Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Reexamination Certificate
2001-02-14
2002-04-30
Shaver, Paul F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
C556S480000, C570S129000
Reexamination Certificate
active
06380415
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for producing octafluoro[2,2]paracyclophane, which is useful as an intermediate for functional materials. This compound is particularly useful as a raw material for a heat-resistant parylene polymer film.
There are several processes for producing octafluoro[2,2]paracyclophane. J. Org. Chem. 1970, 35, 20-22 discloses a process for producing this target compound with a yield of 9-28% by a pyrolytic dimerization of a compound represented by the general formula (1) at a temperature of 600-800° C.,
where X is chlorine, bromine or SO
2
R′ where R′ is an alkyl group. U.S. Pat. No. 5,210,341 discloses a process for producing the target compound with a yield of 32% by a reductive dimerization of the compound represented by the general formula (1) where X is bromine, by TiCl
4
—LiAlH
4
at 70° C. There is another process for producing the target compound by a reductive dimerization of the compound represented by the general formula (1) wherein X is bromine, by a combination of Bu
3
SnSiMe
3
and CsF (see J. Org. Chem., 1997, 62, 7500-7502 and J. Org. Chem., 1999, 64, 9137-9143).
WO 98/24743 discloses a process for producing 1,4bis(difluoromethyl)benzene by the steps of (a) chlorinating paraxylene to obtain 1,4-bis(dichloromethyl)benzene and (b) fluorinating this compound by a metal fluoride into the target product. In this publication, it is proposed that 1,4-bis(dichloromethiyl)benzene is fluorinated with CsF or KF under a slurry condition at a temperature of 180° C. or higher.
Chemical Abstract, Vol. 124, 116848 discloses a process for producing 1,4-bis(trifluoroemthyl)benzene by fluorinating 1,4-bis(dibromomethyl)benzene by antimony trifluoride in the absence of solvent under a condition of 100-150° C. and 20-100 mmHg.
J. Am. Chem., Soc., 82, 543 (1960) discloses a fluorination of terephthalaldehyde by sulfur tetrafluoride at 150° C. French Patent 2109416 discloses a fluorination of terephthalaldehyde by molybdenum fluoride and boron trifluoride.
It is disclosed in J. Chem. Soc., Chem. Commun., 1993, 678 that 1-trifluoromethyl-4-difluorotrimethylsilylmethylbenzene can be synthesized by a silylmethylation of bis(trifluoromethyl)benzene through a photo-inducing reaction using tetramethyldisilane.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for producing octafluoro[2,2]paracyclophane with a high yield, using La raw material that is easily available.
According to the present invention, there is provided a process for producing octafluoro[2,2]paracyclophane. This process comprises:
reacting 1,4-bis(trifluoromethyl)benzene with a halogenated silane represented by the general formula (1), in the presence of a low valence metal, thereby obtaining a compound represented by the general formula (2); and
conducting in the presence of a fluoride ion a dimerization of said compound into said octafluoro [2, 2]p aracyclophane,
R
3
SiX (1)
where each R is independently an alkyl group or aryl group, and X is a halogen atom,
where R is defined as above.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The inventors have eager examined a dimerization of 1,4-bis(trifluoromethyl)benzene by removing fluorine atom from this compound. In this examination, we unexpectedly found that it is possible to easily break C-F bond, which is generally difficult to be broken due to its large bonding energy, of 1,4-bis(trifluoromethyl)benzene by setting a special intermediate (as a precursor of octafluoro[2,2]paracyclophane), that is, the compound represented by the general formula (2), and that it is possible to produce octafluoro[2,2]paracyclophane by a dimerization of this compound.
Hereinafter, the reaction of 1,4-bis(trifluoromethyl)benzene with the halogenated silane may be referred to as the first step, and the dimerization may be referred to as the second step.
The halogenated silane used in the first step is not particularly limited. In the general formula (1) representing the halogenated silane, the alkyl group (R) may be a lower alkyl group (e.g., methyl group, ethyl group, propyi group, or isopropyl group), and the aryl group (R) may be phenyl group or tolyl group. Furthermore, X may be chlorine, bromine or. iodine. Preferable examples of the halogenated silane are chlorotrimethylsilane, chlorotriethylsilane, chlorophenyldimethylsilane, chlorodiphenylmethylsilane, and bromotriethylsilane. Of these, chlorotrimethylsilane is the most preferable, since it is easily available.
The amount of the halogenated silane to be used in the first step may be 1 mole or greater (from the viewpoint of stoichiometry), preferably about 1-50 moles, more preferably about 1-10 moles, per mole of 1,4-bis(trifluoromethyl)benzene.
It is optional to use a solvent in the first step, as long as the solvent is inert under reaction conditions of the first step. Examples of such solvent are aliphatic hydrocarbons (e.g., pentane, hexane and heptane), aromatic hydrocarbons (e.g., benzene, toluene and xylene), nitrites (e.g., acetonitrile, propionitrile, phenylacetonitrile, isobutyronitrile, and benzonitrile), acid amides (e.g., N,N-dimethylformamide, N,N-dimethylacetoamide, methylformamide, formamide, hexamethylphosphoric acid, and hexamethyl phosphoric acid triamide), and lower ethers (e.g., tetrahydrofuran, 1,2-dimethoxyethane, diglyme, triglyme, diethyl ether, 1,2-epoxyethane, 1,4-dioxane, dibutyl ether, t-butyl methyl ether, and substituted tetrahydrofuran). Of these, N,N-dimethylformamide and tetrahydrofuran are preferable. It is optional to use a mixture of at least two of these solvents. The solvent may be in an amount of about 1-100 parts by weight, preferably 1-20 parts by weight, per one part by weight of the 1,4-bis(trifluoromethyl)benzene.
It is preferable to remove water as much as possible from the solvent to be used in the first and second steps. It is, however, not necessary to remove water completely. The amount of water generally contained in a commercially available solvent is acceptable in the first and second steps. Therefore, it is possible to directly use a commercially available solvent in the invention, without removing water.
The low valence metal used in the first step is not particularly limited. In this specification, the low valence metal can be defined as being an element that belongs to typical elements and as being a metal that does not have an oxidation number of 5 or greater under a normal condition. It may be a metal element, for example, selected from magnesium, zinc, copper, iron, cadmium, tin, titanium, and sodium. Furthermore, the low valence metal may be in the form of a metal alloy containing at least one of these metal elements as a major component. Examples of such metal alloy ate an alloy of zinc and copper, Raney nickel, an alloy of silver and zinc, and an alloy of copper and magnesium. Furthermore, metal ion in a low oxidation state may also be applicable, such as titanium trichloride, samarium diiodide, and chromium dichloride. Furthermore, such metal ion in a low oxidation state may be in the form of a metal complex such as sodium naphthalenide, sodium benzophenon ketyl complex, or tetrakis(triphenylphosphine)palladium. Still furthermore, the low valence metal may be in the form of a mixture of the metal element or the metal alloy and the metal compound or the metal complex. Examples of such mixture are a mixture of titanium tetrachloride and metallic zinc, a mixture of titanocene dichloride and zinc, a mixture of samarium diiodide and samarium, and a mixture of samarium diiodide and magnesium. Of these, it is preferable to use magnesium or a mixture containing magnesium.
When the low valence metal is used in the form of a metal element (metallic form), its shape is not particularly limited. In fact, it may be in the form of powder, granules, aggregates, porous solid, chips or rod. For example, it is possible to directly use a magnesium having a known shape generally used for Grignard reaction.
Amii Hideki
Uneyama Kenji
Central Glass Company Limited
Crowell & Moring LLP
Shaver Paul F.
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