Trihalomethylpyridine Compounds

Patentamt JEuropaisches ® Publication number: 0 1 07 866 9 European Patent Office B 1 Office europeen des brevets

(§) Dateof publication of patent specification: 30.03.88 © Int. CI.4: C 07 D 213/61 ^) Application number: 83110864.2

(22) Date of filing: 26.07.78 (§j) Publication number of the earlier application in accordance with Art. 76 EPC: 0 021 453

(§) Trihalomethylpyridine compounds.

INDUSTRIES (§) Priority: 12.08.77 GB 3403977 ® Proprietor: IMPERIAL CHEMICAL 26.10.77 GB 4454177 PLC 09 02 78 GB 523078 Imperial Chemical House Millbank London SW1P3JF(GB)

(43) Dateof publication of application: 09.05.84 Bulletin 84/19 ® Inventor: Cartwnght, David 1 Stonehaven Drive Woodley Reading Berkshire (GB) (45) Publication of the grant of the patent: 30.03.88 Bulletin 88/13 _ (74) Representative: Houghton, Malcolm... , John , .. et al@ Imperial Chemical Industries ® Designated Contracting States: PLC Legal Department: Patents PO Box 6 BE CH DE FR GB LU NL SE Welwyn Garden City Herts, AL7 1 HD (GB)

(58) References cited: (58)^ References cited: EP-A-0 000483 DE-A-2 223 894 EP-A-0 002 800 DE-A-2 812 571 EP-A-0 009 212 DE-A-2 812 607 BE-A- 857 022 DK-A- 326 078 BE-A-862325 FR-A-2236 861 CH-D- 947 176 278 675 FR-A-2288 089 FR-A-2406 629 The file contains technical information FR-A-2 406 630 submitted after the application was filed and GB-A-1 421 619 not included in this specification GB-A-1 424 359 Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1 ) European patent convention). Courier Press, Leamington Spa, England. ) 107 866 i) References cited: GB-A-2 045 245 US-A-2 516402 US-A-2 679 453 US-A-3244 722 US-A-3 244 722 US-A-3412095 US-A-3418 323 US-A-3 420 833 US-A-3461 125 US-A-3 732 230 US-A-4205175 US-A-4309 548 US-A-4317 913

HELVETICA CHIMICA ACTA, vol. 59, f asc. 1 , no. 23-24, 1976, pages 229-230 F. MUTTERER et al.: Halogenierte Pyridine V. Fluorierte und bromierte Pyridinverbindungen" Wc Bee et al, Ind. Eng. Chem; 1947, 39, 389 Vlalthes et al (Angew. Chem. Internat. Edit., 1963,2, 144 =ritz et al., Helvetica Chimica Acta, 1976, 59, 179-190 =laatsch J. Org. Chem., 27, 1406, 1962 107 bbb

Description divided This application is divided from Application No. 80103907.4 (EP— A— 0 021 453) which is itself from Application No. 78300203.3 (EP— A— 0 001 473). The present invention relates to a process for preparing certain trihalomethylpyndine compounds useful in the preparation of compounds having herbicidal properties, and to the novel compounds, 2,3- dichloro-5-trichloromethylpyridine and 2,3-dichloro-5-trifluoromethylpyridine. According to the present invention there is provided a process for preparing a compound of formula (II)

5 wherein X is chlorine or fluorine, Y is hydrogen or cnionne ana c. is imiuuiumeu.yi «. difluoromethyl, characterised by fluorinating a compound of formula (II')

vherein Y is hydrogen or chlorine. The invention also includes the novel compound, 2,3-dichloro-5-trichloromethylpyndine

to and the novel compound, 2,3-dichloro-b-tritiuorometnyipyriaine

States Patent The compound 2,3-dichloro-5-trichloromethylpyridine is mentioned by name in United Specification No. 3,244,722 but no method is disclosed by which it can be prepared. the formula The compounds of formula (II) are useful in the preparation of herbicidal compounds of (I) 40

