Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1992-04-29
1993-11-23
Reamer, James H.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C07C 4554
Patent
active
052646335
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the preparation of 1,4-bis(4-hydroxybenzoyl)benzene by Fries rearrangement of diphenyl terephthalate in the presence of haloalkanesulfonic acid in solvents.
In J.A.C.S. 1938, p. 2283, Blicke et al. describe the rearrangement of diphenyl terephthalate in the presence of AlCl.sub.3 in carbon disulphide (CS.sub.2). After distilling off the solvent, the reaction mixture is heated to 185.degree.-190.degree. C. Following destruction of the aluminum complex with dilute hydrochloric acid, the product obtained is extracted with dilute aqueous sodium hydroxide solution. Final acidification then gives 1,4-bis(4-hydroxybenzoyl)benzene, which has a melting point of 297.degree.-299.degree. C. after recrystallization from alcohol. However, this synthesis route is unsuitable for industrial production because of disadvantages associated therewith, such as aluminum-containing wastewater and a plurality of side reactions owing to the considerably elevated temperature.
A process for the preparation of 1,4-bis(4-hydroxybenzoyl)benzene is known from EP 0,075,390 in which the target compound is prepared starting from phenol and terephthalic acid in fluoroalkanesulfonic acid as a solvent.
There was therefore a need for a process in which the catalyst system can be used in sub-stoichiometric amounts, easily worked up and recovered.
It has now been found that 1,,4-bis(4-hydroxybenzoyl)benzene of the formula I ##STR3## can advantageously be prepared by rearranging diphenyl terephthalate of the formula II ##STR4## in about 3 to about 50 parts, preferably about 5 to about 20 parts, relative to the diphenyl terephthalate, of an anhydrous organic solvent which is inert to the reactants, in the presence of haloalkanesulfonic acids (catalysts) of the general formula III chlorine atom, with the proviso that at least one X is a fluorine atom, and n is an integer from 1 to 10, at temperatures of about 10.degree. C. to about 200.degree. C., preferably of about 80.degree. C. to about 130.degree. C.
It is advantageous in the process according to the invention to work under oxygen-free conditions. As far as the pressure conditions are concerned, the reaction can be carried out at atmospheric pressure or alternatively at a slight overpressure, in particular at the autogenous pressure of the system, which is determined in particular by the temperature used, but also by other factors, such as the extent of filling of the reaction vessel. For example, the overpressure can be in the range up to 10 or 15 bar. If working at elevated pressure, the process can be carried out, for example, in a stainless steel autoclave, which if desired is coated with a resistant material, such as, for example, polytetrafluoroethylene. The reaction can be accelerated by the use of overpressure, but an increased formation of by-products can also be associated with this.
An advantage of the process according to the invention is that diphenyl terephthalate or phenol/terephthaloyl dichloride is added to the mother liquor obtained after the separation of the precipitated 1,4-bis(4-hydroxybenzoyl)benzene and thus the reaction medium can be reused many times, for example up to six times, without noticeable losses of yield occurring. In the case of too frequent recycling, concentration of by-products is observed so that it proves to be convenient to exclude about 20% by weight and to fortify with fresh catalyst. The excluded mother liquor can be worked up externally by known processes in order to recover the catalyst. A second possibility for working-up is the concentration of the reaction mixture by distilling off the solvent/catalyst mixture, which can likewise be fed back into the next reaction. Which of the two methods proves the most favorable depends on the solvent used and the haloalkanesulfonic acid employed. The crude 1,4-bis(4-hydroxybenzoyl)benzene separated off can be purified by treatment with alkali metal hydroxides and subsequent pH-controlled acidification and separated off from the co-formed half ester, which is fed back in
REFERENCES:
patent: 4827041 (1989-05-01), Ford et al.
patent: 5041616 (1991-08-01), Sumner
Blicke, F. F., et al, J. Am. Chem. Soc. 60:2283-2285 (1938).
Hackenbruch Joachim
Papenfuhs Theodor
Schneller Arnold
Hoechst Aktiengesellschaft
Reamer James H.
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