DE2438506A1 - Nuclear substd. N,N-dimethyl-anilines prepn. - by reacting substd. nitrobenzenes with formaldehyde under reducing conditions - Google Patents

Abstract

N,N-Dimethylaniline of formula (I): (where R1,R2 and R3 are halogen, an aromatic residue, an aliphatic residue, -OR4, -COR4 or -NHCOR4 (R4 being an aliphatic residue), and R2 and R3 can also be H or -COOR5 (R5 being an aliphatic or aromatic residue), or adjacent residues R3 or R1 and an adjacent residue R3 can be linked so as to form a fused heterocyclic residue), e.g. p-dimethylamino-chlorobenzene or 3,4-dichloro-N,N-dimethylaniline, are prepd. by reacting nitrobenzenes of formula (II) with formaldehyde and hydrogen in the presence of a hydrogenation catalyst contg. one or more metals of atomic number 24-29 and of a weak organic acid at 35-250 degrees C under a pressure of at least 40 atmos. (I) are intermediate for dyes (esp. crystal violet dyes and reactive dyestuffs) and pesticides. They can also be used as stabilizers for unsatd. polyester resins (cf. BE 640930), and the halo-substd. dimethylanilines can be used as photoinitiators in photosensitive compsns. (cf. US 3515552 and 3539346) for the prodn. of galvanic metal coatings (cf. DT 934508) and in the prodn. of polymethylmethacrylate mouldings (DL17190) Provides simple and economical process giving (I) in better yields, purity and space-time yields than known processes. The process does not require expensive catalysts, and is suitable for large-scale use. Corrosion problems are avoided.

Description

Process for the preparation of dimethylaminobenzene compounds additive to patent application P 23 29 553.6.

The invention relates to a process for the preparation of dimethylaminobenzene compounds by reacting nitrobenzene compounds with formaldehyde and hydrogen in the presence a hydrogenation catalyst containing metals of atomic number 24 to 29 and a weak acid at a temperature of 35 to 1590C and a pressure of at least 40 at.

It is from the Australian Journal of Chemistry, Volume 23 (1970), page 204 in connection with Journal of the American Chemical Society, Volume 73 (1951), Page 864 known that m-dimethylaminobenzoic acid methyl ester by reductive Methylation of methyl m-nitrobenzoate with hydrogen and formaldehyde in ethyl alcohol in the presence of hydrochloric acid and a pre-reduced Adams catalyst at 5 ° C and a pressure of 45 lb. The article in the American Journal points out that reductive methylation is rarely used to produce it tertiary, aromatic amines is used, as a condensation of the starting materials occurs easily, and only recommends the above-mentioned procedure. The Australian Journal does not report any yield of ester produced in this way. Leads if the process is carried out on an industrial scale, the yield is poor of end product. As the purpose of the 3-dimethylaminobenzoic acid methyl ester or the 3-dimethylaminobenzoic acid requires high purity, is the separation the end product is expensive and therefore the process is not economically satisfactory0 The German imperial patent 716 668 teaches that also for reductive methylation special conditions must be observed for aminobenzoic acid derivatives. Though can be used with other catalysts, e.g. nickel on kieselguhr from Additional catalysts such as piperidine, secondary amines obtained, e.g. from ethyl p-aminobenzoate with isobutyraldehyde ethyl isobutylaminobenzoate. For making tertiary Amines, e.g. of p-N-dimethylaminobenzamide or of N-dimethylaminobenzoic acid ethyl ester from the corresponding primary amines by reductive methylation, such as Examples 12 and 15 show platinum catalysts in the presence of hydrochloric acid at 200C and at 3.5 atmospheric pressure. The yields of the end product are not given.

Also palladium on activated carbon in the presence of acetic acid or in Ethanol solution, optionally together with sodium acetate, is used as a catalyst at room temperature under normal pressure for the reductive methylation of nitrobenzoic acids (J. Chem. Soc. 1950, pages 1 342 ff).

In Freifelder, Practical Catalytic Hydrogenation (Wiley, N.Y ,, (1971), Pages 346 ff.) It is shown that depending on the starting material and the selected substituents specific catalysts and reaction conditions must be chosen. Special in the case of the reductive methylation of 4-aminobenzoic acid, platinum oxide is used Recommended as a catalyst, it is shown that the dimethylamino compound in essential Yield can only be produced in the presence of hydrochloric acid (page 376).

Organic Reactions, Volume IV, page 194 (Wiley, N.Y., 1948) teaches that aromatic amines without substituents in o- and p-positions when treated with formaldehyde resinify in acidic solution.

