Process for the preparation of 1,4-bis(4-fluorobenzoyl)-benzene

Details Process for the preparation of 1,4-bis(4-fluorobenzoyl)-benzene Process for the preparation of 1,4-bis(4-fluorobenzoyl)-benzene

1992-11-25

1994-04-05

Reamer, James H.

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C07C 4546

Patent

active

053006933

DESCRIPTION:

BRIEF SUMMARY
The invention relates to an improved process for the preparation of 1,4-bis(4-fluorobenzoyl)benzene in high yield and purity by reaction of terephthaloyl chloride with fluorobenzene while metering in aluminum chloride or aluminum bromide at reaction temperatures below 70.degree. C.
1,4-Bis(4-fluorobenzoyl)benzene is a useful starting material for the preparation of high performance plastics, such as, for example, polyether ketosulfones, polyether ketones or laminated materials.
In spite of the use of novel Friedel-Crafts catalysts, such as hydrogen fluoride/boron trifluoride mixtures (DE-OS 3,806,656) or polyfluorinated alkanesulfonic acids (DE-OS 3,807,623), aluminum chloride still has great importance as a catalyst for the preparation of 1,4-bis(4-fluorobenzoyl)benzene from fluorobenzene and terephthaloyl chloride, as it is inexpensive, relatively easy to handle and has been thoroughly investigated with respect to its toxicological and ecological properties. preparation of 1,4-bis(4-fluorobenzoyl)benzene from fluorobenzene and terephthaloyl chloride in the presence of aluminum chloride is known in principle, a process for the preparation of 1,4-bis(4-chlorobenzoyl)benzene described in GB Patent 1,139,296 being referred to for experimental details In this process, excess chlorobenzene is reacted with terephthaloyl chloride and aluminum chloride in the molar ratio 13:1.0:2.3 at 130.degree. C. (boiling temperature of chlorobenzene) in the course of 6 h. Yield and purity are not given therein
The preparation of 1,4-bis(4-fluorobenzoyl)benzene from fluorobenzene and terephthaloyl chloride with the aid of AlCl.sub.3 is also described in DE-OS 3,531,837. In Example 1 therein, virtually the same molar ratios are used as in GB Patent 1,139,296 mentioned further above. However, according to Example 1 here, aluminum chloride is suspended in fluorobenzene and terephthaloyl chloride, dissolved in fluorobenzene, is then metered in, the temperature of the reaction mixture rising from 60.degree. C. to 85.degree. C. (boiling temperature of fluorobenzene).
In the abovementioned process of DE-OS 3,531,837, the reaction is thus at least partially carried out at the boiling temperature of fluorobenzene. However, the yield and purity given for the 1,4-bis(4-fluorobenzoyl)benzene in DE-OS 3,531,837 cannot be assessed, as after the purification more product is obtained (1250 g) than there was crude product present (1225 g.
In U.S. Pat. No. 4,820,791, J. Pol. Sci., Part A, Polymer Chemistry 25, 1093 (1987) and ACS, Polymer Prepr. 28, 92 (1987), Hergenrother et al. mention that 1,4-bis(4-fluorobenzoyl)benzene is accessible in the presence of AlCl.sub.3 from terephthaloyl chloride and fluorobenzene, but without going into experimental details. The yield according to these latter literature sources is a technically unsatisfactory 88% with a melting point of 218.5 to 219.5.degree. C.
Our own investigations showed that, according to the AlCl.sub.3 process described above, the 1,4-bis(4-fluorobenzoyl)benzene is only obtained in a purity (see the Comparison Examples 3 and 6) which does not meet the high demands on starting compounds for high performance polymers. Under the conditions mentioned, i.e. during the Friedel-Crafts reaction, the fluorobenzene is converted into chlorobenzene by the AlCl.sub.3. This can also be verified in a model experiment in which the fluorobenzene is treated with AlCl.sub.3 at temperatures of about 85.degree. C. (cf. Example 4). The chlorobenzene formed is enriched in excess fluorobenzene if this is not purified by complicated rectification before returning it. In the following reactions, this chlorobenzene inevitably reacts with terephthaloyl chloride analogously to fluorobenzene. A mixture of 1,4-bis(4-fluorobenzoyl)benzene, 1-(4-chlorobenzoyl)-4-(4-fluorobenzoyl)benzene and 1,4-bis(4-chlorobenzoyl)benzene is then obtained as the product, whose content of chlorine-containing bisbenzoylbenzenes increases with the amount of chlorobenzene in the fluorobenzene (cf. Examples 5 to 7).
This important fact for th

REFERENCES:
patent: 4820791 (1989-04-01), Hergenrother et al.
Patent Abstracts of Japan, Abstract of Kokai 62-103038, Oct. 15, 1987.

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