PROCESS FOR PRODUCING FLUOROBENZOPHENONE DERIVATIVES

Abstract: 4-Fluorobenzophenone or 4,4′-difluorobenzophenone derivatives are produced by effecting a halogen-fluorine exchange reaction between the corresponding 4-halo­ genobenzophenone or 4,4′-dihalogenobenzophenone de­ rivative and an alkali fluoride. The reaction is carried out by heating in an organic solvent. After distilling off the solvent from the reaction product mixture, the end product is isolated by extracting with a solvent. Alternatively the end product is isolated by distillation.

Description: PROCESS FOR PRODUCING FLUOROBENZOPHENONE DERIVATIVES This invention relates to a process for the production of fluorobenzophenone derivatives and particularly, 4-fluorobenzophenone and 4,4'-difluorobenzophenone derivatives. Fluorobenzophenone derivatives, for example 4,4'difluorobenzophenone derivatives are used as materials for producing an aromatic polyketone polymer and 4-fluorobenzophenone derivatives are useful as agricultural chemicals and drugs and intermediates for dyestuffs. For producing 4,4'-difluorobenzophenone derivatives, there have been known, for example, (1) a process of reacting fluorobenzene with carbon tetrachloride in the presence of anhydrous aluminum chloride and then hydrolyzing fJ. P. Picard et al, Can. J. Research, 28B, 56 (1950); C. A., 44, 4442a (1950); Funasaka et al, Yukigoseikagaku Kyokaishi, 17, 334 (1959)1, (2) a process of effecting a Friedel-Craft's reaction between p-f luorobenzoylchloride and fluorobenzene in the presence of anhydrous aluminum chloride [R. C. Iris t al, Rev. inst. Salubridad y.enfermeded. trop., 8, 63 (1947); C. A., 42, 1921 a (1948)), (3) a process of oxidizing 2,2' bis (4-fluorophenyl)-l ,1-dichloroethylene with chromic acid (H. L. Bradlow et al, J. Am. Chem. Soc., 69, 662 (1947)) and (4) a process of treating 4,4'-diaminodiphenylmethane with sodium nitrite in anhydrous hydrogen fluoride or in a concentrated aqueous solution of hydrogen fluoride (Japanese Patent Application Kokai No. 54-132,558). Also, for producing 4-fluorobenzophenone derivatives there have been known, for example, (5) a process of effecting a Friedel-Crafts' reaction between a substituted benzoylchloride and fluorobenzene in the presence of anhydrous aluminum chloride [R. D. Dunlop et al, J. Am. Chem. Soc., 55, 1665 (1933); K. C. Joshi et al, J. Indian Chem. Soc., 40, 42 (1963); R. G. Pews et al, J. Am. Chem. Soc., 89, 2392 (1967)) and (6) a process of reacting p-fluorobenzoylchloride with an aromatic hydrocarbon in the presence of anhydrous aluminum chloride (Z. Eckstein et al, Bull. acad. polon. sci., Ser. sci., chim., geol. et geograph., 7, 803 (1959); Chem. Abstr. 54, 21005 b (1960)). However, in case of the processes (1) and (2) fluorobenzene is an expensive material and anhydrous aluminum chloride in a more than equimol relation to fluorobenzene is required. Also, the separation of the catalyst is too complicated to reuseit. Further, an apparatus made of anticorrosive material is required. In case of the process (3) fluorobenzene is used as a starting material and a large amount of glacial acetic acid is necessary. Also, since an excess of anhydrous chromic acid is used, the expenses for treating the generated waste to become non-polluting are important. In case of the process (4) the starting materials are of relatively low costs, while since a large excess of anhydrous and concentrated hydrogen fluoride is used, the recovery of hydrogen fluoride is necessary. Further, for the production an apparatus made of specific materials such as a reaction and recovery vessel of anti-corrosive materials is required and also, the toxicity of hydrogen fluoride should be taken into consideration. In case of the processes (5) and (6) fluorobenzene and p-fluorobenzoylchloride are industrially expensive and anhydrous aluminum chloride in more than the equimolar amount is necessary. The separation of the catalyst is too complicated to reuse it and also, the load for treating the generated waste fluid is heavy. Therefore, the application of these processes in a commercial scale is accompanied with various difficulties. Regarding the described prior art it is therefore an object of this invention to provide a process for producing fluorobenzophenone derivatives conveniently in a commercial scale starting from the corresponding halogenobenzophenone derivatives. In accordance