Aromatic nitro compounds can react with hydrogen in the presence from platinum catalysts and acetic acid only with aldehydes to dialkylarylamines be implemented if the aldehyde used is not formaldehyde.

All of these processes are particularly satisfactory on an industrial scale with respect to simple and economical operation, yield and space-time yield in terms of the end product and the economic viability of the catalyst. The use of hydrochloric acid brings corrosion problems with it. Long response times are sometimes necessary in order to obtain the end product in substantial yield.

The main application P 23 29 553.6 is a method for Production of dimethylaminobenzoic acid esters by reacting nitrobenzoic acid esters with formaldehyde and hydrogen in the presence of hydrogenation catalysts, the Reaction in the presence of a hydrogenation catalyst, one or more metals with contains an atomic number from 24 to 29, and of weak organic acids carried out a temperature of 35 to 150 0C and a pressure of at least 40 at will.

It has now been found that the process of the main application P 23 29 553.6 results in a process for the preparation of dimethylaminobenzene compounds of the formula wherein the individual radicals R1, R2 and R3 can be identical or different and in each case a halogen atom, an aromatic radical, an aliphatic radical, the radical -O-R4, the radical the rest where R4 denotes an aliphatic radical, also denote the individual radicals RO and R3 each for a hydrogen atom or the radical in which R5 denotes an aliphatic, cycloaliphatic, araliphatic or aromatic radical, adjacent radicals Zur or a radical R1 and an adjacent radical R3 together with the two carbon atoms between them can also represent a fused heterocyclic radical, if one can instead of nitrobenzoic acid esters, nitrobenzene compounds of the formula in which R1, R2 and R3 have the abovementioned meaning, is used.

In the case of using p-nitrochlorobenzene, the conversion is represented by the following formulas: Compared to the known processes, the process according to the invention provides dimethylaminobenzene compounds in a simpler and more economical way in better yield, purity and space-time yield. It does not require any expensive catalysts and is particularly suitable as a process that can be used on an industrial scale. Corrosion problems are avoided. All of these advantageous results are surprising in view of the prior art.

The starting materials used are nitrobenzene compounds which, in addition to the nitro group, also have 1 to 5, preferably 1 and 2, substituents on the benzene nucleus; Compounds with a substituent in the m-position and / or a substituent in the p-position to the nitro group are preferred. Preferred starting materials and correspondingly preferred end products are those in whose formulas the individual radicals R1, R2 and Rq can be the same or different and in each case a chlorine atom, a bromine atom, a phenyl radical, an alkyl radical having 1 to 10, advantageously 1 to 4 carbon atoms, the Remainder -OR4, the rest the rest in which R4 denotes an alkyl radical having 1 to 6 carbon atoms, and the individual radicals R2 and R3 each represent a hydrogen atom or the radical where R5 denotes a phenyl radical, an aralkyl radical with 7 to 12 carbon atoms, a cyclohexyl radical, a cyclopentyl radical or in particular an alkyl radical with 1 to 10, advantageously 1 to 4 carbon atoms, adjacent radicals R3 or a radical R1 and an adjacent radical R3 also together with the two carbon atoms between them a fused, 5- or 6-membered, unsaturated or saturated, heterocyclic ring containing a nitrogen atom and / or an oxygen atom and advantageously an oxo group and / or advantageously an alkyl group with 1 to 4 carbon atoms can be substituted, can mean. The aforementioned radicals and rings can also be substituted by organic groups which are inert under the reaction conditions, e.g. alkyl groups with 1 to 4 carbon atoms, carbalkoxy groups with 2 to 4 carbon atoms -Acetamido-, 4-methoxy-, 4-methyl-, 4-phenyl-, 4-propylcarbonyl-, 4-butoxy-, 4-isopropoxy-, 4-tert-butoxy-, 4-thylcarbonyl-, 4-hexylcarbonyl -, 4-propionic acid amido-.

