description, the term "metal compound of Group VIII "is used for both the free metal and the salts and chelates of the metal. 'The'metal salts may contain all anions as already mentioned as being suitable for the mercury compounds are. As in the case of the mercury compounds, too.

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Group VIII metal compounds that are an oxyanion included, preferred. Suitable compounds include nickel iodide, palladium bromide, platinum chloride, Nickel nitrate, palladium sulfate, platinum acetate, nickel formate, Palladium propionate, platinum acetylacetonate and complexes of the metal ions with chelating agents such as citric acid , Ethylenediaminetetraacetic acid and others. Except for the metal carboxylates such as palladium and platinum acetates and benzoates, the metal halogen-substituted carboxylates form a further preferred series of metal compounds Group VIII. These include bis (trifluoroacetate) palladium, bis (chloroformate) platinum and bis (chloroacetate) Iridium.

A third component can optionally be included in this two-component catalyst system. The third Component is a compound that functions as a redox agent under the reaction conditions used. A Redox agent is a compound that oxidizes in a reaction medium from one substance and from another can be reduced, or vice versa, making them again maintains its original oxidation state. Particularly preferred redox agents are those with molecular Oxygen can easily be reoxidized to its original state. In general, any multivalued Metal salt whose oxidation potential is more positive

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is as that of ^{Group 1} metal ¥ 111, as. Redox agents can be used in the method according to the invention. Furthermore, the polyvalent metal ion should preferably be present in the salt in a valence state which is higher than its lowest ionic valency state. The anions of these salts can be the same or similar to those present in the mercury compounds and platinum metal compounds, i.e. halides, nitrates, sulfates, carbonates, acetates, etc. The polyvalent metal with the required oxidation potential can be copper, iron, manganese, cobalt, nickel, cerium , Uranium, chromium, molybdenum, vanadium, etc. Of the polyvalent metal salts, the copper (II) and iron (III) salts are preferred. Suitable redox compounds include copper (II) chloride, copper (II) acetate, iron (III) bromide, iron (III) acetate, manganese nitrate, cobalt sulfate, nickel formate, cerium acetate, uranium carbonate, chromium nitrate, molybdenum nitrate and vanadium propionate. ·

The presence of some anions, such as halide anions, can significantly affect the reaction of some of the aromatic reactants. For example reduce halide ions, which are considered to be the reaction system Mercury chloride or palladium bromide are added, essentially the yield of obtained from alkylbenzenes

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polyaromatic compounds. The manufacture of polyphenyl ethers and other similar compounds however, phenols and similar oxidized benzenes remain essentially unaffected by the presence of halide anions in the reaction medium. From this it can be understood that the result will vary considerably can., depending on the use of special catalytic compounds with special reactants.

In the most preferred embodiment of the invention the aromatic coupling reaction in the presence of the three metallic components of the catalyst system carried out, namely the mercury compound, the metal or the metal compound of Group VIII, and the polyvalent metal redox compound, also in the presence of a molecular oxygen containing gas. In this embodiment is the reaction is catalytic with respect to all three metallic compounds. Another way of presenting this embodiment is to use the oxidative Coupling of Aromatic Compounds In accordance with the following exemplary reaction understands:

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(Ο

+1/2 O.

HgX PtX ν,

2 (optional)

In this representation, the oxygen is not part of the catalyst, but one of the Reagent whose reaction with aromatic compounds is catalyzed by the two- or three-component catalyst system.

The components of the catalyst system can be present in very different amounts. The Group VIII metal component can be present in a molar concentration of from about 0.001 or less to 5 or more, preferably in from about 0.005 to about 1 molar concentration. Practical considerations on how to obtain a useful reaction rate and how to keep the "consumption of excess, expensive metal low, show that a 0.005 to 0.05 molar range is particularly useful. "'

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The amount of the mercury compound used is relative to the amount of the Group VIII metal compound expressed. The molar ratio of the mercury compound to the Group VIII metal compound is about 1:10 to about 10: 1, preferably from about 1: 2 to about 2: 1, and about equimolar amounts are even more favorable.

The amount of redox agent used can also be expressed relative to the Group VIII metal compound will. The molar ratio of redox compound to Group VIII metal compound can be between 0: 1 and about 50J1, preferably between about 0: 1 and about 2: 1.

