Method for preparing trimer of .alpha.-methyl styrene or derivatives thereof

A method for preparing a trimer of .alpha.-methyl styrene or derivatives thereof, wherein .alpha.-methyl styrene or derivatives thereof is added to an organic solvent comprising Lewis acid is provided. According to the method, the trimer of .alpha.-methyl styrene or derivatives thereof can be obtained in high yield.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method for preparing trimer of 
.alpha.-methyl styrene or derivatives thereof. 
2. Description of the Prior Art 
There have been known many methods for preparing an oligomer of 
.alpha.-methyl styrene or derivatives thereof, including a method using 
silver fuluoroborate (Japanese Patent Unexamined Application, hereinafter 
referred to as "J.P.KOKAI" No. Sho 50-157343), a method using an alkyl 
aluminum, a method using a salt of ultra strong acid (Japanese Patent 
Publication for Opposition Purpose, hereinafter referred to as 
"J.P.KOKOKU" No. Sho 57-10851), a method for treating .alpha.-methyl 
styrene in the presence of sulfonic acid type cation exchange resin under 
a given temperature (J.P.KOKOKU Hei 4-15771), a method for reacting 
.alpha.-methyl styrene with heteropoly acid in solid-liquid phase 
heterogeneous system in the absence of a solvent (J.P.KOKAI Hei 8-12601), 
a method using an oxygen-containing compound such as water, dihydric 
alcohol or ether as a reaction adjusting agent in the presence of a solid 
acid catalyst such as activated clay (J.P.KOKOKU Hei 8-23029). 
Polymer Journal, vol. 13, No. 10, p. 947-953 (1981) discloses a method for 
preparing dimer and trimer of .alpha.-methyl styrene by cation 
polymerization of .alpha.-methyl styrene in the presence of binary metal 
oxide such as Al.sub.2 O.sub.3 --TiO.sub.2. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide a method for 
preparing a trimer of .alpha.-methyl styrene or derivatives thereof, which 
permits the production thereof in a high yield. 
Another object of the present invention is to provide a method for 
preparing a trimer of .alpha.-methyl styrene or derivatives thereof, which 
permits the stable production thereof in a high yield. 
A still further object of the present invention is to provide a method for 
preparing a trimer of .alpha.-methyl styrene or derivatives thereof in a 
high yield more effectively. 
According to an aspect of the present invention, there is provided a method 
for preparing a trimer of .alpha.-methyl styrene or derivatives thereof, 
wherein .alpha.-methyl styrene or derivatives thereof is added to an 
organic solvent comprising Lewis acid. 
According to preferred embodiment of the present invention, a molar ratio 
of Lewis acid to the .alpha.-methyl styrene or derivatives thereof is 
0.0005-0.1, and a reaction temperature is between -15.degree. C. and 
30.degree. C. 
Preferably the Lewis acid is AlCl.sub.3. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
.alpha.-methyl styrene or derivatives thereof used in the present invention 
include .alpha.-methyl styrene, m- or p-methyl-.alpha.-methyl styrene, m- 
or p-ethyl- .alpha.-methyl styrene, m- or p-isopropyl-.alpha.-methyl 
styrene with .alpha.-methyl styrene being preferred because it is easily 
available. 
Lewis acids used in the present invention include Al.sub.2 O.sub.3, 
TiO.sub.2, ZnCl.sub.2, SnCl.sub.4, TiCl.sub.4, FeCl.sub.3, BF.sub.3, 
AlCl.sub.3 with AlCl.sub.3 being preferred. The Lewis acid may be used 
alone, but it is preferably used in the form of a solution in 
nitro-substituted alkane such as CH.sub.3 NO.sub.2 (nitromethane); 
aromatic nitro compounds such as nitrobenzene, o-nitro-toluene, 
m-nitro-toluene so that the reaction system becomes homogenous. In that 
case, a concentration of the Lewis acid in the solution is preferably 
5-25% by weight. This is because if the concentration of the Lewis acid is 
lower than 5% by weight, the speed of the reaction will decrease, while if 
it exceeds 25% by weight, it will be difficult to dissolve the Lewis acid 
homogeneously. 
