CH615902A5 - Process for the preparation of substituted anilines - Google Patents

Abstract

The compounds of formula (I) <IMAGE> in which one of the substituents X or Y represents a pentafluoroethyl group, the other being a hydrogen atom, are used as raw materials for the preparation of dyes. The said compounds are produced by condensation, in the presence of copper powder, in a dipolar aprotic solvent, of pentafluoroethyl iodide with an ortho- or para-halonitrobenzene. The intermediate product, that is to say the ortho- or para-pentafluoroethylnitrobenzene, is then reduced to the compound of formula (I). The ortho- or para-pentafluoroethylaniline thus obtained is used in conversions to nitro compounds by acetylation, nitration and hydrolysis or ethanolysis, to bromo compounds by bromination and finally to cyano compounds by reaction with cuprous cyanide.

Description

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1. Process for obtaining o- or p-pentafluoroethyl-anilines of formula (I)

(I)

in which one of the substituents X or Y represents a pentafluorethyl group, the other being a hydrogen atom, characterized in that the iodide is condensed, in the presence of powdered copper, in an aprotic dipolar solvent of pentafluoroethyl with an o- or p-halonitrobenzene, and in that the o- or p-pentafluoroethylnitrobenzene thus obtained is reduced in order to obtain the compounds of formula (I).

2. Process for obtaining 4-nitro-2-pentafluoroethyl-aniline or 2-nitro-4-pentafluoroethyl-aniline of formula (II)

(II)

in which one of the substituents X or Y 'represents a pentafluoroethyl group and the other being the nitro group, characterized in that the o- or p-pentafluoroethylaniline of formula (I) is prepared by the process according to claim 1 and then it is transformed by acetylation, nitration and hydrolysis or ethanolysis, to obtain the compounds of formula (II).

3. Process for obtaining 6-bromo-4-nitro-2-pentafluoroethyl-aniline or 6-bromo-2-nitro-4-pentafluoroethyl-aniline of formula (III)

(III)

NH,

in which the specifications for X and Y 'are the same as in formula (II) and in which Z represents bromine, characterized in that the 4-nitro-pentafluoroethyl-2 aniline or the 2-nitro-pentafluoroethyl-4 is prepared aniline of formula (II) by the process according to claim 2 and then it is transformed by bromination to obtain the compounds of formula (III).

4. Method according to claim 1, characterized in that the condensation is carried out at a temperature of 100 to 130 ° C.

5. Method according to claim 1, characterized in that the aprotic dipolar solvent used is dimethylformamide.

6. Method according to claim 1, characterized in that the halonitrobenzene used is parabromonitrobenzene or orthochloronitrobenzene.

7. Compounds of formula (I), obtained by means of the process according to claim 1.

8. Compounds of formula (II), obtained by the process according to claim 2.

9. Compounds of formula (III), obtained by means of the process according to claim 3.

It is known (see US patents Nos. 3058979 and 3281426, as well as WA Sheppard, "JACS", 87, (1965), 2410 to 2420, and VCR Me Loughlin, J. Thrower, "Tetrahedron", 25 (1969), 5921 to 5940) a certain number of arylamines bearing on the aromatic nucleus, in the meta position relative to the amino group, a perfluoroalkyl group. Such arylamines are prepared in particular by nitration of a perfluoroalkylbenzene and subsequent reduction of the nitro derivative obtained.

5 It is also known (see French patent N ° 1538366 requested on 5/30/67 and issued on 7/29/68, as well as PL Coe, NE Milner, "Journal of Fluorine Chemistry", 2 (1972/73 ), 167 to 172; Kobayashi et al., "Chem. Pharm. Bull.", 18 (1970), 2334 to 2339; VCR Me Loughlin, J. Thrower, reference already cited) to prepare perfluoroalkylnitrobenzenes carrying a group CF3, C3F7 or C7F15 in the ortho or para position relative to the nitro group, by the hot action of a perfluoroalkyl iodide on an o- or p-halogenonitrobenzene, in the presence of copper, in an aprotic dipolar solvent. The yields of perfluoroalkylnitrobenzene obtained vary widely with the nature of the halogen of the aromatic compound and are very low (20% at most) in the case where this halogen is a chlorine atom.

