JPH0478633B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing 2-allyl-2H-benzotriazole or its N-oxide and derivatives thereof, which are useful as ultraviolet absorbers for various plastic products.

[Prior art] Benzotriazole derivatives are known as ultraviolet absorbers, and are effective in discoloring plastic products such as polyvinyl chloride, unsaturated polyester, polystyene, polyamide, polymethyl tacrylate, cellulose ester, and ABS resin due to ultraviolet light. It is used as an additive to prevent corrosion and deterioration. Therefore, benzotriazole derivatives provided for such uses are required to have excellent color tone and high purity.

As a known method for producing benzotriazole derivatives, US Pat. No. 2,362,988 discloses a method of oxidizing ₀ -aminophenyl azophenol; US Pat. No. 4,041,044 discloses a method of reducing ₀ -nitroazophenols with zinc powder. A process is disclosed; U.S. Pat. No. 4,141,903 discloses the treatment of ₀ -nitroazophenols with hydrogen, carbon monoxide or hydrazine at 20-150°C.
A method for reduction in the presence of a complex catalyst consisting of a copper compound and an amine compound under 1 to 66 atmospheres is disclosed.

On the other hand, U.S. Patent No. 4224451 has the general formula ()
After reducing the ₀ -nitroazophenol to benzotriazole N-oxide in the presence of hydrosulfide or sulfide, this N-oxide is further reduced in the presence of zinc or complex powder to form 2-aryl-
A method for making 2H-benzotriazole derivatives is disclosed. This indicates that although sulfides are suitable for the production of N-oxides, their reducing power is not sufficient for the production of benzotriazole.

In this connection, Aust.J.Chem.1984.37, 2489 describes the reduction of ₀ -nitroazolephenols in ethanol in the presence of sodium diionite to directly prepare 2-aryl-2H-benzotriazole derivatives. A method is disclosed.

However, when sodium dithionite is used as a reducing agent in this way, there is the problem that sodium dithionite decomposes during the reaction and produces colloidal sulfur, and furthermore, the production of colloidal sulfur causes the production of colloidal sulfur. The problem is that approximately five times the theoretical amount of sodium dithionite must be used to compensate for the loss of sodium thionate. Further, there is a problem that the yield and purity of the obtained 2-aryl-2H-benzotriazole derivatives are not constant.

[Problems to be Solved by the Invention] In the above-mentioned conventional techniques, the method using hydrogen, carbon monoxide, hydrazine, etc. has a problem in terms of safety, and the method using only sodium dithionite also has problems with colloidal sulfur. There are problems caused by the generation of

Therefore, an object of the present invention is to solve the above problems and provide a method for producing 2-aryl-2H-benzotriazole and its derivatives with high yield and good color tone.

[Means for Solving the Problems] As a result of research to achieve the above object, the present inventors found that when producing ₂ -aryl-2H-benzotriazole by reducing 0-nitroazophenol, By allowing sodium formate to coexist with sodium thianate, the reduction reaction by sodium dithionite is carried out, and at the same time, the sulfur dioxide generated by the decomposition of sodium dithionite is converted to sodium dithionite by the sodium formate. We found that 2-aryl-2H-benzotriazole can be obtained in high yield even when using a small amount of sodium dithionite as a reducing agent by carrying out a reaction in which 2-aryl-2H-benzotriazole is used as a reducing agent. They also discovered that similar results can be obtained when sodium hydrogen is used, leading to the completion of the present invention.

That is, the present invention is based on the general formula (): (In the formula, R ¹ represents hydrogen or chlorine, R ² _and R ³ represent hydrogen, a lower alkyl group having 1 to 5 carbon atoms, or a phenyl alkyl group having 7 to 9 carbon atoms) General formula () produced by reducing azophenol by heating it to the reflux temperature of the solvent in the presence of sodium dithionite and sodium formate or sodium bisulfite and sodium formate in a solvent: (In the formula, the meanings of R ¹ , R ² and R ³ are the same as above.) 2-Aryl-2H-benzotriazole and derivatives thereof or general formula (): (wherein the meanings of R ¹ , R ² and R ³ are the same as above) The present invention relates to a method for producing a compound represented by () or ().