It is essential in the method of the invention first to disperse or 
dissolve a catalyst, that is, Lewis acid such as AlCl.sub.3, AlCl.sub.3 
--CH.sub.3 NO.sub.2, or AlCl.sub.3 --C.sub.6 H.sub.5 NO.sub.2 in an 
organic solvent to prepare a solution of the acid in the solvent and then 
to add dropwisely .alpha.-methyl styrene or derivatives thereof (which may 
be dissolved in an organic solvent). If .alpha.-methyl styrene or 
derivatives thereof and the Lewis acid are mixed simultaneously in the 
organic solvent, or the Lewis acid or the Lewis acid dispersed or 
dissolved in the organic solvent is dropped into .alpha.-methyl styrene or 
derivatives thereof, or the organic solvent solution of the .alpha.-methyl 
styrene or derivatives thereof, the yield of a trimer of .alpha.-methyl 
styrene or derivatives thereof becomes low. 
A molar ratio of Lewis acid to .alpha.-methyl styrene or derivatives is 
preferably 0.0005-0.1, more preferably 0.001-0.05, and most preferably 
0.002-0.01. This is because if the molar ratio of the Lewis acid is lower 
than 0.0005, the speed and the rate of the reaction will decrease. While 
if it exceeds 0.1, the yield of the trimer will decrease. 
A reaction temperature is typically from -15 to 30.degree. C., preferably 
-10 to 20.degree. C., more preferably -10 to 10.degree. C. This is because 
if the reaction temperature is lower than -15.degree. C., the yield of the 
tetramer or higher oligomers which comprise more than four units of 
.alpha.-methyl styrene or derivatives thereof increases, and the yield of 
the trimer decreases. While if it exceeds 30.degree. C., the yield of the 
dimer of .alpha.-methyl styrene or derivatives thereof increases, and the 
yield of the dimer decreases. 
Organic solvents used in the reaction include saturated aliphatic 
hydrocarbon such as petroleum ether, hexane and methyl cyclohexane; 
aromatic hydrocarbon such as benzene, toluene and xylene; ether or 
derivatives thereof such as diethyl ether, dibutyl ether and 
tetrahydrofuran. 
If .alpha.-methyl styrene is used, a dimer of the formula (I) and a trimer 
of the formula (II) and (III) are obtained. 
##STR1## 
The trimer usually obtained is a mixture of the compound of the formula 
(II) and the compound of the formula (II) in a molar ratio of about 7:3. 
The foregoing chemical structures are confirmed by NMR (nuclear magnetic 
resonance), HPLC (high pressure liquid chromatography), GC-MS analysis 
(gas chromatography--mass spectrometry), etc. 
The trimer of .alpha.-methyl styrene or derivatives thereof obtained by the 
method according to the present invention can be used for various purposes 
such as a plasticizer for sealing materials and heat medium etc.

The present invention will hereinafter be described in more detail with 
reference to the following working Examples, but the present invention is 
not restricted to these specific Examples. 
EXAMPLE 1 
To a four-necked 200 ml-volume flask equipped with a stirring machine, a 
dropping funnel, a Dimroth condenser and a thermometer, there was placed a 
solution of 0.46 g of AlCl.sub.3 in CH.sub.3 NO.sub.2 (0.069 g of 
AlCl.sub.3 =0.517 mmol)(15% by weight) as Lewis acid, and 100 ml of 
toluene as an organic solvent. Then a toluene solution containing 30 g 
(254 mmol) of .alpha.-methyl styrene was placed in the dropping funnel (a 
molar ratio of AlCl.sub.3 to .alpha.-methyl styrene is 0.002). 
The temperature in the flask was kept to 0.degree. C., the toluene solution 
containing .alpha.-methyl styrene was dropwise added over 35 minutes into 
the flask with stirring. The stirring of the reaction system was continued 
for 25 minutes after the dropwise addition was completed. Then, water was 
gradually dropwise added to decompose the Lewis acid. After the organic 
layer was washed with water, the product was analyzed by HPLC (high 
pressure liquid chromatography). Almost 100% of .alpha.-methyl styrene was 
reacted and a ratio of the trimer was as high as 75%. The result was shown 
in Table 1. 
EXAMPLE 2 
The same procedures as in Example 1 were repeated except that 0.913 g of 
AlCl.sub.3 solution in CH.sub.3 NO.sub.2 (15% by weight) was used (a molar 
ratio of AlCl.sub.3 to .alpha.-methyl styrene was 0.004). The result was 
shown in Table 1. 