However, the only perfluoroalkylarylamines having a perfluoroalkyl group in the ortho or para position relative to the amino group, described so far are the o- and p-trifluoromethyl-anilines (see RG Jones, "JACS", 69 (1947), 2346 ).

Now, it is advantageous, for the preparation of coloring matters, to have ortho- and paraperfluoroalkylarylamines por-25 a perfluoroalkyl group other than CF3, in particular a pentafluoroethyl group C2F5.

The methods according to the invention are defined in claims 1, 2 and 3.

The pentafluoroethylarylamines prepared according to the invention can be represented by the general formula:

x R

sT-'C / 1 (I)

Y - #> - N

35 v, "2

in which one of the substituents X or Y represents a pentafluoroethyl group, the other being a hydrogen atom, a cyano, nitro or sulfonic group, Z represents a hydrogen atom, 40 of chlorine or bromine or a group nitro or cyano, Ri represents a hydrogen atom, R2 represents a hydrogen atom, an alkyl or acyl group.

The condensation of pentafluoroethyl iodide with an o- or p-halonitrobenzene is carried out hot, in the presence of 45 powdered copper, in an aprotic dipolar solvent. The reaction temperature is preferably in the range 100-130 ° C. The powdered copper used is so-called precipitated copper prepared by reduction of copper sulphate by zinc according to the Brewster-Groening technique (“Organic Synthesis”, vol. II 50 (1943), 446). As aprotic dipolar solvents which can be used, mention may in particular be made of dimethylsulfoxide, hexamethylphos-phorotriamide and especially dimethylformamide (DMF).

The ortho- or parahalononitrobenzene used in the condensation reaction can be a chlorinated, brominated or iodinated derivative. It has been found in particular that it is possible, starting from a chlorinated or brominated derivative, to prepare o- or p-pentafluoroethylnitrobenzene with excellent yields, which is unexpected.

The o- and p-pentafluoroethylnitrobenzenes formed in the condensation reaction, which are new products, can be separated from the reaction medium by extraction with ether or, preferably, entrainment with steam, and then isolated with water. 'pure state by distillation under reduced pressure. However, the isolation of pentafluoroethylnitrobenzene is not necessarily necessary for the rest of the operations, the crude product separated by entrainment with 65 steam can be subjected directly to the reduction treatment.

The reduction of o- or p-pentafluoroethylnitrobenzene to o- or p-pentafluoroethylaniline can be carried out, for example, by

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catalytic reduction, using hydrogen in the presence of palladium carbon. The o- or p-pentafluoroethylanilines are isolated in the pure state and by entrainment with water vapor in an acid medium and / or distillation under reduced pressure.

The nitro, sulphonated, chlorinated, brominated, cyanated, N-alkylated and N-acylated derivatives of o- and p-pentafluoroethylanilines are obtained from the latter according to methods known per se. They are isolated by precipitation or distillation.

The following examples, in which the parts are by weight, unless otherwise stated, illustrate the invention.

Example 1:

Preparation of parapentafluoroethylaniline.

100 parts of powdered copper, 101 parts of p-bromo-nitrobenzene dissolved in 300 parts of technical DMF and 160 parts of carbon dioxide are successively introduced into a stainless steel reactor fitted with stirring, heating and cooling systems. pentafluoroethyl iodide previously cooled to -78 ° C. The reactor is closed quickly, stirring and heating are started and the mixture is heated at 130 ° C for 28 h. After cooling, the contents of the reactor are poured into a flask, the reactor is washed thoroughly with water and the washing waters are joined to the contents of the flask. The contents of the flask are subjected to steam entrainment. 114 parts of an orange oil more dense than water are thus obtained. By distillation of this oil under reduced pressure, 108 parts of parapentafluoroethylnitrobenzene are isolated, in the form of a fraction passing at 40 ° C under 0.5 mm Hg, whose refractive index at 20 ° C is njj ° = 1.445 .