^0_^J_0-CH-R2

45 wherein Z is trifluoromethyl or chlorodifluoromethyl; Y is hydrogen or chlorine; n is nyorogen or h_4 alkyl; and R2 is cyano; carboxy; carboxamido of formula — CNR3R4 II 50 O

wherein R3 is hydrogen or alkyl and R4 is hydrogen, optionally nyaroxy- or pnenyi-suubiuuwu 0,-4 a *y , R is or C, alkyl, phenyl or chlorophenyl, Cw alkoxy or a group of formula NRSR6 wherein hydrogen f NR3R4 constitutes pyrrolidine, pipendmo, or 55 and R6 is hydrogen, C,-4 alkyl, phenyl or chlorophenyl, or — morpholino; a group of formula — CSR7

bears wherein R7 is alkyl or phenyl; alkoxycarbonyl optionally substituted with hydroxy, alkoxy, halogen or a groupnrnun ofnf formula (I)(li wherein KR2 is — C— 0— ;

65 0 107 866

a group of formula — C(0CH2CH2)„0R8 II 0

5 wherein R8 is a C,_4 alkyl and n is an integer of 1 to 5; optionally halo- or methyl-substituted cyclohexyioxy- carbonyl; (C3_6 alkenyloxy)carbonyl; optionally halo- or methyl-substituted phenoxycarbonyl; or benzyloxycarbonyl, the phenyl group of which being optionally substituted with halogen or methyl; or, in the case of compounds wherein R2 is carboxy, salts thereof. When R3 is alkyl it is preferably d-,2 alkyl, for example alkyl. w When R7 is alkyl it is preferably Ci-Z0 alkyi, especially C,-^ alkyl, for example methyl, ethyl, propyl, butyl and dodecyl. When R2 is alkoxycarbonyl, it is preferably {C,^ alkoxy)carbonyl especially (Cn_12 alkoxy)carbonyl and particularly (C-,_8 alkoxy)carbonyl; for example the alkoxy moiety may be methoxy, ethoxy, propoxy, butoxy, /sobutoxy, secbutoxy, and octyloxy. is Salts of those compounds wherein R2 is carboxy may be prepared by conventional methods known for the preparation of salts of carboxylic acids. Typical salts include metal salts and ammonium salts. Metal salts include salts formed with alkali metal cations, for example sodium, potassium and lithium, and alkaline earth metal cations, for example calcium, strontium and magnesium. Ammonium salts include salts formed with the ammonium cation or with a mono-, di-, tri, or tetra-substituted ammonium cation in 20 which the substituents may be, for example, C-,-6 aliphatic radicals, for example, C-,-6 alkyl. One group of compounds includes those in which the group Z is CF3, Y is hydrogen, R1 is methyl, and R2 is as defined above. Within this group, R2 may be, for example, carboxy either as such or in the form of a salt thereof, or may be alkoxycarbonyl, for example, Ci-e alkoxycarbonyl. 25 Another group of compounds includes those in which the group Z is CF3, Y is chlorine, R1 is methyl and R2 is as defined above. Within this group, R2 may be, for example, carboxyl either as such or in the form of a salt thereof, or may be alkoxycarbonyl, for example C-,-6 alkoxycarbonyl. A further group of compounds includes those in which the group Z is chlorodifluoromethyl, R1 is a methyl group, and R2 is as defined above. Within this group of compounds, R2 may be, for example, 30 carboxy either as such or in the form of a salt thereof, or may be alkoxycarbonyl, for example C,-6 alkoxycarbonyl. These herbicidal pyridine compounds are among the compounds described in European Patent Application No. 78300203.3 (Publication No. 001,473) wherein herbicidal processes and compositions utilising the compounds are described. 35 Three general routes (described below as Routes, A, B and C) are available for the preparation of the herbicidal pyridine compounds from compounds of the formula (II)

wherein X, Y and Z are as defined above.

4 0 107 866

toute A is outlined in the following scheme.

Route A

OCH„

� o

(II) \ '5

^N� ft~^> 20 r O — V___7 — 3

(in

25 z Y Demethylating agent ^Y^^y^ ( III ) e.g. Pyridine — • — un ^ j 30 hydrochloride IV)

35 1 R i <>> lV) ^ Hal-CH-R2

40 V)

i-iai is In Route A, the symbols R , Rz, X, Y and Z have the meanings previously assigned to tnem, 45 halogen, preferably chlorine or bromine, and M is a cation, for example sodium. In Route A, the suitably substituted halogeno pyridine (II) is reacted with a metal salt of p- methoxyphenol. The reaction is preferably carried out in a solvent or diluent, for example methyl ethyl ketone, tetrahydrofuran, dimethylsulphoxide or dimethylacetamide. The 2-p-methoxyphenoxy compound (III) so obtained is then demethylated by a standard procedure, for example by heating with pyridine so hydrochloride or with hydrogen bromide in acetic acid, to obtain the corresponding p-hydroxy compound the sodium potassium salt) with the (IV) . This in turn is reacted in the form of its metal salt (for example or appropriate halogeno-alkanoic acid derivative (V) to obtain the required compound (I). Preferably this reaction is carried out in a solvent or diluent, for example methyl ethyl ketone.