The reaction can be carried out at any temperature, the maximum temperature limit being determined by the heat resistance of the reactants. The preferred reaction temperatures are between 0 and 300 ^° C., most preferably between about 40 and 200 ^° C. The reaction pressure is also not critical. In general, the reaction can take place at any pressure between less than 1 and several hundred atmospheres. The preferred pressure will depend on how large the reaction vessel is and how much space is available for the molecular oxygen. For example, it turned out

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in a 1 liter reaction vessel where half the volume was available for the oxygen Oxygen or air pressure of 5 to 100 atmospheres as cheap.

In the catalytic process, the reactants in a reaction vessel into which a solution or dispersion of the catalyst mixture is also added will. The mixture is brought to the desired temperature and pressure, so that the coupled products are obtained. After the reaction has ended, the products can be replaced by conventional Processes such as crystallization and distillation can be separated.

In an alternative implementation, the above reaction described heterogeneously over a bed of supported Catalyst carried out. The metal components can be attached to any suitable using standard known methods inert carrier are bound. The catalyst concentration on the support is not critical and can be largely different. The most favorable ratio is determined by the specific reaction conditions used determined, i.e. flow rate of the reactants, temperature, size of the catalyst bed, desired Productivity, etc. The reactions participants

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can be vaporized and the gas mixture passed over the catalyst in a heated chamber. The temperature should be high enough to keep a favorable amount of reactants and products in the vapor phase but not so high that reactants or products are decomposed. Usually the Temperatures between 50 and 350 C. The pressure can be between sub-atmospheric values and 100 atmospheres and more lying. The reactants can be added with or without a diluent gas. Oxygen can do that Reaction medium can be fed continuously or by one or more injections.

The products obtained from this reaction can be very different in their structure. This way two types of coupling are possible. In one type of coupling reaction, core-to-core coupling occurs under Formation of diaromatic compounds directly linked by carbon atoms of the respective aromatic rings are connected. In this case the products have the general formula

(n)

The information in the above description applies to R and η of the aromatic compounds that can be coupled.

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A second type of coupling occurs when there is a coupling between the side chain and the core. If one of the substituents R ^{1 has} a replaceable hydrogen atom, this can be removed during the reaction in order to couple ^{the aromatic rings via a bridging R 1 group.} Compounds of this type have the general formula

where R and η have the meaning given above and R ^! -CH ₂ -, -CH ₂ - ,, -CH ₂ -, -CH = CH-, -CH ₂ CH ₂ CH ₂ -, CH ₃ -C-CH ₃ , -0-, -S-, -NH- , SO ₂ -, oa is.

The aromatic group need not be limited to benzene either stay. Condensed ring structures such as naphthalene, Anthracene and the like are produced with this method coupled as well as heterocyclic aromatic compounds, such as pyridine, thiofuran, furan, etc.

Note that a single reactant reacts with itself to form symmetrical dimers can be coupled, or that a mixture of reactants can be used for cross coupling, to obtain unsymmetrical dimers. The coupled products can also be further converted into trimers, tetramerers and

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even higher polymers can be implemented.

example 1

80 ml of acetic acid, 20 ml of benzene, 20 g of phenol, 0.2 g of mercury acetate and 0.8 g of copper (II) acetate are placed in a 200 ml autoclave lined with titanium mixed. The autoclave is closed with pure oxygen to a pressure of 8.6 kg / cm and to a Brought temperature of 80 ° C. A solution of 0.2 g of palladium chloride (PdClp) in acetic acid is poured into the reaction vessel given and the reaction continued for 4 hours. The reaction mixture is then cooled and filtered off. Diphenyl, 2-phenylphenol, ^ -phenylphenol, Dibenzofuran and Diphenylather are means Gas chromatography detected.

Example 2

The procedure of Example 1 is exactly repeated, except that 0.4 g of bis (trifluoroacetate) palladium, Pd (OOCF.,) _{2 is used instead of PdCl 2} . Gas chromatography shows the presence of diphenyl, 2-phenylphenol, 4-phenylphenol, dibenzofuran and diphenyl ether.

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Example 3 -

A mixture of 50 ml of benzene, 50 ml of acetic acid _3, 20 g of phenol, 0.2 g of mercury acetate, 0.2 g of palladium acetate and 10 g of copper (II) acetate is heated for 8 hours at at-

t '■' ■

atmospheric pressure and continuous flow of oxygen held at reflux. Gas chromatography shows the presence of diphenyl, 2-phenylphenol, 4-phenylphenol, Dibenzofuran and diphenyl ethers.