Analysis for C8H4F5NO2:

Calculated: C 39.84 H 1.67 N5.81 F 39.40%

Found: C 39.89 H 1.92 N5.74 F 39.19%

The yield of p-pentafluoroethylnitrobenzene, calculated relative to the p-bromonitrobenzene introduced, is 90%.

100 parts of p-pentafluoroethylnitrobenzene prepared as indicated above are introduced into a stainless steel reactor, 100 parts by volume of methanol and 2 parts of palladium on carbon containing 5% palladium. The mixture is stirred and heated to 100 ° C., under a hydrogen pressure of 30 atmospheres, until there is no longer any absorption of hydrogen. After cooling, the contents of the reactor are filtered and the solution obtained is distilled under reduced pressure. Is thus isolated, in the form of a fraction passing at 46 ° C under 1 mm Hg, 78 parts of parapentafluoroethylaniline, with a refractive index n ^ ° = 1.452.

Analysis as C8H7CIF5N hydrochloride:

Calculated: C 38.80 H 2.85 N5.66 F 38.37%

Found: C 38.61 H 2.98 N5.50 F 38.24%

The yield of p-pentafluoroethylaniline, calculated relative to p-pentafluoroethylnitrobenzene, is 89%.

Example 2:

Preparation of orthopentafluoroethylaniline.

For the preparation of o-pentafluoroethylnitrobenzene, the procedure is as in Example 1, except that the 101 parts of p-bromonitrobenzene are replaced by 80 parts of o-chloronitrobenzene and the reaction mixture is heated to 100 ° C. for 72 h. By steam stripping, 123 parts of a yellow oil are separated containing 90% by weight of o-pentafluoroethylnitrobenzene (percentage determined by chromatography), which corresponds to a yield of o-pentafluoroethylnitrobenzene, calculated relative to o-chloronitrobenzene introduced, equal to 91%.

By distillation under reduced pressure of the preceding yellow oil, it is possible to isolate, in the form of a fraction passing at 48 ° C.

at 0.4 mm Hg, pure orthopentafluoroethylnitrobenzene. This compound has a refractive index n ^ ° = 1.441.

Analysis for C8H4F5NO2:

Calculated: C 39.84 H 1.67 N5.81%

Found: C 39.93 H 1.76 N6.05%

123 parts of the yellow oil previously obtained, 100 parts by volume of methanol and 2 parts of palladium on carbon containing 5% palladium are introduced into a stainless steel reactor. The mixture is stirred and heated to 100 ° C., under a hydrogen pressure of 30 atmospheres, until there is no longer any absorption of hydrogen. After cooling, the contents of the reactor are filtered, the methanol is removed by distillation and the oily residue obtained is poured into 500 parts by volume of a normal sulfuric acid solution, then subjected to a steam entrainment. 83 parts of orthopentafluoroethylaniline are thus isolated, which corresponds to a yield, calculated with respect to o-pentafluoroethylnitrobenzene, of 85%.

Analysis for CsHöFsN:

Calculated: C 45.50 H 2.87 N 6.63 F 45.00%

Found: C 45.78 H 2.77 N 6.54 F 45.15%

O-pentafluoroethylaniline has a boiling point of 73 ° C under 22 mm Hg and a refractive index n, 30 = 1.450.

Example 3:

Preparation of paraacetylaminopentafluoroethylbenzene.

A mixture of 40 parts of p-pentafluoroethylaniline, 40 parts by volume of acetic acid and 40 parts by volume of acetic anhydride is heated at reflux for 30 min. The hot mixture is poured slowly into 11 of water, the precipitate obtained is filtered, drained and dried in the oven at 50 ° C. 46.5 parts of paraacethylaminopentafluoroethylbenzene are thus obtained. This product, recrystallized from ethanol, has a melting point of 130 ° C.