55 Route B is outlined in the following scheme:—

(||) + HO 0H Base^ (IV) 60

65 (IV) + Hal-CH-R Base (I;

o 9 107 866

According to Route B, the appropriately substituted 2-halogenopyridme (II) is reacted with hydroquinone in the presence of a base to give the p-hydroxyphenoxy compound (IV) already referred to in Route A. The reaction is preferably carried out in a solvent or diluent for the reactants. Examples of suitable solvents include aprotic solvents, for example dimethylformamide. The reaction is preferably accelerated 5 by heating, for example to a temperature in the range from 50 to 150°. The base used in the reaction may be, for example, an inorganic base, for example sodium or potassium carbonate. The second stage of route B is identical with the last stage of Route A and requires no further description. 'O Route C

'5 3ase^ (I) (VI)

20 According to Route C, the appropriately substituted 2-halogenopyridine (II) is reacted with a 2-{p- hydroxyphenoxy)propionic acid derivative (VI) in the presence of a base, giving the compound of the invention (I) directly. The derivatives (VI) are known in themselves or may be made by conventional methods. The reaction is preferably carried out in the presence of a solvent or diluent for the reactants. Examples of solvents include lower ketones, for example methyl ethyl ketone. The reaction may be 25 accelerated by heating and may for example be conveniently carried out at the reflux temperature of the solvent. Examples of bases for use in the reaction include inorganic bases, for example anhydrous potassium carbonate. The substituted pyridine (II) used in Routes A, B and C may be prepared by reacting the compound of formula (II')

^N^^CI

35 wherein Y is hydrogen or chlorine, with a fluorinating agent so as to exchange some or all of the chlorine atoms for fluorine atoms. Thus 2-chloro-5-trifluoromethylpyridine is obtainable by reacting 2-chloro-5- trichloromethylpyridine with a fluorinating agent, for example antimony trifluoride or liquid hydrogen fluoride. By regulating the amount of fluorinating agent used in the reaction it is possible to obtain either the 5-trifluoromethyl- or 5-chlorodifluoromethyl- compounds; for example, 2-chloro-5-trichloromethyl- 40 pyridine (the subject of European Patent No. 0,021,453, based on an application derived from Application No. 78300203.3) may be reacted with a limited amount of antimony trifluoride to obtain 2-chloro-5-chlorodifluoromethylpyridine. In these halogen exchange reactions a proportion of the chlorine substituent at the 2-position of the pyridine may also exchange, so that a proportion of the 2-fluorinated compound may be obtained. This is of no practical disadvantage since the halogen at the 2-position is displaced in the 45 subsequent conversion of the halogenopyridine to the herbicidal pyridine compound. In addition to its usefulness as an intermediate for preparing certain of the compounds (II), 2,3- dichloro-5-trichloromethylpyridine has some biological activity as an insecticide. The invention is illustrated by the following Examples, in which all parts are by weight and all temperatures in degrees Centigrade unless otherwise specified. 50 Example 1 (a) Preparation of 2-chloro-5-trichloromethylpyridine 2-Bromo-5-methylpyridine (55 g) in dry carbon tetrachloride (600 ml) was filtered and then treated with dry hydrogen chloride to give the hydrochloride salt. The solid which separated was broken up and the 55 mixture heated to reflux. Dry chlorine was passed through the boiling mixture for 65 hours with irradiation by an ultra-violet lamp placed inside the reaction flask. The mixture was then cooled, filtered and evaporated to a pale yellow liquid which solidified on cooling. This was identified as the required chloro compound by its nuclear magnetic resonance spectrum.

