CH615427A5 - Process for the preparation of 2-aryl-2H-benzotriazoles - Google Patents

Description

The invention relates to a process for the preparation of 2-aryl-2H-benzotriazoles and derivatives thereof, in which high yields of the desired products are obtained and problems of environmental pollution, as they involve previously known processes, are avoided.

So far, the conversion of an ortho-nitroazobenzene into the corresponding 2-aryl-2H-benzotriazole has been carried out by chemical or electrolytic reduction. E.g. describe the U.S. Patents 3 072 585 and 3 230 194 such as o-nitroazobenzene derivatives can be converted chemically with zinc in alcoholic sodium hydroxide solution in good yields into the corresponding 2-aryl-2H-benzotriazoles. Ammonium sulfide, alkali sulfide, zinc with ammonia at 80 to 100 ° C, sodium hydrosulfide and zinc with hydrochloric acid have also been used as chemical reducing agents for the conversion, see U.S. Patent 2,362,988. The use of ammonium sulfide was also discussed by S.N. Chakra-Barty et al, J. Jndian Chem. Soc., 5, 555 (1928), Chem. Abst., 23, 836, (1929) reported with different results, depending on the presence or absence of substituents on the 2-aryl -Group. In some cases, the desired 2-aryl-2H-benzotriazoles were not formed at all as reduction products, but rather only the corresponding o-aminoazobenzenes.

H. Itomi, Mem. Coli describes the electrolytic reduction of o-nitroazobenzenes. Be. Kyoto Imp. Univ., 12A, No. 6, 343 (1929), Chem. Abst., 24, 2060 (1930), using a copper cathode in dilute sodium hydroxide solution. The yields vary from 25-60%, depending on the particular circumstances, with one major by-product being the corresponding o-aminoazobenzene.

The widely used zinc dust and sodium hydroxide chemical reduction system for converting o-nitro-abozenzenes into the corresponding 2-arvl-2H-benzotriazoIe are described by K. Elbs, et al, J. Prakt. Chem., 108, 204 (1924), Chem. Abst., 19, 514 (1925). The yields of the desired 2-aryl-2H-benzotriazole vary from 30-85%, depending on the o-nitroazobenzene intermediate which is reduced.

The known chemical and electrolytic reduction processes for the preparation of 2-aryl-2H-benzotriazoles are often not practical or economical. The widespread zinc dust and sodium hydroxide system poses environmental pollution problems, particularly the waste disposal of zinc sludge, which is becoming an increasing concern for the environment.

The Japanese OS Sho 48-26012 from 3.8 describes the production in good yields of isomeric but chemically different 1 H-benzotriazoles by catalytic reduction in an alkaline medium from o-nitrophenylhyrazine and certain alkyl and perfluoroalkyl derivatives thereof substituted on the phenyl ring. 1973. The isomeric 2H-benzotriazoles of the present invention cannot be prepared from phenylhydrazines.

The object of the invention was therefore to create a new process for the preparation of 2-aryl-2H-benzotriazoles which avoids the waste problems.

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The aim was to prepare 2-aryl-2H-benzotriazoles by reduction and cyclization of the corresponding o-nitroazobenzoic acid under certain conditions, as specified in more detail below, high yields being obtained in acceptable purity.

The invention particularly relates to a process for the preparation of 2- (2-hydroxy-5-methylphenyl) -2H-benzotriazzo, characterized in that 2-nitro-2'-hydroxy-5'-methylazobenzene with hydrogen in an organic solvent mixture containing an amine or ammonia is reduced and cyclized in the presence of a noble metal hydrogenation catalyst from group VIII of the periodic table, and the desired 2- (2-hydroxy-5-methyl) -2H-benzotriazole is isolated.

The process is characterized in that 2-nitro-2'-hydroxy-5'-methylazobenzene is hydrogenated at 20 to 100 ° C. and 1 to 66 atmospheric pressure in an organic solvent mixture containing toluene and methanol and with a water-soluble amine, such as diethylamine, treated in the presence of a hydrogenation catalyst comprising a noble metal from group VIII of the periodic table, filtering off the noble metal catalyst, isolating a crude product by distillation, removing the amine impurities from the crude product by acid extraction, and the desired 2- (2-hydroxy-5 -methylphenyI) -2H-benzotriazole isolated in the usual way.

The inventive method will be carried out at a temperature of about 20 ° C to about 100 ° C, in particular about 30 ° C to about 80 ° C, especially at about 40 ° C to about 70 ° C.

In particular, the invention relates to a process for the preparation of 2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole, characterized in that 2-nitro-2'-hydroxy-5'-methylazobenzene with hydrogen about 20 ° C to about 100 ° C and about 1 to about 66 atmospheres in an organic solvent mixture containing toluene, methanol and diethylamine in the presence of a palladium on charcoal hydrogenation catalyst, and the desired 2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole isolated.