4-butylcarbonamido, 4-ethyl, 4-isopropyl, 4-propyl, 4-butyl, 4-decyl-, 4-hexyl-, 4-isobutyl-, 4-tert-butyl-nitrobenzene and the corresponding in 2- or 3-position instead of nitrobenzenes substituted in 4-position; with same or different, aforementioned substituents substituted in the 3- and 4-position Nitrobenzenes such as 3,4-dichloro-, 3,4-dimethoxy-, 4-ethyl-3-butoxy-, 3-acetamido-4-phenyl-nitrobenzene; the phenyl, benzyl, cyolohexyl, cyclopentyl, tert-butyl, methyl, xthyl, Propyl, isopropyl, p-ethylphenyl, p-carbmethoxyphenyl, isobutyl, n-butyl esters the 4- and especially 3-nitrobenzoic acid, the 3- or 4-position with the aforementioned Substituents are substituted; with the same or different ones mentioned above Substituents correspondingly simultaneously in 2- and 3-, 2- and 4-, 2- and 5-, 2- and 6-, 3- and 5-position or simultaneously in 2-, 3- and 4-position or in 2-, 3- and 5-position or in 2-, 3- and 6-position or in 3-, 4- and 5 position or in the 2-, 4- and 6-position or simultaneously in the 2-, 3-, 4- and 5-position or nitrobenzenes substituted in the 2-, 3-, 5- and 6-position or in the 2-s 3-, 4- and 6-position; 6-nitro-, 7-nitro-, 5-nitro-benzoxazole, corresponding 2-oxo-, 2-methyl-, 2-butyl-benzoxazoles and corresponding coumarins, benzofurans, indoles, indolines, isoindolines, chromans, Quinolines, isoquinolines.

The formaldehyde can be used as a gas, in alcoholic, e.g. methanolic Solution, or preferably in the form of its aqueous solution, expediently in 30 to 40 percent by weight aqueous solution can be used. The starting material can with formaldehyde in a stoichiometric amount or in excess, preferably in one Ratio of 2 to 8, in particular 2 to 3 moles of formaldehyde per mole of starting material II, to be implemented 0 The reaction is carried out at a temperature of 35 to 15000, preferably 45 to 95 ° C, in particular from 45 to 70 ° C and a pressure of at least 40, preferably 50 to 250, advantageously 70 to 150, in particular 70 to 110 at, carried out continuously or discontinuously. Appropriately one uses under Organic solvents which are inert to the reaction conditions, e.g.

Alkanols, in particular with 1 to 4 carbon atoms such as methanol, Ethanol, isopropyl alcohol; Glycols, e.g., methylethylene glycol; Tetrahydrofuran; or corresponding mixtures, advantageously in amounts of from 200 to 1,000% by weight, in particular 200 to 400% by weight, based on starting material II.

The reaction is carried out in the presence of weak organic acids, generally with a dissociation constant of at least 1.5. 10-4, preferably from 1.5 10-4 to 1. 1-6, especially from 1.5 10-4 to 1. 10. Preferred Acids are aliphatic carboxylic acids having 3 to 10 carbon atoms, preferably corresponding alkanecarboxylic acids optionally substituted by hydroxyl groups or cyano groups or alkene carboxylic acids, advantageously monocarboxylic acids or dicarboxylic acids, such as propionic acid, Butyric acid, acrylic acid, maleic acid, crotonic acid, isocrotonic acid, vinyl acetic acid, Succinic acid, isobutyric acid, angelicic acid, tiglic acid, levulinic acid, Glutaric acid, Valeric acid, isovaleric acid, trimethyl acetic acid, adipic acid, caproic acid, Diethyl acetic acid, enanthic acid, pelargonic acid. But you can also use formic acid, Acetic acid, lactic acid, cycloaliphatic carboxylic acids such as cyclopropanecarboxylic acid, Cyclobutanecarboxylic acid, cyclohexanecarboxylic acid, uric acid, heterocyclic carboxylic acids such as furan-2-carboxylic acid, aromatic carboxylic acids such as benzoic acid, m-hydroxybenzoic acid, Terephthalic acid, phenylacetic acid, p-toluic acid, p-methoxybenzoic acid, cinnamic acid, Use palmitic acid, cholic acid.

Alkanecarboxylic acids with 3 to 8 carbon atoms are particularly advantageous, in particular propionic acid. In general, amounts from 0.1 to 0.5 are preferred from 0.1 to 0.3 mol of acid, based on 1 mol of starting material II, into consideration.

The hydrogenation catalysts are generally one or more metals with an ordinal number between 24 and 29, preferably cobalt, copper, manganese and / or nickel catalysts, e.g. corresponding sintered catalysts O The metals can also be used in the catalyst in the form of their oxides and / or as a mixture with phosphoric acid are present. Advantageous catalysts of the type mentioned contain between 3 and 30 wt. Copper and / or cobalt, 0.5 and 10 total;% manganese and 10 and 80 total 9% nickel In addition, 0.1 to 5% by weight of phosphoric acid, based on the amount of metal, may be added.