60 (b) Preparation of 2-chloro-5-trifluoromethylpyridine and 2-chloro-5-difluorochloromethylpyridine 2-Chloro-5-trichloromethylpyridine (18 g) and antimony trifluoride (50 g) were heated together at 140 — 145°Cfor 1 hour. The mixture was cooled, mixed with ice and concentrated hydrochloric acid, and extracted with ether. The extracts were washed with water, dried with magnesium sulphate, and evaporated. The products from several such preparations were combined and distilled at atmospheric 65 pressure through a short column packed with Fenske rings. The product boiling at 124 — 154°C was

6 I 107 866

collected and identified as 2-chloro-5-trifluoromethylpyndine. Higner Doning Tractions were reaistmeu di a 82 to 90°C. pressure of 20 mm mercury to give 2-chloro-5-difluorochloromethylpyridine, boiling at Example 2 5 This illustrates the preparation of 2-chloro-5-trichloromethylpyridine by chlorination of 3-methylpyridine under the influence of ultra-violet light. 3-Methylpyridine (10 ml) was dissolved in dry carbon tetrachloride (300 ml). The solution was heated to reflux (about 80°) and dry chlorine gas passed through the boiling mixture for 3 hours while it was at the same time irradiated internally from a 100 watt ultra-violet lamp producing light of wavelength 185 nm. 70 Preparative thin layer chromatography (silica, chloroform/cyclohexane) on an evaporated sample of the of solution thus obtained gave three main products in total overall yield of 1 0—1 5% ; the most abundant these was identified by its nuclear magnetic resonance spectrum as the desired 2-chloro-5-trichloromethylpyridine. This was confirmed by mass spectrograph analysis of the solution obtained. The other two major products were 2-chloro-3-trichloromethylpyridine and a di(trichloromethyl)pyridine, present in 75 amount of about half, and about one-tenth, respectively of the major product.

Example 3 This Example illustrates the preparation of 2-chloro-5-trichloromethylpyridine from a salt of 3- methylpyridine. 20 3-Methylpyridine (15 g) in dry carbon tetrachloride (200 ml) was treated with dry HCI gas to give the hydrochloride. The oily mixture thus obtained was stirred and heated to reflux. Dry chlorine gas was bubbled into the refluxing mixture for 4 hours while illuminating it internally from the ultraviolet lamp used in Example 1. The reaction mixture was then cooled, and separated by decantation into solution and oily solid. The latter was purified, and shown to contain unreacted 3-methylpyridine salt. The former was 25 evaporated to an oily semi-solid, which was shown by thin-layer chromatography to have the characteristics of 2-chloro-5-trichloromethylpyridine.

Example 4 so This Example describes the preparation of 2-chloro-5-trifluoromethylpyridine by a method alternative to that of Examples 1 and 4. 2-Chloro-5-trichloromethylpyridine (30.8 g) and anhydrous hydrogen fluoride (80 g) were heated for 10 hours at 200° with stirring in an autoclave. The mixture was cooled, poured on to ice, and neutralised at 0°. The mixture was filtered and the residue and filtrate extracted with ether. The ether extracts were washed, 140—154° collected. 35 dried, and evaporated to give an oil. This was distilled and the fraction boiling at Analysis indicated that this consisted of 2-chloro-5-trifluoromethylpyridine with some 2-fluoro-5-trifluoromethylpyridine. Example 5 to (a) Preparation of 2-amino-3-bromo-5-methylpyridine 2-Amino-5-methylpyridine (108 g) in glacial acetic acid (300 ml) was heated to 90— 100°C while bromine (160 g) in acetic acid (55 ml) was slowly added with stirring. When addition was complete, the mixture was stirred and heated for a further 30 minutes and then allowed to cool overnight. The solid which separated was filtered off and mixed with ice and the mixture neutralised with concentrated ammonia, the 45 keeping the temperature at 0 to 5°C. The solid was collected, washed with water, and dried to give bromo-compound.

(b) Preparation of 3-bromo-2-chloro-5-methylpyridine The product from (a) (145 g) was dissolved in concentrated hydrochloric acid (750 ml) and water (450 with so ml) and the solution cooled to -10°C. Sodium nitrite (54 g) in cold water (450 ml) was added dropwise stirring over a period of 90 minutes while the mixture was kept at -5°C. The solution was stirred for a further 2 hours, and then basified with concentrated ammonia, keeping the temperature below 20°C. The solid which separated was washed with water, dried, dissolved in ether (1500 ml) and washed with cold sodium hydroxide solution (1M; 1 litre). The ether solution was washed twice with water (1 litre portions), 55 dried and evaporated to give the required 3-bromo-2-chloro-5-methylpyridine.