The reductive cyclization of 2-nitro-2'-hydroxy-5'-methylazobenzene is preferred dissolved in a toluene / methanol solution containing 0.925 equivalents of the water-miscible amine, diethylamine, per mole of o-nitroazobenzene.

With less soluble and more hydrocarbon-like 2-aryl-2H-benzotriazoles and the corresponding o-nitro-azobenzene starting materials, it is advantageous to use other organic solvents that better dissolve these substances in the reaction medium, such as isopropanol and additional amounts of amines.

In particular, the invention further relates to the preparation of 2- (2-hydroxy-3,5-di-tert-amylphenyl) -2H-benzotriazole by reductive cyclization of 2-nitro-2'-hydroxy-3 ', 5'-di- -tert-amylazobenzene dissolved in isopropanol with 1.1 moles of diethylamine or another amine per mole of o-nitroazobenzene starting material.

With these hydrocarbon-like compounds, the hydrogen absorption is often considerably higher than according to theory, which indicates that a further reduction in the desired product may have taken place.

Further embodiments of the invention are shown in the following detailed description.

The reduction of 2-nitro-2'-hydroxy-5'-methyl azobenzene is carried out in a mixture of toluene, methanol and diethylamine with enough methanol to ensure a liquid phase in the system, with 2 moles of water per mole of azobenzene arise in the system during the reduction, and are provided with sufficient (about 0.9 moles per mole of azobenzene) diethylamine to maintain a strongly alkaline environment. Palladium on carbon is used as the hydrogenation catalyst. The reduction and cyclization is carried out at a hydrogen pressure of about 1 to about 5.7 atmospheres and about 20 ° C to about 100 ° C. The pure product is isolated in yields of 75% or more. Higher pressures up to about 66 atmospheres can be used as well.

Similarly, the reduction of 2-nitro-2 '- hydroxy-3', 5'-di-tert-amylazobenzene in a solution of isopropanol with at least 1.1 moles of diethylamine per mole of azobenzene is carried out to create a strongly alkaline medium to accomplish. A preferred hydrogenation catalyst is palladium on alumina.

The catalysts used for the reduction of o-Ni-troazobenzenes to 2-aryl-2H-benzotriazoles are noble metals from group VIII of the periodic table, preferably palladium, but also others, such as platinum, rhodium, ruthenium, osmium and iridium, but the results thereof are not necessary are the same. The metals can be used as such, or as oxides, or in particular on solid supports, such as carbon, silicon dioxide or aluminum oxide, especially activated carbon or aluminum oxide. Very small amounts of catalyst are required to carry out the reductive cyclization, such as 0.001 to 0.005 mol / mol o-nitroazobenzene. More catalyst can be used, but over 0.01 mol / mol o-nitroazobenzene is generally neither useful nor economically viable.

In general, the noble metal catalysts can be interchanged. However, there are some differences between the individual metals. If the o-nitro-azobenzene starting material is chlorine-substituted, the use of a palladium catalyst leads to the reductive cyclization to the 2-aryl-2H-benzotriazole, but the chlorine is also split off. Replacing palladium with rhodium, a milder, more selective catalyst, gives 2-aryl-2H-benzotriazoles, which still contain chlorine. If the production of a 2-aryl-2H-benzotriazole containing chlorine is intended in one or both of the aromatic rings, a rhodium catalyst and not a palladium catalyst should be used, preference being given to rhodium on activated carbon.

An important feature of the invention is that the noble metal catalyst can be reused for the reductive cyclization without a noticeable loss of reactivity. Up to 10 approaches were run with excellent results.

As said, the reduction is carried out at about 20 ° C to about 100 ° C and about 1 to about 66 atmospheres with sufficient organic solvent such as toluene to keep the starting material and product in solution and with a water-miscible organic medium such as methanol, so that the water of reaction remains in only one liquid phase in the system and with an organic amine such as diethylamine to create a strongly alkaline environment so that the desired reaction proceeds with a minimum of by-product impurities. The desired reaction does not take place without the amine.

The organic solvents used to dissolve the o-nitroazobenzene intermediates and the corresponding 2-aryI-2H-benzotriazoIe can be non-polar hydrocarbons, such as benzene, toluene, xylene, cyclo-hexane, aliphatic hydrocarbons, such as hexane, Heptane, petroleum ether and other hydrocarbons and mixtures thereof. For economic reasons, because of the handling and accessibility, toluene is preferred.

Since water is generated in the cyclization reaction, it is necessary to use a water-miscible solvent or co-solvent to do everything except the dispersing agent.

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to keep the catalyst in a liquid phase. This is particularly necessary if the above non-polar solvents are used. Water-miscible solvents or co-solvents are e.g. Alcohols such as methanol, ethanol, isopropanol, n-propanol, n-butanol and methyl cellosolve (2-methoxyethanol), especially methanol with non-polar co-solvents, or isopropanol alone.

Other suitable water-miscible solvents or co-solvents are ethers such as tetrahydrofuran, 1,4-di-oxane, 1,2-dimethoxyethane, 1,2-diethoxyethane and the like.

