JPS6116371B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing unsaturated dimers of styrenes by dimerizing or codimerizing styrenes. It is known that when styrenes are dimerized or co-dimerized, saturated dimers and unsaturated dimers are generally produced. For example, in the dimerization of styrene, 1-phenyl-
3-methylindane is an unsaturated dimer with 1,
3-diphenyl-1-butene is obtained in each case. Unsaturated dimers of styrenes are useful compounds in themselves and as raw materials for various reactions, but it has not been possible to obtain unsaturated dimers with good selectivity during dimerization of styrenes. When sulfuric acid is used as a catalyst, the production of saturated dimers, trimers, and higher oligomers is unavoidable. In addition, in order to improve the selectivity of unsaturated dimers, it is necessary to lower the sulfuric acid concentration or raise the temperature, which tends to cause corrosion of the equipment. When solid acids or acid clay are used, saturated dimers are mainly produced. The present invention solves these drawbacks and provides a method for obtaining unsaturated dimers of styrenes with good selectivity and high yield through dimerization or co-dimerization of styrenes. The present invention provides that in the presence of sulfonate anions, 0
This is a method for producing an unsaturated dimer of styrenes, which is characterized by dimerizing styrenes represented by the following formula () in a temperature range exceeding 150°C. (In the formula, R is hydrogen or a lower alkyl group having 1 to 3 carbon atoms, n is the number of alkyl groups when R is an alkyl group and is 1 or 2, and when n is 2, R is the same or different alkyl group. ) The styrene used in the present invention has the formula ()
Any compound represented by the above formula may be used, but styrene, m- or p-vinyltoluene, etc. can be advantageously used, especially industrially. In the present invention, two or more types of styrenes can also be used for co-dimerization. The present invention involves dimerizing styrenes represented by the formula () in the presence of a sulfonate anion. The sulfonate anion in the present invention is represented by the formula (). R′SO ₃ ^- ………() R′ is a fluorine atom or a chlorine atom, and is further a fluorine substituted product of an aliphatic hydrocarbon residue, an alicyclic hydrocarbon residue, or an aromatic hydrocarbon residue. , a chlorine-substituted product or a bromine-substituted product. The aliphatic hydrocarbon residue preferably has 1 to 3 carbon atoms, the alicyclic hydrocarbon residue preferably has 5 to 8 carbon atoms, and the aromatic hydrocarbon residue preferably has a monocyclic or bicyclic ring with 6 to 18 carbon atoms. Typical specific examples of sulfonate anions are as follows. Fluorosulfate ion when R′ is a fluorine atom. Chlorosulfate ion when R′ is a chlorine atom. When R′ is a substituent, trifluoromethanesulfonate anion, perfluoroethanesulfonate anion, perfluoropropanesulfonate anion, parafluorobenzenesulfonate anion, 2,4,6-trifluorobenzenesulfonate anion, parachlorobenzene Sulfonate anion, 2,4,6-trichlorobenzenesulfonate anion, parabromobenzenesulfonate anion, 2,4,6-tribromobenzenesulfonate anion. In the dimerization reaction of styrene compounds, in order to allow these sulfonate anions to be present in the reaction system and proceed with the reaction, compounds in the form of acids (R′SO ₃ H) or alkyl derivatives thereof having 1 to 3 carbon atoms are used. Ester (R′SO ₃ R″) with group (R″),
A compound in the form of a metal salt represented by R′SO ₃ M or an acid anhydride represented by (R′SO ₂ ) ₂ O is added to the reaction system. Typical examples of acids that generate sulfonate anions (R'SO ₃ ^- ) are fluorosulfuric acid, chlorosulfuric acid, trifluoromethanesulfonic acid, perfluoroethanesulfonic acid, perfluoropropanesulfonic acid, and parafluorobenzene. sulfonic acid, 2,
These include 4,6-trifluorobenzenesulfonic acid, parachlorobenzenesulfonic acid, 2,4,6-trichlorobenzenesulfonic acid, parabromobenzenesulfonic acid, 2,4,6-tribromobenzenesulfonic acid, and the like. Esters are alkyl esters of these acids, and typical examples include methyl ester, ethyl ester, and propyl ester. Typical metal salts of these acids are salts in which the metal (M) is sodium, potassium, magnesium, calcium, barium, or the like. Typical acid anhydrides of these acids include pyrochlorosulfuric acid.