The meanings of R ¹ , R ² and R ³ in the formula () representing ₀ -nitroazophenol, which is the starting material, are as described above, but here, R ² has 1 to 5 carbon atoms.
and alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, n-
They are amyl group, isoamyl group, sec-amyl group, activated amyl group, and tert-amyl group.

The compound represented by the formula () can be produced, for example, by the method described in US Pat. No. 3,773,751.

The compound represented by formula () or formula () can be obtained by reducing the compound represented by formula () above under predetermined conditions.

The solvent used in the present invention includes water, N,N'-
Dimethylformamide, toluene, chlorobenzene, benzene, xylene, ligroin, etc. can be mentioned, and one type of these can be used, or two or more types can be used as a mixture. Here, when a mixed solvent of water and a water-insoluble solvent is used as the solvent, the reaction will be carried out in a two-phase state.

Sodium dithionite or sodium hydrogen sulfite used in the present invention acts as a reducing agent, and sodium formate reduces the sulfur oxide produced by the decomposition of sodium dithionite or sodium hydrogen sulfite during the reduction reaction. It works by being converted into sodium dithionate or sodium bisulfite.

The amounts of sodium dithionite and sodium formate to be used are 1.12 to 4 times the amount of sodium dithionite and 3 to 4.5 times the amount of sodium formate per 1 mole of the compound represented by formula (). Use. The amounts used when using sodium bisulfite and sodium formate are also similar. Sodium dithionite or sodium bisulfite and sodium formate can be used at once or in parts.

In the present invention, a base such as sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, etc. can be allowed to coexist in the reaction system if necessary. As a phase transfer catalyst, for example, a quinone such as sodium 2-anthraquinone sulfone or 1,4
- It is preferable to coexist a mixture of naphthoquinone and sodium p-toluenesulfonate in the reaction system because the reduction reaction can proceed more efficiently.

The reduction reaction is carried out by dissolving the compound represented by formula () in the above solvent and then heating it to the reflux temperature of the solvent. The heating temperature varies depending on the solvent used, but is usually 80°C or higher, preferably in the range of 100 to 104°C. Further, the reaction time is usually within 4 hours.

There is no need to particularly adjust the pH of the reaction solution, but it is 9.5.
The range is preferably from 10 to 10, and the reaction is preferably carried out under a nitrogen atmosphere.

The method for separating the target compound represented by formula () or formula () from the reaction solution depends on whether the solubility used is a single solvent or a mixed solution of water and a water-insoluble solvent. different. An example is given below.

In the case of a single solvent, first, a solvent such as isopropanol is added to the reaction solution to reduce the solubility of the product, and then heated at a high temperature and filtered while still hot to dissolve the product, which is mainly composed of sodium sulfate and sodium sulfite. Remove impurities that have been after that,
Cool the liquid to about 5℃ and use formula () or formula ()
After precipitating crystals of a compound that can be represented by:

When performing a two-phase reaction using water and toluene as solvents, for example, separate the aqueous layer from the reaction solution, distill and concentrate the remaining toluene solution as necessary, and then add a solvent such as isopropanol. However, the compound represented by formula () or () can be obtained in the same manner as when using a single solvent.

Here, the compound represented by the formula () is the compound represented by the formula ()
It is an intermediate obtained in the process of reducing the compound represented by formula () to produce the compound represented by formula (). Therefore, by interrupting the progress of the reduction reaction at an appropriate stage during the reaction, the compound represented by the formula () can be obtained, and by completing the reduction reaction without interrupting the reaction, the compound represented by the formula ( )
A compound represented by can be obtained. That is, after producing the compound represented by formula (),
By reducing this, a compound represented by formula () can be obtained. The progress of the reduction reaction is
It can be easily confirmed by thin layer chromatography (developing solvent: n-hexane: ethyl acetate = 4:1), and the product can be confirmed by infrared absorption spectroscopy to confirm the change in the nitro group in general formula (). This is possible.

The compound represented by () thus obtained is almost white, and the compound represented by formula () is slightly pale yellow.