Other suitable solvents are trialkyl phosphates, such as triethyl phosphate, tributyl phosphate, trioctyl phosphate and the like.

The reductive cyclization of the o-nitroazobenzenes to the corresponding 2-aryl-2H-benzotriazoles requires a strongly alkaline environment. The desired reaction does not occur in the absence of an amine or ammonia. Suitable amines are especially water-miscible, as justified above, although other amines can also be used if sufficient water-miscible solvent or co-solvent is present. Amines are e.g. primary, secondary or tertiary aliphatic amines with in particular C, -C, alkyl groups, e.g. Ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, propylamine, i-propylamine, di-i-propylamine, butylamine, octylamine, cyclo-hexylamine, ethanolamine, diethanolamine, triethanolamine and also piperidine, hydroxypiperdin, piperazine, morpholine, pyrrolidine, guanidine and the like For economic reasons, because of the handling and accessibility, morpholine, piperidine and lower dialkylamines such as diethylamine, dimethylamine, di-n-propylamine and the like are preferred, especially diethylamine.

The reductive cyclization reaction can be carried out at various solvent concentrations, co-solvent and amine concentrations.

Since the reductive cyclization reaction does not take place without a strongly alkaline medium, as created by one or more of the above amines, it is often suitable to carry out the process in such a way that the organic solvent consists entirely of an amine alone. Then a molar excess of amine relative to the o-nitroazo-benzene is expediently always present. This solvent system has the advantage of being easy to work up when the reaction is complete, since there are no solvent mixtures. Amines with particularly good consideration of base strength, solution character, physical properties, good handling, accessibility and practicability in the process according to the invention are n-propylamine, diethylamine, triethylamine, isopropylamine, n-butylamine, di-butylamine, tert-butylamine, amylamine, morpholine and the like .

The required amount of amine is at least 0.1 mole of amine per mole of o-nitroazobenzene intermediate, in particular at least 0.9 mole per mole of o-nitroazobenzene intermediate. Additional amounts of amine can be used, but over 1.5 moles / mole of o-nitroazobenzene is neither necessary nor economical.

The concentrations (weight) of o-nitroazobenzene intermediate in the organic solvent system range from dilute solutions, about 5-10%, to concentrated solutions, at 20-30%. Concentrated solutions are preferred for economic reasons.

The organic solvent system can contain 100% of a water-miscible organic alcohol or ether without a non-polar co-solvent.

These systems can also contain a mixture of non-polar organic solvent with a water-miscible organic co-solvent, especially trialkyl phosphate, the maximum amount of non-polar solvent in the entire solvent system being about 65-75% (weight). Examples of non-polar solvents are hydrocarbons, such as benzene, toluene, xylene, mesitylene.

For many 2-aryl-2H-benzotriazoles, a toluene / methanol / diethylamine mixture is preferred, in particular because of the conveniently located boiling points, which allow it to be easily recovered by distillation for recycling after removal of the water of reaction. If this organic solvent mixture is used, the catalyst can be filtered off and recycled at the end of the reduction and cyclization reaction, a particular advantage, while the desired 2-aryi-2H-benzotriazole product remains in the organic solution.

Isolation of a product in good yield and acceptable purity is another feature of the invention. The organic solution of the desired 2-aryl-2H-benzotriazole after filtering off the noble metal catalyst is distilled to remove the organic solvents and small amounts of water that are formed in the reduction. A crude product is obtained in 75-85% yield, which contains some amine by-product impurities. The crude product can be suitably purified by dissolving it in toluene, removing the amine impurities by extraction with aqueous mineral acid, in particular 70% sulfuric acid, and isolating it again in the usual way. A purified product of high purity is obtained in yields of 70-80%. Various by-products are formed in trace amounts during the reduction of o-nitroazobenzenes, such as corresponding o-aminoazobenzenes, o-amino-hydrazobenzenes, o-phenylenediamines, anilines, aminophenols and 1,2,3-benzotriazoles. Most of these contaminants are removed by acid washing, especially with sulfuric acid.

In the case of 2-aryl-2H-benzotriazoles, such as 2- (2-hydroxy-3,5-di-tert-amylphenyl) -2H-benzotriazoles, the crude products are obtained in yields of 52-67%. These contain slightly more amine by-products than in the case of 2 - (2-hydroxy-5-methyIphenyI) -2H-benzotriazoI. However, these amine by-products are removed as above by dissolving the crude product in an organic solvent such as petroleum ether, extracting with aqueous mineral acid and isolating the desired product in high purity in a customary manner and in good yields.