Of course, the acid derivatives such as esters, metal salts, and anhydrides are not limited to the above-mentioned specific examples. In order to advance the dimerization reaction of styrenes, an acid or a derivative thereof is added to the reaction system as a compound that produces the above-mentioned sulfonate anion. When these compounds are added to the reaction system, a dimerization reaction of styrenes occurs selectively in the presence of sulfonate anions generated by dissociation of the compounds. If the activity alone is insufficient for the dimerization reaction (as is the case, for example, with the above derivatives), protonic acids such as sulfuric acid or HF or
When used in combination with an acid such as a Lewis acid such as BF ₃ , FeCl ₃ , I ₂ etc., the compound is activated by acid metathesis and a sufficient amount of sulfonate anion is produced for the reaction to proceed, resulting in the formation of sulfonate anion. It is easily achieved that the dimerization reaction of styrenes in the presence proceeds to a satisfactory degree. 100% as the sulfonate anion source of the present invention
Super strong acids, which are defined as acids stronger than sulfuric acid, are most preferred because they have high activity and require a small amount of catalyst. Furthermore, even in the case of esters, metal salts, or acid anhydrides of super strong acids, equivalent effects can be obtained by combining them with protonic acids or Lewis acids. Typical superacids that generate sulfonate anions are:
Fluorosulfuric acid, chlorosulfuric acid, trifluoromethanesulfonic acid, perfluoroethanesulfonic acid, perfluoropropanesulfonic acid, etc. where R′ of R′SO ₃ H is fluorine, chlorine or perfluoroalkyl, or R′ is Halogen-substituted aromatic hydrocarbons parafluorobenzenesulfonic acid, parachlorobenzenesulfonic acid, parabromobenzenesulfonic acid, 2,4,6-trichlorobenzenesulfonic acid, 2,4,6-trifluorobenzenesulfonic acid, 2 , 4,6-tribromobenzenesulfonic acid and the like. Cationic polymerization of styrenes starts when a catalyst compound acts on a styrene monomer to generate a counter ion between the monomer cation and an anion generated from the catalyst. Further monomer is added to this counterion, and the polymerization reaction proceeds.
On the other hand, the termination reaction of polymerization is caused by a proton elimination reaction between the generated polymer ion pairs. In this case, depending on the type of anion, there are differences in monomer addition reactivity, proton elimination reactivity, and reactivity in which the anion itself is added to the polymer terminal and stabilized. For example, in the case of sulfuric acid or metal halide anions, the addition reaction of styrene monomers is the main reaction, resulting in polymers higher than oligomers. However, in the case of α-alkylstyrene monomers in which an alkyl group is substituted at the α-position of sterene, α
- Due to the steric hindrance of the alkyl group, it is difficult to grow more than a dimer, and a dimer is easily obtained. On the other hand, for styrene monomers that do not have an α-alkyl group, no method has been provided for dimerizing them with good yield, and only oligomers or mixtures of oligomers and high polymers have been obtained. As the reaction temperature increases, the proton elimination reaction is accelerated, and the reaction tends to stop at the dimer level, but at the same time, the amount of highly polymerized products due to radical polymerization increases, and saturated dimerization occurs due to intramolecular cyclization during proton elimination. body increases. As a result of research on the cationic polymerization of styrenes, the present inventors found that it has proton elimination properties to the extent that polymerization is terminated by dimerization, and that saturated dimers are generated by intramolecular addition upon proton elimination. The present invention was completed by discovering unique anions and temperature conditions. The amount of sulfonate anion to be used in the reaction system is preferably 0.1 to 200 mmole equivalent per mole of styrene. Although it can be used outside this range,
If the amount is too small, a satisfactory reaction rate cannot be obtained and reaction time is required, while if the amount is too large, it will require additional effort to remove the catalyst, which is economically disadvantageous. The reaction temperature can be selected as appropriate within the temperature range of more than 150°C, more preferably 20°C to 80°C.
Within the temperature range of ℃. If the temperature is below 0°C, oligomers of styrene trimers or higher or polymers with a higher degree of polymerization will be produced, while if the reaction temperature is high, the reaction rate will increase, but radical polymerization of styrene may occur. Since saturated dimers are produced and the selectivity for unsaturated dimers decreases, it is necessary to carry out the dimerization reaction at an appropriate temperature range of 150° C. or lower. The reaction of the present invention is preferably carried out in the presence of a solvent. Any solvent may be used as long as it does not stop the cationic polymerization of styrenes. Preferred specific examples of the solvent include aromatic compounds such as benzene, chlorobenzene, dichlorobenzene, trichlorobenzene, and nitrobenzene;
18, saturated aliphatic hydrocarbons such as n-hexane; saturated alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, trimethylcyclohexane, methylethylcyclohexane and decalin; or halides thereof. These include methylene chloride, chloroform, carbon tetrachloride, dichloroethane, trichloroethane, etc. Of course, the solvents that can be used in the present invention are not limited to the compounds specifically exemplified here. In addition, two or more types of solvents can also be used in combination. The reaction of the present invention is carried out under liquid phase reaction conditions,
Pressure can be applied as necessary to maintain the liquid phase. The unsaturated dimer can be isolated from the reaction mixture by vacuum distillation. According to the present invention, all of the styrene dimers produced are unsaturated dimers, and the yield thereof is extremely high. The present invention will be explained in more detail with reference to Examples below. Example 1 A benzene solution of trifluoromethanesulfonic acid (CF ₃ SO ₃ H) was added to a benzene solution of styrene in dry nitrogen, and the mixture was heated at a temperature of 50°C under the initial conditions of a styrene concentration of 0.50 mol/, a catalyst concentration of 0.20 mmol/
The reaction was allowed to proceed for 120 minutes. After terminating the reaction with ammoniacal methanol, the solvent and unreacted styrene were removed under reduced pressure at 40°C. The conversion rate was determined by quantifying unreacted styrene using gas chromatography. The yield of dimer in the product was determined from the molecular weight distribution of the product obtained by gel permeation chromatography. The produced dimer was confirmed to be almost a single component by gas chromatography, and its structure was determined to be 1,3-diphenyl-1 by NMR and IR.