The hydrogenation catalyst is usually in the implementation in a Amount from 0.5 to 50, preferably from 2 to 30% by weight, in the case of Raney nickel Preferably from 2 to 5% by weight, based on starting material II, is used, it can in a mixture with a carrier material suitable for the reaction, e.g. silicon dioxide, are used, the amount of catalyst generally being 10 to 40 Total% of the mixture of catalyst and support. There are, for example, the following catalyst mixtures suitable: a) 70> 5% Ni, 19.7% Co, 5.4 ffi Mn, 4.2% phosphoric acid b) 15% Ni, 6.1% Cu, 1.5% Mn, 0.9% phosphoric acid on SiO2 c) 15% Ni, 5.2%. Cu, 1.3% Mn on Ski02.

Raney nickel is particularly advantageous. Usually the reaction mixture at the beginning and in the course of the reaction, such amounts of hydrogen are supplied that A corresponding reaction pressure is always appropriate at the reaction temperature between 40 and 150 at. You can also use inert gases such as nitrogen can be used. The residence times in the reaction space are usually between 15 and 600 minutes.

The reaction can be carried out as follows: The starting material is added II and the formaldehyde, optionally together with the solvent, in one Reactor, adds the catalyst and the acid and flushes the reaction space with it Nitrogen.

Then hydrogen is injected up to the aforementioned reaction pressure. The reaction mixture is now brought to the aforementioned temperature and at this temperature is maintained with the introduction of further hydrogen until no hydrogen more is consumed by the reaction o The reaction mixture is now cooled and filtered. The end product is obtained from the filtrate by the customary methods, e.g. by fractional distillation or addition of water, separation of the organic lower phase from the two-phase mixture formed and fractional distillation, severed.

The compounds preparable by the process of the invention are valuable starting materials for the synthesis of dyes, especially crystal violet brands and reactive dyes, and pesticides. For example, you can according to the process described in Belgian patent 640 930 as stabilizers serve for unsaturated polyester resins. Regarding the use, reference is made to the aforementioned Publications referenced.

The especially halogen-substituted dimethylanilines are used as photoinitiators (U.S. Patent 3,515,552 and U.S. Patent 3,539,346) in photosensitive Compositions for the production of galvanic metal coatings (DRP 934 508) and in the production of moldings with poly (methyl) methyl acrylates (GDR patent 17 190).

The parts listed in the following examples are parts by weight. They relate to parts by volume like the kilogram to the liter.

Example 1 p-Dimethylamino-chlorobenzene 79 parts of p-nitrochlorobenzene are suspended in 480 parts of methanol and, after the addition of 120 parts, aqueous Formalin solution (40 percent), 23 parts of propionic acid and 12 parts of Raney nickel hydrogenated at 800C and 100 at hydrogen pressure. After the hydrogen uptake has ceased the mixture is filtered off from the catalyst and the solvent is distilled off The residue is distilled in vacuo. 64 parts of p-dimethylaminochlorobenzene are obtained at 50 to 530C / 0.2 Torr (melting point 33 to 350C), this corresponds to a yield out of 82 of theory.

Example 2 p-Dimethylamino-bromobenzene 100 parts of p-nitrobromobenzene are dissolved in 480 parts of methanol and 200 parts of tetrahydrofuran and after addition of 120 parts of aqueous formalin solution (40 percent), 23 parts of propionic acid and 12 parts of Raney nickel hydrogenated at 80 ° C. and 100 atm. Hydrogen pressure. After completion the hydrogen uptake, the mixture is separated from the catalyst and the solvent distilled off. The precipitated crystals are used to remove propionic acid Stirred with 500 parts of water and filtered off with suction. 78 parts of p-dimethylamino-bromobenzene are obtained from melting point 47 to 49 ° C, corresponding to a yield of 78% of theory.

Example 3 3, 4-dichloro-dimethylaniline 96 parts of 1,2-dichloro-4-nitrobenzene are suspended in 480 parts of methanol and, after the addition of 120 parts, aqueous Formally in solution (40 percent), 23 parts of propionic acid and 12 parts of Raney nickel hydrogenated at 90 ° C and 100 at hydrogen pressure.

After the uptake of hydrogen has ceased, the mixture is as in Example 1 described, worked up. 75 parts of 3,4-dichloro-dimethylaniline are obtained Boiling point 98 to 1030C at 0.4 Torr and the melting point 31 to 3500. This corresponds to a yield of 79% of theory.

Example 4 4-Dimethylamino catechol dimethyl ether 64 parts of 4-nitro catechol dimethyl ether are suspended in 560 parts of methanol and, after the addition of 90 parts, aqueous Formalin solution (40 percent), 18 parts of propionic acid and 9 parts of Raney nickel hydrogenated at 600C and 100 at hydrogen pressure. After working up as in the example 1 gives 54 parts of 4-dimethylamino-catechol dimethyl ether with a melting point 39 to 4300. This corresponds to a yield of 86% of theory.