The process according to the invention can be carried out in any suitable manner, either batchwise or continuously. If the process is started, e.g. a quantity of hydroxy-substituted o-nitroazobenzene, toluene, methanol and diethylamine with the catalyst, such as palladium on activated carbon, in a suitable apparatus, such as a shaking or stirring autoclave. Hydrogen is injected until the desired initial pressure is reached. The autoclave with contents is then heated, if desired, and kept agitated at the desired temperature until the theoretical amount of hydrogen is absorbed, whereupon no further hydrogen is taken up. The reduction reaction is complete. The excess pressure is then released and the solution, which is generally still warm, is filtered, in particular under an inert atmosphere, such as under nitrogen or argon, in order to remove the catalyst. The solution is then distilled. A crude product is obtained, which can be further purified by dissolving in toluene, extracting with aqueous acid and recrystallizing from an organic solvent.

The invention also relates to the production of 2-aryl-2H-benzotriazoles by reduction and cyclization of o-nitroazobenzenes in a continuous manner, although not necessarily with the same result. For example,

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in the continuous mode of operation, the hydroxy-substituted o-nitroazobenzoI starting material is premixed and dissolved in an organic solvent mixture which contains a water-soluble amine. This mixture is continuously brought into a reaction zone which is kept at the correct working temperature and pressure and contains the hydrogenation catalyst. Hydrogen is introduced separately into the reaction zone. After the desired residence time, the effluent is withdrawn continuously. The removed solution is distilled to isolate the desired product. Because of the nature of the catalyst, it is particularly suitable to use a catalyst on a fixed bed in the descending or ascending flow of the reaction solution. If the reduction is to be carried out as a 2-step process with different temperatures in each step, 2 reaction zones are used in series, which work at the preferred temperatures of the respective reduction step.

The reduction of o-nitroazobenzenes to the corresponding 2-aryl-2H-benzotriazoles is a 2-step process as follows:

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Step 1 - The reduction of the o-nitroazobenzene to the N-oxybenzotriazole derivative proceeds quickly and exothermically even at low temperature under the conditions according to the invention.

Step 2 - The reduction of the N-oxybenzotriazole intermediate to the corresponding 2-aryl-2H-benzotri-azole product is slower. This reduction can be accelerated considerably by adding more catalyst, as well as by increasing the temperature, the hydrogen pressure or both.

In general, the reaction stops when the N-oxy intermediate is completely reduced to the corresponding 2-aryl-2H-benzotriazoI. This makes it easy to control this catalytic hydrogenation. For some highly substituted benzotriazoles, however, the reduction should be terminated as soon as the appropriate amount of hydrogen has been absorbed and reacted to avoid further reductive cleavage of the 2-aryl-2H-benzotriazole produced.

The invention relates to a process for the preparation of compounds of the formula I.

OH

N

wherein

R is hydrogen or chlorine,

R-, hydrogen, chlorine, C, -C1-alkyl, C, -C.1-alkoxy, C ..- C ,, - carboalkoxy, carboxy or -S03H,

R3 C, -Clïï-alkyl, CrQ-alkoxy, phenyl, phenyl substituted with C, -C, -alkyl, C -, - C, - cycloalkyl, C, -C ,, - carboalkoxy, chlorine, carboxyethyl or C, -C., - arylalkyl,

R is hydrogen, C, -C., - alkyl, C, -C., - alkoxy, chlorine or hydroxy, and

R-, hydrogen, C, -Cr2-alkyl, chlorine, C-C, -cycloalkyl or C7-C., - arylalkyl.

R. can be used as C, -C, alkyl e.g. be: methyl, ethyl or n-butyl. R. can be used as C, -Cralkoxy e.g. be: methoxy,

Ethoxy or n-butoxy. R., can be used as C2-C ,, carboalkoxy e.g. be: carbomethoxy, carboethoxy or carbo-n-octoxy.

R: î can be C 1 -C 4 -alkyl, such as methyl, ethyl, sec-butyl, tert-butyl, amyl, tert-octyl or n-dodecyl. R3 can also be C, -C, alkoxy, such as methoxy, ethoxy, n-butoxy. R :! can also be phenyl substituted with C, -CH-alkyl, such as with methyl, tert-butyl, tert-amyl or tert-octyl. R;, can also be C .-- Ci; Be cycloalkyl, such as cyclopentyl or cyclohexyl. R3 can also be C 1 -C 4 carboalkoxy, such as carbomethoxy, carboethoxy, carbo-n-butoxy or carbo-n-octoxy. R3 can also be Cr-C., Arylalkyl, such as benzyl, a-methylbenzyl or a, a-dimethylbenzyl.

R, can be C, -C. Alkyl, such as methyl, ethyl or n-butyl. R, can also be C, -Cralkoxy, such as methoxy, ethoxy or n-butyloxy.

R- can be C, -C, .j-alkyl, such as methyl, sec-butyl, tert-butyl, tert-Amvl or tert-octyl. R-, can also be C;, - C, - cycloalkyl, such as cyclopentyl or cyclohexyl. R-, can also be C7-C., - arylalkyl, such as benzyl, a-methylbenzyl or a, a-dimethylbenzyl.

Rj is preferably hydrogen.