with this invention there is provided a process for the production of fluorobenzophenone derivatives which comprises effecting a halogen-tluorine exchange reaction between a 4-halogenobenzophenone derivative of Formula I. EMI4.1 wherein X is a chlorine, bromine or iodine atom, R is hydrogen, an alkyl group, an aralkyl group, a cycloalkyl group, an aryl group, an alkoxy group, an aryloxy group, an alkylthio group, a carboalkoxy group, an acetyl group, a trifluoromethyl group, a nitro group or a chlorine, bromine or iodine atom and n is an integer of 1-5 and when n is 2 or more, R may be the same or different, and an alkali fluoride. In the following the invention is described in more detail. According to this invention, the corresponding 4-fluorobenzophenone derivatives are produced with a high yield by heating the 4-halogenobenzophenone derivative of Formula I and an alkali fluoride in an organic solvent. After distilling off the solvent from the reaction product mixture, the end product is isolated easily by extracting with a solvent. Alternatively, the end product is isolated by distillation. Therefore the process of this invention is quite advantageous industrially. The 4-halogenobenzophenone derivatives of Formula I which may be used in this invention'are, for example, 4-halogenobenzophenone, 4-nalogeno-3' -methylbenzophenone, 4-halogeno-4'-methylbenzophenone, 4-halogeno-4'-ethylbenzophenone, 4-halogeno-4 '-n-butylbenzophenone, 4-halogeno 2' ,4 '-dimethylbenzophenone, 4-halogeno-2' ,5 '-dirnethyl- benzophenone, 4-halogeno-4'-phenylbenzophenone, 4-halogeno4'-methoxybenzophenone, 4-halogeno-4 '-ethoxybenzophenone, 4-halogeno-4'-phenoxybenzophenone, 4-halogeno-4'-methylthiobenzophenone, 4-halogeno-3 '-carbomethoxybenzophenone, 4-halogeno-3'-acetylbenzophenone, 4-halogeno-3'-trifluoromethylbenzophenone, 4-halogeno-3'-nitrobenzophenone, 4-halogeno-4'-nitrobenzophenone, 2-chloro-4 '-halogenobenzophenone, 2-bromo-4 '-nalogenobenzophenone, 3-chloro4'-halogenobenzophenone, 4-halogeno-3',5'-dichlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-dibromobenzophenone and 4,4'-diiodobenzophenone. These 4-halogenbenzophenone derivatives of Formula I may be prepared by effecting a Friedel-Craft's reaction between p-chloro-, p-bromo- or p-iodo-benzoyl chloride and an aromatic hydrocarbon which are both readily available in a commercial scale or between a substituted benzoylchloride and chlorobenzene, bromobenzene or iodobenzene in the presence of an anhydrous ferric chloride catalyst. The alkali fluorides which may be used in this invention are, for example, cesium fluoride, rubidium fluoride, potassium fluoride, sodium fluoride and lithium fluoride. Taking into consideration the yield of end product cesium fluoride, rubidium fluoride and potassium fluoride are preferred. These may be used in mixture of two or more. The amount of the alkali fluoride for attaining the halogenfluorine exchange reaction is not particularly limited, though a small excess over the stoichiometrical amount is preferred. The amount may be decided according to the yield and economy. The organic solvent used in this invention is, for example, a sulphur-containing polar solvent e.g. dimethyl sulfoxide, dimethyl sulfone, diphenyl sulfoxide, diphenyl sulfone, tetrahydrothiophene-1,1-ciioxide (sulfolane) and a nitrogen-containing polar solvent e.g. N,N-dimethylformamide, N,N-dimethylacctamide, N-methylpyrrolidone, 1 ,3-dimethyl-2- imidazolidinone (DM1) and hexamethylphosphoric acid triamide (HMPA) and other non-proton polar solvents. The reaction temperature is, in general, between 1000 and 3500C. The progress of the reaction is traced by gas chromatography or thin layer chromatography and the reaction is completed when most of the starting materials have disappeared. The process of this invention is carried out by heating the 4-halogenobenzophenone of Formula I and alkali fluoride in the organic solvent under stirring. In this case, an inter layer moving catalyst such as a large ring polyether (crown ether), quaternary ammonium salts and quaternary phosphonium salts may be added to stabilize an alkali metal cation. According to a preferred embodiment of this invention, a small amount of benzene is added to the organic solvent containing the 4-halogenobenzophenone of Formula I and alkali fluoride and heated. Water in the reaction system is removed in the form of an azeotropic