Analysis for CioHgFsNO:

Calculated: C 47.44 H 3.18 N5.53%

Found: C 47.57 H 3.21 N5.31%

Example 4:

Preparation of orthoacetylaminopentafluoroethylbenzene. The procedure is as in Example 3, initially with 40 parts of o-pentafluoroethylaniline instead of 40 parts of p-pentafluoroethylaniline. 44 parts of orthoacetylaminopenta-fluoroethylbenzene are obtained. This product, recrystallized from ethanol, has a melting point of 112 ° C.

Analysis for C10H3F5NO:

Calculated: C 47.44 H 3.18 N5.53%

Found: C 47.55 H 3.32 N5.51%

Example 5:

Preparation of 2-nitro-pentafluoroethyl-4 aniline.

In 60 parts by volume of concentrated sulfuric acid, 25.3 parts of p-acetylaminopentafluoroethylbenzene are dissolved. The solution is cooled, in an ice-salt bath, to a temperature below 0 ° C. and 6.5 parts of fuming nitric acid (density 1.52) are added dropwise while maintaining the temperature below 0 ° C. The mixture is then stirred at this same temperature for 1 h, then 1 h at room temperature. It is then poured over 500 parts of ice. The precipitate obtained is filtered, washed with water until neutral, drained and dried in an oven at 50 ° C.

The product obtained is dissolved in 55 parts by volume of ethanol. The solution is brought to reflux and 32 parts by volume of concentrated hydrochloric acid are added in portions. The

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mixture is heated at reflux for 1 h, then diluted with 150 parts of water. The volatile products (ethanol and ethyl acetate) are removed by distillation and the precipitate obtained is filtered, washed with water, drained and dried in an oven at 50 ° C. This gives 23.6 parts of nitro- 2 pentafluoroethyl-4 aniline. This product, recrystallized from cyclohexane, has a melting point of 90 ° C.

Analysis for C8H5F5N2O2:

Calculated: C 37.51 H 1.97 N 10.94 F 37.09%

Found: C 37.29 H 1.96 N 10.85 F 37.10%

Example 6:

Preparation of 4-nitro-2-pentafluoroethyl aniline.

The procedure is as in Example 5, initially with 25.3 parts of o-acetylaminopentafluoroethylbenzene instead of 25.3 parts of p-acetylaminopentafluoroethylbenzene. 23 parts of 4-nitro-pentafluoroethyl-2 aniline are obtained. This product, recrystallized from cyclohexane, has a melting point of 84 ° C.

Analysis for C8H5F5N2O2:

Calculated: C 37.51 H 1.97 N 10.94%

Found: C 37.81 H 1.95 N 10.71%

Example 7:

Preparation of 6-bromo-4-nitro-pentafluoroethyl-2 aniline.

25.6 parts of 4-nitro-2-pentafluoroethyl aniline are dissolved in 100 parts by volume of acetic acid. 16.8 parts of bromine dissolved in 100 parts by volume of acetic acid are added dropwise. The mixture is heated at reflux for 4 h then, after cooling, poured into 11 of water. The precipitate obtained is filtered, washed with 250 parts by volume of a 10% sodium bisulfite solution, then with water, drained and dried in an oven at 50 ° C. This gives 30 parts of bromo- 6 nitro-4 pentafluoroethyl-2 aniline. This product, recrystallized from ethanol, has a melting point of 133 ° C.

Analysis for CsH4BrFsN202:

Calculated: C 28.88 H 1.25 N8.37 Br 23.86%

Found: C 28.68 H 1.20 N8.06 Br 23.34%

Example 8:

Preparation of 2,6-dinitro-pentafluoroethyl-4 aniline. 10 parts of 2-nitro-pentafluoroethyl-4 aniline are dissolved in 45 parts by volume of nitric acid (density 1.42). The mixture is heated at 35 ° C for 1 h, then poured onto 300 parts of ice. The precipitate obtained is filtered, washed with water, drained and air dried. 10.8 parts of 2-nitro-4-pentafluoroethylphenylnitramine are thus obtained, which melts at 58-59 ° C.