R. is preferably hydrogen, chlorine, C 1 -C 2 -alkyl, methoxy or carboxy.

R3 is preferably C 1 -C 12 -alkyl, cyclohexyl, phenyl, chlorine, a-methylbenzyl or carboxyethyl.

R4 is preferably hydrogen, hydroxy or methyl.

R-, hydrogen, chlorine, CrC12-alkyl, cyclohexyl, benzyl or a-methylbenzyl is preferred.

Ro is particularly preferably hydrogen or chlorine.

R3 is particularly preferably methyl, tert-butyl, tert-amyl, tert-octyl, sec-butyl, cyclohexyl, chlorine or carboxyethyl.

R is particularly preferably hydrogen.

Rr, hydrogen, chlorine, methyl, sec-butyl, tert-butyl, tert-amyl, tert-octyl or a-methyl-benzyl is particularly preferred.

The process involves the reduction of an o-nitro-azobenzene intermediate of formula II

OH

N

R

wherein R ,, R., R3, R, and R. ^ have the above meaning as described in claim 1.

The nitroazobenzene intermediates are prepared by the corresponding o-nitroazobenzene diazonium compound of the formula III

© 0

.N = N X

R

■ 2

where Rj and R. have the above meaning and X is chloride, sulfate or another anion, in particular chloride, with a phenol of the formula IV

OH

R

converts, which couples in the ortho position to hydroxy.

The o-nitrobenzene diazonium compounds are in turn prepared by customary diazotization with sodium nitrite in acid solution with the corresponding o-nitroanilines of the formula V.

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4-ethyl-2-nitroaniline n-butyl-3-nitro-4-aminobenzoate n-octyl-3-nitro-4-aminobenzoate

4-n-butoxy-2-nitroaniline

3-nitro-4-aminobenzoic acid

3-nitro-4-aminobenzenesulfonic acid.

Preferred suitable compounds of formula V are o-nitroaniline

4-chloro-2-nitroaniline.

produced.

Some specific examples of compounds of the formulas IV and V are given for illustration. These are generally commercially available.

Compounds of formula IV p-cresol

2,4-di-tert-butylphenol

2,4-di-tert-amylphenol

2,4-di-tert-octylphenol

2-tert-butyl-4-methylphenol

4-cyclohexylphenol

4-tert-butylphenol

4-tert-amylphenol

4-tert-octylphenol

2,4-dimethylphenol

3,4-dimethylphenol

4-chlorophenol

2,4-dichlorophenol

3,4-dichlorophenol

4-phenylphenol

4-phenoxyphenol

4-o-tolylphenol

4- (4'tert-octyl) phenylphenol

Ethyl 4-hydroxybenzoate n-octyl 4-hydroxybenzoate

4-methoxyphenol

4-n-octylphenol

4-n-dodecylphenol

Resorcinol

4- (a-methylbenzyl) phenol

2- (x-methylbenzyl) -4-methylphenol

2-cyclohexyl-4-methylphenol

4-sec-butylphenol

2-sec-butyl-4-tert-butylphenol

2-tert-butyl-4-sec-butylphenol

4-carboxyithylphenol

2-methyl-4-carboxyethyIphenol.

Preferred suitable compounds of formula IV are p-cresol

2,4-di-tert-butylphenol 2,4-di-tert-amylphenol

2,4-di-tert-octylphenol 2-tert-butyi-4-methylphenol 4-tert-octylphenol 4-n-octylphenol 4-n-dodecylphenol resorcinol

2-sec-butyl-4-tert-butylphenol 2- (a-methylbenzyl) -4-methylphenol.

Compounds of the formula V o-nitroaniline 4-chloro-2-nitroaniline

4.5-dichloro-2-nitroaniline 4-methoxy-2-nitroaniline 4-methyl-2-nitroaniline

The 2-aryl-2H-benzotriazoles are widely used as an intermediate dye, optical brighteners, blue fluorescent agents and selective UV light-absorbing stabilizers for the effective protection of fibers, films and various polymeric structures which are subject to destruction by UV radiation. These substances are important commercial products.

The 2-aryl-2H-benzotriazoles are complex organic molecules that require careful synthetic procedures for their preparation in good yields and acceptable purity.

The invention relates to a process for the preparation of 2-aryl-2H-benzotriazoles. These are characterized by very low absorption in visible light and great light protection in various substrates. Particularly valuable stabilizers of this type are compounds with free hydroxy in the 2-position of the aryl, which is bonded to the 2-N atom of benzotriazole, and which are substituted in the 3- and 5- or 4- and 30 5-position by lower alkyl , and can be substituted by chlorine in the 5-position of the benzotriazole nucleus.

The description, preparation, and use of these valuable substituted 2-aryl-2H-benzotriazoles is still ongoing in U.S. Pat. Patents 3,004,896, 3,055,896, 3,072,585, 3,074,910, 3,189,615 and 3,230,194.