(c) Preparation of 2,3-dichloro-5-trichloromethylpyridine The product from (b) (64 g) in dry carbon tetrachloride (650 ml) was treated with dry hydrogen chloride. The precipitate was broken up and the suspension heated under reflux while dry chlorine was bubbled into 60 the mixture, with illumination from an ultra-violet light source. After 4i hours, the mixture was cooled, filtered, and the filtrate evaporated to give the required 2,3-dichioro-5-trichloromethylpyridine. The mass spectrum was consistent with the structure assigned to this compound.

(d) Preparation of 2,3-dichloro-5-trifluoromethylpyridine 65 The product from (c) (1.0 g) and antimony trifluoride (3.0 g) were heated together at 170— 180°C for 30

/ 3 107 866

minutes. The mixture was then cooled, mixed with ice and water, and extracted with ether. The ether extracts gave a brown oil containing a mixture of 2,3-dichloro-5-trifluoromethylpyridine and 3-chloro-2- fluoro-5-trifluoromethylpyridine with a minor amount of 2,3-dichloro-5-chlorodifluoromethylpyridine.

5 Example 6 2,3-Dichloro-5-trichloromethylpyridine was also prepared by an alternative route, as follows:—

(a) Preparation of 2-amino-3-chloro-5-methylpyridine 2-Amino-5-methylpyridine (10.8 g) in concentrated hydrochloric acid (100 ml) was kept at 10— 15°C w while hydrogen peroxide (30%, 21 ml) was added dropwise with stirring. When addition was complete the mixture was stirred for 1* hours without cooling, and poured on to ice (about 200 g). The mixture was brought to pH 8—9 by adding concentrated ammonia dropwise, keeping the temperature at 0°C by adding ice. The solution was extracted with chloroform (2 x 300 ml). The chloroform extracts yielded the required chloro-compound as a yellow solid. 15 (b) Preparation of 2-bromo-3-chloro-5-methylpyridine The product from paragraph (a) (5.7 g) in hydrobromic acid (48%; 50 ml) was cooled to -15°Cto -10°C and bromine (2.6 ml) was added dropwise with stirring. The temperature was then kept at -5°C to 0°C while sodium nitrite (5.53 g) in water (12 ml) was added dropwise over a period of 45 minutes. When addition was 20 complete, the mixture was stirred a further 30 minutes at 0°C and poured onto ice. The mixture was made slightly alkaline by dropwise addition of concentrated ammonia, keeping the temperature at 0°C with added ice. The mixture was extracted with ether (150 ml). The ether extract was washed with water, sodium bisulphite solution, and water, and then dried and evaporated. The residue was taken up in petroleum (b.p. 40 — 60°C) and the solution filtered and evaporated. The residue was identified as 2-bromo-3-chloro-5- 25 methyipyridine.

(c) Preparation of 2,3-dichloro-5-trichloromethylpyridine The product from paragraph (b) (2.9 g) in dry carbon tetrachloride (250 ml) was treated with dry hydrogen chloride to convert it to the hydrochloride. Chlorine was passed through the suspension which 30 was kept at 80°C and illuminated by an ultra-violet lamp inside the reaction flask. After three hours the solvent was removed, leaving a residue of 2,3-dichloro-5-trichloromethylpyridine.

Example 7 This Example illustrates the preparation of 2,3-dichloro-5-trifluoromethylpyridine by fluorination of 35 2,3-dichloro-5-trichloromethylpyridine, using a fluorinating agent alternative to that of Example 5(d). 2,3-Dichloro-5-trichloromethylpyridine (35 g) was heated with anhydrous hydrogen fluoride (100 g) in an autoclave at 200° for 10 hours with stirring. The cooled reaction mixture was poured on to ice and neutralised with sodium hydroxide at 0°. The mixture was extracted with methylene chloride (750 ml). The extracts were washed with water (500 ml), sodium carbonate solution (500 mi) and water (500 ml), dried 40 and evaporated. The remaining oil was distilled and the fraction of boiling point 77 — 83725 Torr was collected and identified as the required pyridine derivative.