EXAMPLE 3 
The same procedures as in Example 1 were repeated except that 0.069 g of 
AlCl.sub.3 was used instead of the AlCl.sub.3 solution in CH.sub.3 
NO.sub.2. The reaction system was heterogeneous, however, the reaction 
progressed without problem. The result was shown in Table 1. 
EXAMPLE 4 
The same procedures as in Example 1 were repeated except that the reaction 
temperature was changed to 15.degree. C. The result was shown in Table 1. 
EXAMPLE 5 
To a four-necked 200 ml-volume flask equipped with a stirring machine, a 
dropping funnel, a Dimroth condenser and a thermometer, there was placed a 
solution of 0.12 g of AlCl.sub.3 in 0.40 g of nitrobenzene (0.12 g of 
AlCl.sub.3 =0.90 mmol)(23% by weight) as Lewis acid, and 100 ml of toluene 
as an organic solvent. Then a toluene solution containing 30 g (254 mmol) 
of .alpha.-methyl styrene was placed in the dropping funnel (a molar ratio 
of AlCl.sub.3 to .alpha.-methyl styrene is 0.0035). 
The temperature in the flask was kept at -7.degree. C., the toluene 
solution containing .alpha.-methyl styrene was dropwise added over 48 
minutes into the flask with stirring. The stirring of the reaction system 
was continued for 60 minutes after the dropwise addition was completed. 
Then, water was gradually dropwise added to decompose the Lewis acid. 
After the organic layer was washed with water, the product was analyzed by 
HPLC. Almost 100% of .alpha.-methyl styrene was reacted and a ratio of the 
trimer was as high as 75%. The result was shown in Table 1. 
EXAMPLE 6 
The same procedures as in Example 5 were repeated except that the 
temperature at the time of the stirring of 60 minutes was kept at 
0.degree. C. The result was shown in Table 1. 
EXAMPLE 7 
The same procedures as in Example 6 were repeated except that the 
concentration of AlCl.sub.3 solution in nitrobenzene was changed to 10% by 
weight, and the amount of the AlCl.sub.3 solution in nitrobenzene was 1.20 
g. The result was shown in Table 1. 
Comparative Example 1 
The same procedures as in Example 1 were repeated except that 100 ml of a 
toluene solution containing 30 g of .alpha.-methyl styrene (254 mmol) was 
placed in the flask, then 0.46 g of AlCl.sub.3 solution in CH.sub.3 
NO.sub.2 (15% by weight) and 50 ml of toluene were placed in the dropping 
funnel, and the catalyst (AlCl.sub.3 solution in CH.sub.3 NO.sub.2) was 
dropwise added into the .alpha.-methyl styrene solution (a molar ratio of 
AlCl.sub.3 to .alpha.-methyl styrene was 0.002). The result was shown in 
Table 1. 
The formation of dimer and trimer was confirmed by .sup.1 H-NMR analysis of 
fractions obtained from GC-MS analysis and HPLC. 
TABLE 1 
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Molar ratio Reaction Reaction 
of AlCl.sub.3 to .alpha.-methyl temperature rate 
styrene (.degree. C.) (%) 
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Example 1 0.002 0 98.5 
Example 2 0.004 0 99.9 
Example 3 0.002 0 98.0 
CH.sub.3 NO.sub.2 not used 0 
Example 4 0.002 15 99.1 
Example 5 0.0035 -7 99.9 
Example 6 0.0035 0 99.9 
Example 7 0.0035 0 99.9 
Comparative 0.002 0 98.3 
Example 1 catalyst was added 
into the monomer 
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The ratio of the product 
(% of peak area in HPLC) 
dimer trimer tetramer 
pentamer and more 
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Example 1 15 75 8 2 
Example 2 18 75 5 2 
Example 3 21 73 3 3 
Example 4 21 72 6 1 
Example 5 7.5 75 15 2.5 
Example 6 24 70 5.5 0.5 
Example 7 8 70 17 5 
Comparative 33 45 12 10 
Example 1 
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As has been discussed above in detail, the method for preparing trimer of 
.alpha.-methyl styrene or derivatives thereof according to the present 
invention permits the production of the trimer of .alpha.-methyl styrene 
or derivatives thereof in high yield.