Particular advantages of the process according to the invention are the high purity of the desired triazole, the high yields, the possibility of recycling the reaction medium in particular after removal of the water of reaction, if appropriate after distillation, and the maintenance of the catalyst activity, which is only slightly reduced . Therefore the catalyst can also be recycled, possibly together with small fresh amounts, e.g. about 10% (weight 45) fresh catalyst. The reaction times are reduced compared to a process in an aqueous reaction medium.

The following examples illustrate the process according to the invention without restricting the scope of the invention.

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example 1

2- {2-Hydroxy-5-methylphenyl) -2H-benzotriazole

55 In a 1 liter low-pressure hydrogenation reactor, 20 g of 2-nitro-2'-hydroxy - 5'-methylazobenzene (95% pure) are dissolved in 55 g of toluene, 25 g of methanol and 5 g of diethylamine and 1 , 5 g of 5% palladium on activated carbon hydrogenation catalyst and slurried in the organi-60 see solvents. The amount of catalyst is 7.5% based on the azobenzene intermediate. The molar ratio of diethylamine to azobenzene intermediate is 0.925. The reactor is purged several times with hydrogen and then pressurized to 1 atmosphere-65 sphere with hydrogen. External cooling is applied in order to avoid that the reactor contents become warmer than 35 ° C. during the exothermic first stage of the reduction. The first stage is finished after 15 minutes when fresh catalyst

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is used, or in 30 minutes if 4 times recycled catalyst is used.

The second stage of the reduction of the N-oxybenzotriazole to the desired 2-arvl-2H-benzotriazoI is carried out at 50 ° C. This stage is not very exothermic. A little warming from the outside is necessary. The second stage is complete after a further 30 minutes if fresh catalyst is used, after 60 minutes in the case of 4 times recycled catalyst.

As soon as hydrogen absorption ceases and the reaction is complete, the remaining hydrogen is released from the reactor and a nitrogen atmosphere is created.

The reactor contents are filtered under nitrogen to remove the dispersed palladium on carbon catalyst. The separated catalyst is washed on the filter with toluene and is then ready to be recycled into the hydrogenation process where it can be used many more cycles with minimal loss of activity.

The combined alkaline organic solutions of the desired product are concentrated by distillation under vacuum and give as distillates toluene-methanol, toluene-diethylamine and finally toluene-water. The water can be removed from the latter. The solvents obtained can be used in another hydrogenation reaction. The still hot residue contains the crude product in a yield of 80% of theory. The crude product contains some amine by-product that can be removed by acid extraction.

The crude product is purified by dissolving 8.0 g of crude product in 11.0 g of toluene. This solution is extracted with 8.0 g of 70% aqueous sulfuric acid. The toluene solution is then stirred with 0.8 g Prolit-Rapid, an acid clay, and filtered. The clay is washed with 3.0 g of toluene. The combined toluene filtrate is concentrated by vacuum distillation. After 9.0 g of toluene are separated, 6.5 g of isopropanol are added dropwise to the distillation residue. The solution obtained is cooled to 0-5 ° C. The crystals obtained are filtered off, washed with 4.0 g of cold isopropanol and dried at 70-80 ° C. in vacuo; Yields of pure product 7.6 g (75% of theory based on the original azobenzene intermediate).

Example 2

2 ~ (2-Hydroxy-5-methylphenyl) -2H-benzotriazole

According to Example 1, a hydrogen pressure of 3.3-2 atmospheres is used instead of 1 atmosphere. The reaction temperature is kept at 58-60 ° C instead of 35 ° C in the first stage and 50 ° C in the second stage. 3% (weight) 5% palladium on activated carbon catalyst are used instead of 7.5% (weight), based on the azobenzene intermediate. The reaction time for the total absorption of hydrogen is 125 minutes. The yield of crude product is almost the same, 75% of theory.

In example 2, if the hydrogen pressure is 1 atmosphere, the reaction time is extended to 250 minutes, but the yield of crude product was the same (75% of theory).

If the diethylamine component of the organic solvent system is omitted in Example 2, the complete absorption of hydrogen takes place in 60 minutes, but the desired product is not obtained. The presence of the organic base, such as diethylamine, is necessary to give the desired 2-aryl-2H-benzotriazole upon reduction of the corresponding o-nitroazobenzenes.

Example 3

2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole

In Example 2, if the 5% palladium on activated carbon catalyst is replaced by an equivalent amount of 5% platinum on activated carbon catalyst and the reaction is carried out at 58-78 ° C., the reaction time for the complete absorption of the hydrogen is 50 minutes, the yield of raw desired product 55%.

Platinum is a suitable catalyst for this hydrogenation, but is less selective than palladium and gives more undesirable by-products.

In Example 3, if the diethylamine is omitted from the organic solvent system, the hydrogen absorption is complete after 40 minutes, but no desired product has been obtained. It is therefore imperative that the organic solvent system contain a base, such as an organic amine, to form 2-aryl-2H-benzotriazoles.

