This invention relates to polyfluorinated aromatic and heterocyclic compounds and methods for their production; specifically, the invention is concerned with compounds which contain sulphurpentafluoride groups.

The preparation and use of various polyfluorinated aromatic and heterocyclic derivatives is well documented in the prior art, and the compounds in question have found widespread use, for example as intermediates in the pharmaceutical industry.

Of particular value in this connection are intermediates containing trifluoromethyl groups, especially trifluoromethylbenzene derivatives ; a favoured end-group in this context is a 3,5-bis (trifluoromethyl) phenyl group which has been developed for use in a range of anti-asthma and anti-arthritis drugs. Such a group may be introduced into a drug molecule by means of a suitable labile group in the 1-position so that, for example, 3,5-bis (trifluoromethyl) bromobenzene is a useful intermediate for the preparation of such drugs.

The present inventors have now found that alternative polyfluorinated derivatives may be obtained by relatively straightforward synthetic procedures to provide a further range of intermediates with potentially widespread industrial applicability, particularly in relation to pharmaceuticals.

Various organic sulphur pentafluorides, and methods for their preparation, have previously been disclosed in PCT Patent Application WO 97/05106. The present inventors have now found that specific derivatives of this type are of particular value in the synthesis of pharmaceuticals ; such derivatives comprise trisubstituted compounds comprising at least one sulphur pentafluoride group and at least one labile group.

Thus, according to a first aspect of the present invention, there is provided a polyfluorinated aromatic or heterocyclic compound comprising at least three ring

substituents, at least one of which comprises a sulphurpentafluoride group and at least one of which comprises a labile group.

Said aromatic or heterocyclic compound may be based on any suitable ring system, but particularly favourable results may be obtained with compounds based on aromatic ring systems such as benzene, naphthalene, anthracene or phenanthrene, with benzene derivatives being especially preferred. Of particular value are trisubstituted benzene derivatives, substituted in the 1-, 3-and 5-positions.

Said polyfluorinated aromatic or heterocyclic compound comprising at least three ring substituents, at least one of which comprises a sulphurpentafluoride group and at least one of which comprises a labile group preferably includes one or two sulphurpentafluoride groups. Compounds which comprise only one sulphurpentafluoride group typically also comprise a further fluorinated group, preferably a trifluoromethyl group.

The labile group comprises a substituent capable of facilitating further reaction with another compound during, for example, drug production. Suitable reactive groups in the context of the compounds of the present invention are groups which are labile as a result of the powerful electron-withdrawing inductive effect of the polyfluorinated groups in the molecule, typical examples being amino, bromo and nitro groups.

Specifically preferred compounds according to the present invention are (3-amino-5- (trifluoromethyl) phenyl) sulphurpentafluoride, (3-bromo-5- (trifluoromethyl) phenyl) sulphurpentafluoride, (3-nitro-5- (trifluoromethyl) phenyl) sulphurpentafluoride, 3,5- bis (pentafluorosulphuryl) aniline, 3,5-bis (pentafluorosulphuryl) bromobenzene and 3,5-bis (pentafluorosulphuryl) nitrobenzene.

The present invention also envisages methods applicable to the preparation of the compounds of the first aspect of the present invention. Thus, according to a second aspect of the present invention, there is provided a method of preparation of a

polyfluorinated aromatic or heterocyclic compound comprising at least three ring substituents, at least one of which comprises a sulphurpentafluoride group and at least one of which comprises a labile group, said method comprising: (a) treating an aromatic or heterocyclic compound comprising at least two ring substituents, at least one of which comprises a disulphide or thiol group, with fluorine; and (b) introducing a labile group into said fluorinated precursor.

Preferably, said treatment with fluorine is carried out using gaseous elemental fluorine.

Thus, for example, bis (3-trifluoromethyl) disulphide has been successfully fluorinated by treatment with elemental fluorine to give 3- (trifluoromethyl) phenyl sulphurpentafluoride and, in a similar fashion, 1, 3-bis (pentafluorosulphuryl) benzene has been obtained from the direct fluorination of benzene-l, 3-dithiol.

Following the fluorination of the at least one disulphide or thiol group in the starting material, the fluorinated precursor is further reacted in order to introduce a labile group into the molecule, said group being capable of further reaction with another compound to facilitate introduction of the fluorinated moiety into a larger molecule such as a drug molecule. Said labile group may be introduced by treatment of the fluorinated precursor with any suitable reagent which is capable of introducing such a labile group into a vacant position on the aromatic or heterocyclic ring.

As previously observed, particularly suitable labile groups in this context comprise amino, bromo or nitro groups, all of which may be conveniently introduced into the fluorinated precursor. Thus, a nitro group may be introduced into the molecule by direct nitration ; this group may then optionally be reduced to provide the corresponding amino derivative. Alternatively, a bromo group may be substituted

into the ring by direct bromination. This may, for example, be carried out by reacting the fluorinated precursor with bromine in the presence of elemental fluorine.

Specifically, by way of example, the preparation of (3-bromo-5- (trifluoromethyl) phenyl) sulphurpentafluoride has been achieved by the direct bromination of 3- (trifluoromethyl) phenylsulphurpentafluoride in the presence of elemental fluorine, and 3,5-bis (pentafluorosulphuryl) bromobenzene has been similarly obtained from 1,3-bis (pentafluorosulphuryl) benzene.

Both (3-bromo-5- (trifluoromethyl) phenyl) sulphurpentafluoride and 3,5-bis (pentafluorosulphuryl) bromobenzene find particular application as intermediates for the preparation of medicaments for the treatment of, for example, asthma and arthritis.