Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
2000-04-19
2003-01-14
Siegel, Alan (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
Reexamination Certificate
active
06506951
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing brominated trifluoromethylbenzenes, which can be used as intermediates for medicines and agricultural chemicals.
It is known that an aromatic compound having a bromine atom(s) on its aromatic ring can be obtained by brominating its corresponding aromatic compound. Japanese Patent Unexamined Publication 50-76029 and J. Am. Chem. Soc. Vol. 69, page 947 (1947) disclose a process for producing 3-bromotrifluoromethylbenzene by brominating a trifluoromethylbenzene by bromine in the presence of iron powder or iron chloride. Zh. Org. Ehim. Vol. 27, No. 1, page 125 discloses a process for producing 3bromo-trifluoromethylbenzene by brominating a trifluoromethylbenzene using sulfur tetrafluoride, hydrogen fluoride and bromine. Zh. Prikl. Khim. Vol. 46, No. 9 (1973)page 2012 discloses a process in which 1,3-bis(trifluoromethyl)benzene is simultaneously reacted with chlorine and bromine in the presence of antimony pentachloride, thereby obtaining 3,5-bis(trifluoromethyl)bromobenzene (selectivity: 74.1%) and 3,5-bis(trifluoromethyl)chlorobenzene (selectivity: 24.6%). J. Am. Chem. Soc. Vol, 72 page 1651 (1950) discloses a process in which 1,3-bis(trifluoromethyl)benzene is simultaneously reacted with chlorine and bromine in the presence of a catalytic amount of antimony pentachloride, thereby obtaining 3,5-bis(trifluoromethyl)bromobenzene (conversion: 70%, selectivity: 74.1%). Japanese Patent Unexamined Publication 9-169673 discloses a process in which 1,3-bis(trifluoromethyl)benzene is brominated by N-bromoimide in the presence of a strong acid, thereby obtaining 3,5-bis(trifluoromethyl)bromobenzene.
Bromine is strong in metal corrosiveness. Therefore, bromination is usually conducted in a glass reactor. However, if it is tried to brominate an aromatic compound having a trifluoromethyl group(s), the bromination does not easily occur due to the electron attractive property of the trifluoromethyl group(s). Therefore, it is necessary to make the reaction condition relatively severe to get the bromination. With this, the trifluoromethyl group may be decomposed by Lewis acid catalyst used in the bromination, thereby generating hydrogen fluoride in the reaction system. This hydrogen fluoride tends to corrode glass. Therefore, it has been necessary to avoid using glass as a reactor for conducing the bromination of the above aromatic compound or to conduct such bromination with an extra care using a glass reactor.
Of conventional Lewis acid catalysts, antimony pentachloride is high in reactivity and satisfactory in selectivity. It is, however, high in corrosiveness against metal. Furthermore, antimony compounds are highly soluble in organic matters, resulting in difficulty in separating those from the product. Even if they are separated by washing, it becomes troublesome to treat waste water after the washing.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for producing a brominated trifluoromethylbenzene from a trifluoromethylbenzene with high conversion and high selectivity.
According to a first aspect of the present invention, there is provided a first process for producing a brominated trifluoromethylbenzene represented by the general formula (1). The first process comprises brominating in a liquid phase a trifluoromethylbenzene, represented by the general formula (2), by bromine in the presence of an iron containing catalyst under a condition that the bromine is coexistent with chlorine,
where n is an integer of 1-2, and m is an integer of 1-3
Where n is an integer of 1-2.
According to a second aspect of the present invention, there is provided a second process for producing a brominated trifluoromethylbenzene represented by the general formula (1). The second process comprises brominating in a gas phase a trifluoromethylbenzene, represented by the general formula (2), by bromine in the presence of a catalyst under a condition that the bromine is coexistent with chlorine.
DESCRIPTION OF THE REF:ERRED EMBODIMENTS
It is possible to produce a brominated trifluoromethylbenzene represented by the general formula (1) from a trifluoromethylbenzene represented by the general formula (2) with high conversion and high selectivity by both of the first and second processes.
According to the fist process, both selectivity and conversion become high by using an iron-containing catalyst such as an iron halide, particularly iron chloride, since this catalyst has a high activity in the bromination. Furthermore, the catalyst is less soluble in the product. Therefore, the catalyst can easily be separated from the product by a simple operation such as decantation, thereby simplifying the process. The separated catalyst can be used repeatedly in the bromination. Still furthermore, the iron-containing catalyst has a low corrosiveness against metal. With this, the first process can be conducted in a metal reaction vessel. Thus, the first process is a desirable process for producing the brominated trifluoromethylbenzene in an industrial scale.
According to the second process, the bromination is conducted in a gas phase, thereby simplifying the process. Furthermore, the bromination of the second process can proceed efficiently by using a catalyst containing a metal chloride (e.g., iron chloride) carried on a carrier. This catalyst has a high activity and a long lifetime in the bromination. Therefore, it is possible to produce the brominated trifluoromethylbenzene from the trifluoromethylbenzene with high conversion and high selectivity. Thus, the second process has a superior operationability and a high productivity. Furthermore, it is possible to substantially prevent corrosion of a metal reaction vessel, because bromine and chlorine are treated in a vapor phase. Thus, the second process is also a desirable process for producing the brominated trifluoromethylbenzene in an industrial scale.
In the first and second processes, the trifluoromethylbenzene represented by the general formula (1) may be trifluoromethylbenzene, 1,4-bis(trifluoromethly)benzene, 1,3-bis(trifluoromethyl)benzene, or 1,2-bis(trifluoromethyl)benzene, and may be one prepared by any process. For example, Ind. Eng. Chem. 39 [19473] 302 discloses a method for producing 1,3-bis(trifluoromethyl)benzene. This method includes the steps of (a) chlorinating methaxylene to 1,3-bis(trifluoromethyl)benzene and (b) fluorinating the 1,3-bis(trifluoromethyl)benzene by hydrogen fluoride in the absence of catalyst at a temperature of 150-20° C. J. Am. Chem. Soc. 71 [1949] 1490 discloses the same method except that the step (b) is conducted in the presence of antimony pentachloride catalyst at room temperature.
In the first and second processes, the amount of bromine used may vary depending on the amount of the brominated trifluoromethylbenzene to be produced, and is 0.5 m (m is an integer of 1-3 in the general formula (1)) moles or more for each m number. In order to produce a monobromtrifluoromethylbenzene, the amount of bromine can be 0.5 moles or more, preferably 0.5-2 moles, more preferably 0.5-1 mole, still more preferably 0.5-0.75 moles, per mole of the trifluoromethylbenzene. Alternatively, the amount of bromine can be 0.5 moles or less per mole of the trifluoromethylbenzene in order to suppress the production of polybrominated compounds generated in the course of the complete bromination of the trifluoromethylbenzene.
In the first process, chlorine is used in an amount of 1 mole or more per mole of bromine. In fact, it suffices to use 1 to about 2 moles of chlorine per mole of bromine. Furthermore, it can be adjusted to 1 to about 1.2 moles by suitably controlling the reaction. If the amount of chlorine is less than 1 mole, conversion of bromine may become too low. If chlorine is used too much, it may cause the production of chlorinated trifluoromethylbenzenes and may lower the yield of the brominated trifluoromethylbenzene. Furthermore, it makes difficult to treat chlorine during the reaction.
In the first proces
Kaneda Shozo
Kume Takashi
Narizuka Satoru
Tsukada Eri
Ujiie Mikio
Central Glass Company Limited
Siegel Alan
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