Example 4

2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole

If the 5% palladium on activated carbon catalyst is replaced in Example 2 by an equivalent amount of 5% rhodium on activated carbon catalyst, the desired crude product is obtained.

If the diethylamine is omitted from the organic solvent system in Example 4, complete hydrogen absorption is achieved in 90 minutes, but no desired product is obtained.

As with palladium and platinum catalysts, no product was obtained with rhodium on activated carbon catalyst if a base such as diethylamine is missing in the organic solvent system.

Example 5

2- (2-hydroxy-3,5-di-tert-amylphenyl) -2H-benzotriazole

According to the general procedure of Example 1, an equivalent amount of 2-nitro-2'-hydroxy-3 ', 5'-di-tert-amylazo-benzene is used instead of 2-nitro-2 "-hydroxy-5'-methylazo-benzene The above product is obtained in yields of 52-67% based on the intermediate azobenzene that was originally used. The reaction is carried out in a 23.3% (weight) solution of the azobenzene in isopropanol at 1-3% (weight ) Catalyst and carried out with 1.1 - 2.0 moles of diethylamine per mole of azobenzene intermediate.

The effect of the amount of water-miscible organic amine on the yield of 2-aryl-2H-benzotriazole can be seen from Table A. At least 1.1 moles of organic amine per mole of o-nitroazobenzene are necessary to achieve good yields of the desired product. If more than 1.5 moles of organic amine are used per mole of o-nitroazobenzene intermediate, this does not further increase the yield.

TABLE A

Effect of the amount of diethylamine on the yield

2- (2-hydroxy-3,5-di-tert-amylphenyl) -2H-benzotriazole

Hydrogen% of theory

Equivalents of amine to o-nitroazobenzene

% Yield of 2-ary] -2H-benzotriazole

143

0.1

24.7

155

1.1

55.0

154

1.5

49.5

156

2.0

50.0

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

9

615427

Reaction conditions:

- 23.3% (weight) solution of the corresponding o-nitro-azobenzene intermediate in isopropanol

- atmospheric pressure -

- temperature 55 - 60 ° C 5

- Catalyst 5% palladium on activated carbon, used in 3% (weight) based on o-nitroazobenzene intermediate.

Table B shows the effect of other variables on the yield of 2- (2-hydroxy-3,5-di-tertamylphenyl) -2H-benzotriazole, produced by reductive cyclization of 23.3% (weight ) Solution of the corresponding o-nitro-azobenzene intermediate in isopropanol with 5% palladium catalyst on different supports, with different concentrations of catalyst and different temperatures in the presence of 2 moles of diethylamine per o-nitro-azobenzene intermediate, at atmospheric pressure .

TABLE B

Temperature% on substrate IHSEXS6 "ÄSf ^ ylSbenzo-

GradC Pd! Lgfla £ AZ ° -Twl '% of theory triazole product

60

coal

1

152

52

60

coal

2nd

142

62

45

Alumina

1

134

67

45

coal

1

142

57

45

asbestos

2nd

83

Ended at

N-oxy

45 coal 2 134 64

The yields of 2-aryl-2H-benzotriazoI vary from 52 - 67Té. The results are particularly favorable at low temperature (45 ° C. compared to 60 ° C.), higher concentration of catalyst (2 c / c compared to 19 c) and use of aluminum oxide instead of carbon as a support for the palladium catalyst. In all batches, the products contained some Z-amino ^ '- hydroxy-S' ^ '- di-tert-amylhydrazobenzene as an undesirable by-product and the yields were somewhat lower (52-67%) with this special 2-aryl-2H-benzo -triazole compared to the yields of 75-85% for 2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole.

Example 6

2- (2-hydroxy-5-tert-octylphenyl) -2H-benzotriazole

According to Example 1, an equivalent amount of 2-nitro-2'-hydroxy-5'-tert-octylazobenzene is used instead of 2-nitro-2'-hydroxy-5'-methylazobenzene and the above product is obtained.

Example 7

5-chloro-2- (2-hydroxy-3,5-di-tert-butylphenyl) -2H-benzotriazole

In Example 5, 2-nitro-2'-hydroxy-3 ', 5'-di-tert-amyl-azobenzene is replaced by an equivalent amount of 2-nitro-5-chloro-2' - hydroxy-3 ', 5'- di-tert-butylazobenzene is replaced, and 5% palladium on activated carbon catalyst is replaced by an equivalent amount of 5% rhodium on activated carbon, and the above product is obtained.

If 5% palladium on activated carbon catalyst is used, the product obtained is the deschloro compound

40 2- (2-Hydroxy-3,5-di-tert-butylphenyl) -2H-benzotriazole.

Example 8

5-chloro-2- (2-hydroxy-3-tert-butyl-5-methylphenyl-2H - benzotriazole

45

In Example 5, 2-nitro-2'-hydroxy-3 ', 5'-di-tert-amyl-azobenzene is replaced by an equivalent amount of 2-nitro-5-chloro-2' - hydroxy-3'-tert-butyl -5'-methylazobenzene and the 5% palladium on activated carbon catalyst by an equal amount

50 5% rhodium on activated carbon catalyst replaced, you get the above product.