mixture with benzene and thereafter, heating is continued at indicated temperatures under stirring, which is effected, preferably under nitrogen atmosphere to prevent the solvent from decomposing. After the indicated reaction time, the resulting products are cooled and the final compound is extracted by an organic solvent. Examples of the solvent for extraction include alcohols such as methanol, ethanol and isopropanol, halogenated hydrocarbons such as 1,2-dichloroethane, chloroform and carbon tetrachloride and benzenes such as benzene and toluene. Alternatively, after completion of the reaction the solvent is distilled off under reduced pressure and then, the residues are subjected to extraction with the above extraction solvent to isolate the end product. Also, the end product may be isolated directly during the distillation under reduced pressure. If necessary, a product of high purity can be obtained by a conventional solvent recrystallization. This invention will be illustrated by the following non-limitative examples. Example 1 To a mixture of 10.1 g (0.04 mols) of 4,4'dichlorobenzophenone, 9,3 g (0.16 mols) of potassium fluoride and 20 g of dimethyl sulfone were added 5 ml of benzene. Water in the reaction system was removed together with benzene by azeotropic distillation. The reaction was carried our under a nitrogen atmosphere at temperatures of 230-2400C while stirring for 45 hours. After cooling, the reaction product was extracted twice with 15 ml of isopropanol under heating. When the joined extracts were cooled, 7.0 g of 4,4'-difluorobenzophenone was obtained. Yield 80%, Melting point 106-1070C Pure product was obtained by recrystallisation with a methanol/water (80/20) mixture. Melting point 106-1 07 OC. Elementary Analysis C(e) l3lE) F(%) Calculated 71.5 3.70 17.4 Found 71.2 3.50 17.2 Example 2 lo a mixture of 10.1 g (0.04mols) of 4,4'dichlorobenzophenone, 9.3 g (0.16 mols) of potassium fluoride and 20 g of dimethyl sulfone were added 5 ml of benzene and the water in the reaction system was removed together with benzene by azeotropic distillation. 0.5 g of Dibenzo-18crown-6-ether were added thereto and the reaction was carried out under a nitrogen atmosphere at temperatures of 230-240"C while stirring for 30 hours. The post-treatment was effected in the same manner as in Example 1. 7.0 g of 4,4'-difluorobenzophenone were obtained. Yield 80 %, M.P. 106-1070C Example 3 Using 13.b g (0.04 mols) of 4,4'-dibromobenzophenone, 9.3 g (0.16 mols) of potassium fluoride and 20 g of dimethyl sulfone, 6.8 g of 4,4l-uifluorobenzophenone were obtained in the same procedure as in Example 1. ' Yield 78%, M.P. 106-1070C Example 4 To a mixture of 10.1 g (O.u4 mols) of 4,4'dichlorobenzophenone, 7.0 g (0. i2 mols) of potassium fluoride and 25 g of sulfolane 5 ml of benzene were added and the water in the reaction system was removed together with benzene by azeotropic distillation. The reaction was carried out under a nitroqen atmosphere at temperatures of 273-2770C while stirring for ten hours. After cooling the sulfblane was distilled off under reduced pressure. The residues were extracted twice with 20 ml of isopropanol under heating. When the joined extracts were cooled, 5.7 g of 4,4'-difluorobenzophenone were obtained. Yield 65%, M.P. 106-1070C Example 5 To a mixture of 10.1 g 40. 04 mols) of 4,4'dichlorobenzophenone, 15.2 g (0.1 mol) of cesium fluoride and 25 g of sulfolane 5 ml of benzene were added and the water in the reaction system was removed together with benzene by azeotropic distillation. The reaction was carried out under a nitrogen atmosphere at temperatures of 200-2100C while stirring for ten hours. After cooling the post-treatment was effected in the same manner as in Example 4 and thus, 7.4 g of 4,4'difluorobenzophenone were obtained. Yield 85%, M.P. 106-1070C Example 6 To a mixture of 20.2 g (0.08 mols) of 4,4'dichlorobenzophenone, 30.4 g (0.2 mols) of cesium fluoride and 50 g of N-methylpyrrolidone 10 ml of benzene were added and the water in the reaction system was removed together with benzene by azeotropic distillation. The reaction was carried out under nitrogen atmosphere at temperatures of 200-202"C while stirring for 20 hours. After cooling the N-methylpyrrolidone was distilled off under reduced pressure. 