Example 8 This Example further illustrates the preparation of 2,3-dichloro-5-trif!uoromethylpyridine. 45 Antimony trifluoride (61 g) was melted under a vacuum to remove moisture. The cooled material was broken up and heated to 65—70° while antimony pentachloride (6.6 g) was added dropwise with stirring. 2,3-Dichloro-5-trichloromethylpyridine (40 g) was then added dropwise to the mixture and the whole heated to 160° over 45 minutes. The mixture was cooled and steam distilled. The oil which distilled over was extracted with ether (2 x 100 ml). The ether extract was washed with tartaric acid solution then water, 50 sodium bicarbonate, and water and dried. The remaining oil was distilled. The fraction boiling at 71 — 80718 Torr was identified as the required pyridine derivative.

55 Claims

1. 2,3-Dichloro-5-trichloromethylpyridine. 2. 2,3-Dichloro-5-trifluoromethylpyridine. 3. A process for preparing a compound of formula (II)

8 1U/ BOO

herein X is chlorine or fluorine, Y is nyarogen or umumie anu u..^..„. ilorodifluoromethyl, characterised by fluorinating a compound of formula (II')

wherein Y is hydrogen or chlorine.... 2-chloro-5-tnchloromethylpyndine is fluonnated 4. A process according to claim 3 characterised in that > to qive 2-chloro-5-trifluoromethylpyridine and/or 2-fluoro-5-trifluoromethylpyndine. 2,3-dichloro-5-trichloromethylpyndine is 5. A process according to claim 3 characterised in that fluorinated to give 2,3-dichloro-5-trifluoromethylpyridine. in that the fluorinating agent is 6. A process according to any one of claims 3 to 5 characterised antimony trifluoride.... characterised that the fluorinating agent is f 7. A process according to any one of claims 3 to 5 in hydrogen fluoride.

atentanspruche

. 2,3-Dichloro-5-tnchlorometnyi-pynain. . 2,3-Dichloro-5-trifluoromethyl-pyridin. der Formel (II) . Verfahren zur Herstellung einer Verbindung

rarin X fur Chlor oder Fluor steht, Y fur wasserstorr oaer v.nior susm umu u m, @ ilorodifluoromethyl steht, dadurch gekennzeichnet, dalS man eine Verbindung der Formel (II )

worin Y fur Wasserstoff Oder (Jhlor stent, Tiuonen. 2-Chloro-5-tr.fluoromethy -pyndin 4 Verfahren nach Anspruch 3, dadurch gekennzeichnet, daG 2-Fluoro-5-trifluoromethyl-pyndin fluoriert wird, urn 2-Chloro-5-trifluoromethyl-pyridin und/oder ^'Tverfahren dalS 2,3-Dichloro-5-trichloromethyl-pyridin (0 nach Anspruch 3, dadurch gekennzeichnet, fluoriert wird, urn 2,3-Dichloro-5-trifluoromethyl-pyridin herzustellen. dalS als Fluorierungsmittel 6. Verfahren nach einem der Anspruche 3 bis 5, dadurch gekennzeichnet, Antimontrifluorid verwendet wird. dafc als Fluorierungsmitteli 7. Verfahren nach einem der Anspruche 3 bis 5, dadurch gekennzeichnet, ts Fluorwasserstoff verwendet wird. tevendications

1. La 2,3-dichloro-b-trichlorometnyipynaine. 50 2. La 2,3-dichloro-5-trifluoromethylpyridine. 3. Procede de preparation d'un compose de formule (II)

dans Iaquelle X est le chlore ou le tluor, Y est rnyarogene ou ie cniuie ei c coi um y.uu^ im„uu,Um,=u1,,u ou chlorodifluoromethyle, caracterise par la fluoration d'un compose de formule (ID

65 dans Iaquelle Y est I hydrogene ou le chlore. I 107 866

4. Procede suivant la revendication 3, caracterise en ce que de la ^-cmoro-a-tricnioromeinyipynaine e&i fluoree en donnant la 2-chloro-5-trifluoromethylpyridine et/ou la 2-fluoro-5-trifluoromethylpyridine. 5. Procede suivant la revendication 3, caracterise en ce que la 2,3-dichloro-5-trichloromethylpyridine est fluoree en donnant la 2,3-dichloro-5-trifluoromethylpyridine. ; 6. Procede suivant I'une quelconque des revendications 3 a 5, caracterise en ce que 1'agent de fluoration est le trifluorure d'antimoine. 7. Procede suivant I'une quelconque des revendications 3 a 5, caracterise en ce que I'agent de fluoration est le fluorure d'hydrogene.

'.0