Example 9

55 2- (2-Hydroxy-3,5-di-tert-butylphenyl) -2H-benzotriazole

According to Example 5, a 23% (weight) suspension of 2-nitro-2'-hydroxy-3 ', 5'-di-tert-butylazobenzene in isopropanol / triethylamine (1 / 0.18) at 45 ° C. and 1 Atmosphere hydrogenated for 3 hours in the presence of 3% of a 5% palladium on activated carbon catalyst. The above product is obtained in a yield of 77%.

Example 10

65 2- (2-Hydroxy-5-methylphenyl) -2H-benzotriazole

According to Example 1, the organic solvent toluene is replaced by a trialkyl phosphate and the above product is obtained in good yield.

615427

10th

A suspension of 23.3 g of 2-nitro-2'-hydroxy-5'-methyl-azobenzene in 80 g of tributyl phosphate, 20 g of methanol and 8 g of diethylamine with 1.5 g of 5% palladium on activated carbon catalyst is added 1 atmosphere hydrogenated for 55 minutes at a maximum temperature of 55 ° C. The above product with a melting point of 129-130 ° C. is obtained in yields of 80%.

If the tri-butyl phosphate is replaced by the same amount of triethyl phosphate above and no methanol is present, the above product (mp 128-130 ° C.) is obtained in 76% yield.

Example 11

2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole

If in example 1 the toluene, methanol and diethylamine 5 organic solvents are replaced by a comparable weight n-propylamine, the above product is obtained.

Example 12

2- (2-hydroxy-3,5-di-tert-amylphenyl) -2H-benzotriazole

10th

If the isopropanol and diethylamine organic solvent mixture is replaced by a comparable weight of morpholine in Example 5, the above product is obtained.

v

Claims (10)

615427 2. The method according to claim 1, characterized in that one carries out the hydrogenation in an organic solvent or an organic solvent mixture. 2nd PATENT CLAIMS 1. Process for the preparation of 2-aryl-2H-benzotriazo-len of formula I. Oli N (I) wherein R is hydrogen or chlorine, R2 is hydrogen, chlorine, Cj-Q-alkyl, Cj-Cj-alkoxy, C2-C ,, - carboalkoxy, carboxy or -S03H, R3 is C, -C] 2-alkyl, C1-C4-alkoxy, phenyl, phenyl substituted with Ci-Cg-alkyl, Cr, -C6-cycloalkyl, C2-C9-carboalkoxy, chlorine, carboxyethyl or C7-C9-arylalkyl , R4 is hydrogen, C] -C4 alkyl, C1-C4 alkoxy, chlorine or hydroxy, and Rn is hydrogen, Q-C ^ -alkyl, chlorine, C6-Ct; -cycloalkyl or C7-C "-arylalkyl, characterized in that a corresponding o-Ni-troazobenzene with hydrogen at 20 to 100 ° C and 1 to 66 atmospheres mixed with an amine or ammonia in an amount of at least 0.1 mol per mole of o-nitroazo-benzene in the presence of a Hydrogenation catalyst from a noble metal of group VIII of the periodic table or an oxide thereof hydrogenated, wherein, if R "Ro, R3, R4 or R, chlorine, the hydrogenation catalyst is not palladium, and the 2-AryI-2H-benzotriazole isolated. 3. The method according to claim 1, characterized in that the hydrogenation catalyst is palladium, platinum or rhodium. 4. The method according to claim 1, characterized in that the hydrogenation catalyst is palladium. 5. The method according to claim 4, characterized in that the palladium sits on activated carbon or aluminum oxide. 6. The method according to claim 2, characterized in that the organic solvent mixture contains toluene and methanol and the amine is diethylamine. 7. The method according to claim 2, characterized in that the organic solvent is isopropanol, and the amine diethylamine. 8. The method according to claim 1, characterized in that at least 0.9 mol of amine are used per mol of o-nitroazobenzoI intermediate. 9. The method according to claim 1, characterized in that one produces a compound of formula I, wherein R is hydrogen Rj is hydrogen, C, -C2-alkyl, methoxy or carboxy, R i is C1-C12-alkyl, cyclohexyl, phenyl, a-methylbenzyl or carboxyethyl, R4 is hydrogen, hydroxy or methyl, and R is hydrogen, Q-C ^ .- alkyl, cyclohexyl, benzyl or a-methylbenzyl. 10. The method according to claim 4, characterized in that one produces a compound of formula I, wherein R, hydrogen, R2 hydrogen R3 is methyl, sec-butyl, tert-butyl, tert-amyl, tert-octyl, cyclohexyl or carboxyethyl, R4 is hydrogen, and R5 is hydrogen, methyl, tert-butyl, sec-butyl, tert-amyl, tert-octyl or a-methylbenzyl.