Example 5 4-Dimethylamino-acetanilide 90 parts of p-nitro-aoetanilide are suspended in 640 parts of methanol and after the addition of 120 parts of formalin solution (40 percent), 23 parts of propionic acid and 12 parts of Raney nickel at 600C and 100 hydrogenated at hydrogen pressure. The work-up is carried out as in Example 2. This gives 72 parts of 4-dimethylaminoacetanilide with a melting point of 126 to 12900. This corresponds to a yield of 81% of theory.

Example 6 6-Dimethylamino-benzoxazolone-2 90 parts of 6-nitro-benzoxazolone-2 are suspended in 200 parts of tetrahydrofuran and 500 parts of methanol and after Addition of 120 parts of formalin solution (40 percent), 23 parts of propionic acid and Hydrogenated 12 parts of Raney nickel at 60 ° C. and 100 atm. Hydrogen pressure. After completion the hydrogen uptake will reduce the mixture to half of its original volume concentrated and the precipitated end product is filtered off with suction. 69 parts of 6-dimethylaminobenzoxazolone-2 are obtained from a melting point of 150 to 1540 ° C., corresponding to a yield of 77% of theory.

Example 7 6-Dimethylamino-2-methyl-benzoxazole 53 parts of 6-nitro-2-methyl-benzoxazole are suspended in 500 parts of methanol and 300 parts of tetrahydrofuran and after Addition of 72 parts of aqueous formalin solution (40 percent) and 14 parts of propionic acid and 7 parts of Raney nickel hydrogenated at 60 ° C. and 100 atm. hydrogen pressure. Work-up takes place analogously to Example 2. 41 parts of 6-dimethylamino-2-methylbenzoxazole are obtained Melting point 82 to 860 ° C., corresponding to a yield of 78% of theory.

Example 8 4-Dimethylamino-anisole 153 parts of p-nitroanisole become suspended in 800 parts of methanol and after the addition of 225 parts of aqueous formalin solution (40 percent), 33 parts of propionic acid and 14 parts of Raney nickel at 80 ° C and 100 hydrogenated at hydrogen pressure. The work-up is carried out in the same way as in Example 1. This gives 124 parts of 4-dimethylamino-anisole from melting point 42 to 4500, corresponding to one Yield of 82% of theory.

Example 9 4-Dimethylaminotoluene 137 parts of p-nitro-toluene become suspended in 800 parts of methanol and after the addition of 225 parts of formalin solution (40 percent), 33 parts of propionic acid and 14 parts of Raney nickel at 600C and 100 hydrogenated at hydrogen pressure. The work-up is carried out in the same way as in Example 1. This gives 110 parts of 4-dimethylaminotoluene with a boiling point of 115 to 1170C at 40 Torr (n21s5 = 1.5480), corresponding to a yield of 81% of theory.

Example 10 4-Dimethylamino-diphenyl 100 parts of 4-nitro-diphenyl become suspended in 500 parts of methanol and 200 parts of tetrahydrofuran and after addition of 120 parts of formalin solution (40 percent), 23 parts of propionic acid and 12 parts Raney nickel hydrogenated at 800C and 100 at hydrogen pressure. After the Hydrogen uptake will reduce the mixture to half of its original volume concentrated and the precipitated end product is suctioned off. 92 parts of 4-dimethylaminodiphenyl are obtained from melting point 119 to 1210C, corresponding to a yield of 93% of theory.

Claims (1)

Claim Process for the preparation of dimethylaminobenzene compounds of the formula wherein the individual radicals R1, R2 and R3 can be identical or different and each represents a halogen atom, an aromatic atom denote, in addition, the individual radicals RO and RX each for a hydrogen atom or the radical where R5 denotes an aliphatic, cycloaliphatic, araliphatic or aromatic radical, adjacent radicals R or a radical R1 and an adjacent radical R3 together with the two carbon atoms between them can also represent a fused heterocyclic radical, according to the procedure for preparation of dimethylaminobenzoic acid esters by reacting nitrobenzoic acid esters with formaldehyde and hydrogen in the presence of hydrogenation catalysts, the reaction in the presence of a hydrogenation catalyst containing one or more metals with an atomic number of 24 to 29, and of weak organic acids at a temperature of 35 to 1500C and a pressure of at least 40 at, according to patent application P2329553.6, characterized in that instead of nitrobenzoic acid esters, nitrobenzene compounds of the formula in which R1, R2 and R3 have the abovementioned meaning, is used.