This product is added in portions to 100 parts by volume of concentrated sulfuric acid cooled, in an ice-salt bath, at a temperature below 0 ° C. The mixture is stirred for 1 h, then poured onto ice. The precipitate obtained is filtered, washed with water, drained and dried in an oven at 50 ° C. This gives 10 parts of 2,6-dinitro-4-pentafluoroethyl-aniline.

Analysis for C8H4F5N3O4:

Calculated: C 31.90 H 1.34 N 13.95 F 31.55%

Found: C 31.75 H 1.23 N 13.58 F 31.23%

This product, recrystallized from ethanol, has a melting point of 105 ° C.

Example 9:

Preparation of dinitro-4,6 pentafluoroethyl-2 aniline.

The procedure is as in Example 8, starting with 10 parts of 4-nitro-pentafluoroethyl-2 aniline instead of 10 parts of 2-nitro-pentafluoroethyl-4 aniline. 8.4 parts of 4,6-dinitro-pentafluoroethyl-2 aniline are obtained. This product, recrystallized from ethanol, has a melting point of 132 ° C.

Analysis for C8H4F5N3O4:

Calculated: C 31.90 H 1.34 N 13.95 F 31.55%

Found: C 32.15 H 1.27 N 13.42 F 31.04%

Example 10:

Preparation of 4-sulfo-pentafluoroethyl-2 aniline.

21.1 parts of orthopentafluoroethylaniline are dissolved in 200 parts by volume of sym-tetrachloroethane. The solution is cooled, in an ice-salt bath, to a temperature below 0 ° C., then 12 parts of chlorosulfuric acid SO3HCI dissolved in 50 parts by volume of tetrachloroethane are added dropwise, while maintaining the temperature in the vicinity 0 ° C. The mixture is then heated at 125 ° C for 3 h. After cooling, the precipitate obtained is filtered, washed with hexane, drained and dried in an oven at 50 ° C. This gives 29 parts of 4-sulfo-2-pentafluoroethyl-aniline. This product, recrystallized from water, melts with decomposition at 250 ° C.

Analysis for C8H6F5NO3S:

Calculated: C 33.00 H 2.08 N4.81 F 32.63%

Found: C 32.77 H 2.25 N 4.70 F 32.59%

Example 11:

Preparation of cyano-6 nitro-4 pentafluoroethyl-2 aniline.

A mixture of 33.5 parts of 6-bromo-4 nitro-2-pentafluoroethyl-aniline and 13.4 parts of cuprous cyanide in 80 parts by volume of dimethylformamide is heated at 150 ° C for 3 h. The hot mixture is poured with stirring into a solution of 32 parts of ferric chloride in 14 parts by volume of concentrated hydrochloric acid and 100 parts of water. After 30 minutes of stirring, 200 parts of water are added. The precipitate obtained is filtered, washed with water until neutral and carefully wrung. The precipitate is then taken up on the filter with acetone. The acetone solution is evaporated and the solid obtained is recrystallized from alcohol. 16.8 parts of 6-cyano-4-nitro-pentafluoroethyl-2 aniline are thus obtained, the melting point of which is 158 ° C.

Analysis for C9H4F5N3O2:

Calculated: C 38.45 H 1.43 N 14.95 F 33.79%

Found: C 38.16 H 1.40 N 14.48 F 34.10%

The bromo-6 nitro-2 pentafluoroethyl-4 aniline and the cyano-6 nitro-2 pentafluoroethyl-4 aniline can be prepared according to the methods described in Examples 7 and 11, initially replacing the nitro-4 pentafluoroethyl-2 aniline by nitro-2 pentafluoroethyl-4 aniline and bromo-6 nitro-4 pentafluoroethyl-2 aniline by bromo-6 nitro-2 pentafluoroethyl-4 aniline.

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