- Confirmed to be butene. Table 1 shows the results. Examples 2 to 6 Table 1 shows the results of styrene dimerization reactions conducted in the same manner as in Example 1 by changing the catalyst, solvent, and temperature. In this case as well, the dimer produced was 1,3-diphenyl-1-butene.

[Table] Examples 7 and 8 Sterene was mixed with m-vinyltoluene (65%) and p-vinyltoluene (65%).
Instead of a mixture of vinyltoluene (35%), trifluoromethanesulfonic acid (CF ₃ SO ₃ H) and sodium trifluoromethanesulfonate and sulfuric acid (CF ₃ SO ₃ Na + H ₂ SO ₄ ) were added as catalysts.
Dimerization reactions of vinyltoluene were carried out in accordance with Examples 1 and 6 for two types of combinations of 10:1 (molar ratio). Each product is 1,3-
Bis(4-methylphenyl)-1-butene; 1,
3-bis-(3-methylphenyl)-1-butene;
1-(4-methylphenyl)-3-(3-methylphenyl)-1-butene; It is a mixture of 1-(3-methylphenyl)-3-(4-methylphenyl)-1-butene, and the conversion rate is 100wt%. The dimer yield is
It was 85wt%. Comparative Examples 1 to 3 In Comparative Example 1, styrene was reacted using the same catalyst as in Example 1 at a temperature of 0° C. or lower according to the method of Example 1. As is clear from the results in Table 2, only a small amount of dimer formation was observed. In Comparative Example 2, styrene was reacted using methanesulfonic acid, cyclohexanesulfonic acid, and p-toluenesulfonic acid as catalysts in the same manner as in Example 1 except for the catalytic amounts. As a result, in the presence of a sulfonate anion that does not contain a halogen atom, the activity was low and the yield of dimer in the product was low, with more than 30% of polymers of trimer or higher being formed. . In Comparative Example 3, α-methylstyrene was reacted in the same manner as in Example 1 using the same trifluoromethanesulfonic acid as in Example 1, and the dimer in the product was a cyclic saturated dimer. It was produced in large amounts, indicating that the reaction behavior was different for α-methylstyrene.

[Table] Comparative Examples 4 to 6 Styrene was prepared using conventionally known sulfuric acid, boron trifluoride (ethyl ether solution) (BF ₃ O (C ₂ H ₅ ) ₂ ), and solid acid (Galleon Earth 036 manufactured by Mizusawa Chemical). Table 3 shows the results of the reaction. As is clear from Table 3, in the case of sulfuric acid, formation of a considerable amount of saturated dimers and oligomers of trimers and higher was observed. In the case of boron trifluoride (ethyl ether solution) (BF ₂ O(C ₂ H ₅ ) ₂ ), no dimer was observed and most of the samples were oligomers of trimer or higher. Furthermore, in the case of solid acids (silica/alumina), the dimer yield is low, and the unsaturated component in the dimer is extremely low at 20%.

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Claims (1)

[Scope of Claims] 1. A styrene characterized by dimerizing a styrene represented by the following formula () in the presence of a sulfonate anion represented by the following formula () in a temperature range exceeding 0°C and not more than 150°C. A method for producing unsaturated dimers of the following types. (R is hydrogen or a lower alkyl group having 1 to 3 carbon atoms, n is the number of alkyl groups when R is an alkyl group and is 1 or 2, and when n is 2, R is the same or different alkyl group. Good.) R′SO ₃ ^- ………() (R′ is a fluorine atom, a chlorine atom, and a fluorine substituted product of an aliphatic hydrocarbon residue, an alicyclic hydrocarbon residue, or an aromatic hydrocarbon residue) (a substituent selected from the group consisting of , chlorine-substituted product, or bromine-substituted product).