Example 4

A mixture of 50 g of 2-methylphenol, 50 g of naphthalene, 50 g toluene, 50 ml acetic acid, 0.3 g mercury acetate, 0.3 g of platinum acetate and 12 g of iron (III) chloride is 8 Heated to reflux temperature for hours. While this time, air is carried through the boiling liquid blown at a rate of about 100 ml / min. To Cooling, the reaction mixture is filtered and the Solids washed out with 300 ml of benzene ■ The filtrate contains l- (2-Methyi-4_hydroxyphenyl) naphthalene, 4-tolylphenol, 4- (4-methylphenyl) toluene, 4- (3-methyl-4-hydroxyphenyl) toluene and other polyphenylene compounds.

Example 5 "\

In a 300 ml autoclave, with stirring

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100 ml of toluene, 0.5 g of palladium acetate and 20 g of mercury acetate are added. The autoclave is closed with

2 brought oxygen under a pressure of 22.13 kg / cm and ^{heated to 150 0} C for several hours. After cooling and releasing the gas, the liquid fraction is analyzed by means of gas-liquid chromatography: it contains a mixture of 2, 3 ^f , 2.4 ·, 3.3 ', 3.4' and 4.4 · dimethyldiphenyl. The selectivity based on benzene consumed is 90 % and the conversion is 30 %.

Example 6

A catalyst composed of 2 % palladium acetate and 5 % mercury acetate on silica is placed in a heated reaction vessel, the temperature of which is kept at 150.degree. Toluene and acetic acid are vaporized with a gas stream containing molecular oxygen and the stream is passed over the catalyst layer. The liquid condensate collected after the reaction shows on gas-liquid chromatography that it contains both a mixture of dimethylbiphenylene and benzyl acetate.

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Example 7

A reaction as in Example 5 is carried out, however the toluene is replaced by anisole. Gas-liquid chromatography the solution obtained shows the presence of at least 3 isomers of dimethoxydiphenyl. * ·

Example 8

A reaction as in Example 5 is carried out, however the toluene is replaced by methyl benzoate. Dicarboxylic acid and biphenyldimethyl ester are the main product. . . "■

Example 9 .

A reaction as in Example 5 is carried out, however the toluene is replaced by ethylbenzene '. Diethylbiphenyl is obtained, along with Äzetophenoh, phenylacetaldehyde and a small amount of phenethylethylbenzene. ■: - ■ -

Example 10 ,

A reaction as in Example 5 is carried out, however the toluene is replaced by xylene. A mixture

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from tetramethyldiphenylene and methylphenyl-dimethylphenylmethanes is received.

Example 11

A reaction is carried out as in Example 1, except that the toluene is replaced by naphthalene. A mixture from binaphthalene and ternaphthalene is obtained

Example 12

A reaction as in Example 1 is carried out, but the toluene is replaced by phenyl ether. One the product is determined to be diphenoxybiphenyl.

Example Ij

ßiphenyl is coupled as in Example 1 and gives a high yield of tetraphenyl. ,

Example 14

Following the procedure described in Example 1, chlorobenzene is used to form a mixture of dicnlor biphenyl isomers coupled.

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Example 15 '

Following the procedure described in Example 1 viir "d Mitrobenzene coupled to form dinitrobiphenyl. ■

Claims - - 2k -

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Claims (3)

Claims /. Process for coupling aromatic compounds of the formula in which η is an integer from 0 to 5 and each of the R groups is a hydroxy, Is alkoxy, alkyl, aryloxy, aryl, acyl, alkanoate, halogen or nitro group and where any two R groups attached to adjacent carbon atoms of the benzene ring can be connected to form a carbocyclic or heterocyclic ring by means of molecular oxygen to obtain coupled aromatic compounds, characterized in that the coupling of these aromatic Compounds by molecular oxygen in the presence of a mercury compound and a Metal or a metal compound of group VIII, and, optionally, a redox agent takes place. 2. The method according to claim 1, characterized in that that at least part of the said 309822/1231 - 25 - aromatic compounds phenol, benzene, toluene '"! ^: VIII or diphenyl ethers, and the metal; der-, j & rju ^, pe VI a metal compound of palladium. or "platinum, and the mercury compound is a mercury carboxylate. 3. The method according to claim 1, d a d u r c h ■ g ekmarks, that the said redox compound is an iron (III) or copper (II) salt. ^. Method according to claim 3> da. characterized in that the catalyst system contains a mercury acetate, palladium acetate and copper (II) acetate, and that the reaction is carried out homogeneously in the positive phase or heterogeneously in the gas phase. . · 309 8 2 2/123 1