12 g of 4,4'-Difluorobenzophenone were obtained by distillation under reduced pressure. Yield 70%, M.P. 105-1060C Boiling Point 150-1550C/12 mmHg. Pure product was obtained by recrystallization with isopropanol. M.P. 106-1070C Example 7 To a mixture of 10.1 g (0.04 mols) of 2,4'dichlorobenzophenone, 4.6 g (0.08 mols) of potassium fluoride and 20 g of dimethyl sulfone 5 ml of benzene were added and the water in the reaction system was removed together with benzene by azeotropic distillation. The reaction was carried out under a nitrogen atmosphere at temperatures of 230-240"C while stirring for 11 hours. After cooling the reaction product was extracted under heating twice with 20 ml of isopropanol. The extracts together were cooled and thus, 7.5 g of 2-chloro-4'fluorobenzophenone were obtained. Yield 80t, M.P. 60-610C Pure product was obtained by recrystallization with isopropanol. M.P. 60-610C Example 8-13 Using 0.04 mols-of 4-chlorobenzophenone derivatives, the reaction was carried out in the same procedure as in Example 7 to obtain the corresponding 4-fluorobenzophenone derivatives. The results obtained are set forth in Table 1. Table 1 EMI12.1 <tb> Ex. <SEP> 4-Fluorobenzophenone <SEP> Yield <SEP> M.P. <tb> No. <SEP> derivatives <SEP> (%) <SEP> <SEP> ( C) <SEP> <tb> <SEP> 8 <SEP> 4-Fluorobenzophenone <SEP> 86 <SEP> 49-50 <tb> <SEP> 9 <SEP> 4-Fluoro-3'-methylbenzophenone <SEP> 81 <SEP> 97-98 <tb> 10 <SEP> 4-Fluoro-4'-n-butylbenzophenone <SEP> 78 <SEP> 75-76 <tb> 11 <SEP> 4-Fluoro-4'-phenylbenzophenone <SEP> 80 <SEP> 148-l49 <SEP> <tb> 12 <SEP> 4-Fluoro-4'-ethoxybenzophenone <SEP> 72 <SEP> 87-88 <tb> 13 <SEP> i <SEP> 4-Fluoro-3'-trifluoromethyl- <SEP> 82 <SEP> 100-101 <tb> <SEP> benzophenone <tb> Example 14 To a mixture of 12.2 g (0.05 mols) of 4-chloro2 2,,4'-dimethylbenzophenone, 12.1 g (0.08 mols) of cesium fluoride and 20 g of N-methylpyrrolidone were added 5 ml of benzene and the water in the reaction system was removed together with ben zene by azeotropic distillation. The reaction was carried out under nitrogen atmosphere by heating under reflux while stirring for 15 hours. After cooling, the reaction product obtained was poured into 100 ml of water and then, extracted with 50 ml of diethyl ether and further with 50 ml of ether. The extracts together were dried and distilled and thus, 8.9 g of 4-fluoro-2',4'-dimethylbenzophenone were obtained. Yield : 78 %, B.P. 151-152 C/10 mmHg Example 15 To a mixture of 14.4 g (0.05 mols) of 4-bromo2',5'-dimethylbenzophenone, 5.5 g (0.095 mols) of potassium fluoride, 0.06 g (0.005 mols) of cesium fluoride and 20 g of sulfolane were added 5ml of benzene and the water in the reaction system was removed together with benzene by azeotropic distillation. The reaction was carried out under a nitrogen atmosphere at temperatures of 245-2500C while stirring for 15 hours. After cooling, the reaction products were poured into 100 ml of water and then, extracted with 50 ml of diethyl ether and further with 50 ml of ether. The extracts together were dried and distilled and thus, 7.8 g of 4-fluoro-2',5'dimethylbenzophenone were obtained. Yield 69%, B.P. 164-1660C/10 mmHg

Claims: CLAIMS 1. A process for producing fluorobenzophenone derivatives which comprises effecting a halogen-tluorine exchange reaction between 4-halogenobenzophenone derivatives of Formula I, EMI14.1 wherein X is chlorine, bromine or iodine atom, R is hydrogen, an alkyl group, an aralkyl group, a cycloalkyl group, an aryl group, an alkoxy group, an aryloxy group, an alkylthio group, a carboalkoxy group, an acetyl group, a trifluoromethyl group, a nitro group or a chlorine, bromine or iodine atom, n is an integer of 1-5 and when n is 2 or more, R is the same or different,and an alkali fluoride. 2. The process of claim 1 wherein said halogenfluorine exchanging reaction is carried out in an organic solvent at temperatures of 100-3500C. 3. The process of claim 1 wherein said alkali fluoride is at least one member selected from lithium fluoride, potassium fluoride, sodium fluoride, rubidium fluoride and cesium fluoride. 4. The process of claim 1 wherein said halogenfluorine cxchanging reaction is carried out in the presence of an interlayer moving catalyst.

Inventors: SUGIMOTO, KENICHI, TANABE, YOSHIMITSU, YAMAGUCHI, AKIHIRO, YAMAGUCHI, KEIZABURO MITSUI TOATSU CHEMICALS'
Applicants: MITSUI TOATSU CHEMICALS, INCORPORATED
Application year: 1982
Main classification: C07C49
IPC codes: C07C51, C07C323, C07C205, C07C49, C07C201, C07C45, C07C69, C07C67, C07C313