[Example] Production of 5-chloro-2-(2'-hydroxy-3',5'-di-tert-butylphenyl)2H benzotriazole First, a 100 ml three-necked flask was equipped with a stirrer, a reflux condenser, and nitrogen injection. The device was attached. DMF here
(12 ml), 2-nitro-4-chloro-2'-hydroxy-3',5'-di-tert-butylazobenzene (3.89 g, 10 mmol), sodium formate (2.53
g, 37.2 mmol) and sodium dithionite (2 g, 11.5 mmol) were added. Under a nitrogen atmosphere, start stirring and heat until reflux begins.
The reaction was continued at 100-105°C for an additional hour. After this sodium dithionite (1 g, 5.7 mmol)
was added and the reaction was continued at 100-105°C for an additional 1.5 hours. Then isopropyl alcohol (40ml)
After heating at 80-85℃ and maintaining for 20 minutes,
I was in a hot state. The white solid, consisting primarily of sodium sulfate, was discarded. The filtered mother liquor was heated to 5°C.
The precipitate formed is further evaporated and washed with a minimum amount of isopropyl alcohol.
The desired benzotriazole, almost white in color, was obtained (2.10 g). Further, the remaining mother liquor was distilled under reduced pressure to remove the solvent, and the residue was recrystallized from 10 ml of isopropyl alcohol to obtain an additional 0.9 g of the desired benzotriazole. Total yield (84% of theory): mp 153.5-155.5°C.

Example 2 2-(2'-hydroxy-5'methylphenyl)-2H
-Production of benzotriazole First, a stirrer, a reflux condenser, and a nitrogen injection device were attached to a 100 ml three-necked flask. DMF for this
(10 ml), 2-nitro-2'-hydroxy-5'-methylazobenzene (2.57 g, 10 mmol), sodium formate (3.00 g, 44 mmol) and sodium bisulfite (3.57 g, 34 mmol) were added.
Stirring was started under a nitrogen atmosphere, heating was continued until reflux started, and the reaction was continued at 100-105° C. for one hour. Next, isopropyl alcohol (20 ml) was added and treated in the same manner as in Example 1 to obtain an almost white benzotriazole.

Total yield (74.2% of theory): mp 129-130°C.

Example 3 Production of 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)-2H-benzotriazole First, a 100 ml three-necked flask was equipped with a stirrer, a reflux condenser, and a nitrogen injection device. I let it happen. DMF for this
(10ml), 2-nitro-2'-hydroxy-3',5'-
Di-tert-amyl azobenzene (3.83 g, 10 mmol) Sodium formate (2.53 g, 37 mmol) and Sodium bisulfite (3.24 g, 31 mmol)
was added. Begin stirring under nitrogen atmosphere and heat until reflux begins, then heat at 10 to 105 °C for another hour.
The reaction was carried out at ℃. Next, isopropyl alcohol (35 ml) was added and the mixture was treated in the same manner as in Example 1 to obtain the desired benzotriazole, which was almost white in color.
Total yield (80.9% of theory): mp 80-81°C.

Example 4 Production of 2-(2′-hydroxy-3′,5′-di(1″,1″dimethylbenzyl)phenyl)-2H-benzotriazole First, place a 100 ml three-necked flask with a stirrer and a reflux condenser. and a nitrogen injection device was attached. DMF for this
(5 ml), 2-nitro-(2'-hydroxy-3',5'
Di(a,a-dimethylbenzyl)phenyl)azobenzene (2.4 g, 5 mmol), sodium formate (1.5 g, 22.0 mmol) and sodium bisulfite (1.5 g, 14 mmol) were added. Start stirring under nitrogen atmosphere and heat until reflux begins.
The reaction was allowed to proceed for an additional hour at 100-105°C. Next, isopropyl alcohol (20 ml) was added and treated in the same manner as in Example 1 to obtain the desired benzotriazole, which was almost white in color. Total yield (theoretical value of 55.4
%): Melting point 138-138.5℃.

Example 5 Production of 5-chloro-2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-2H-benzotriazole First, a 100 ml three-necked flask was equipped with a stirrer, a reflux condenser, and nitrogen. An injection device was attached. DMF for this
(6 ml), chlorobenzene (4 ml), 2-nitro-
4-chloro-2'-hydroxy-3',5'-di-tert
-butylazobenzene (3.89 g, 10 mmol),
Sodium formate (3.0 g, 44 mmol) and sodium bisulfite (3.5 g, 33.7 mmol) were added. Stirring was started under a nitrogen atmosphere, heating was continued until reflux began, and the reaction was continued at 100 to 105°C for an additional hour and a half.

Next, isopropyl alcohol (50 ml) was added and treated in the same manner as in Example 1 to obtain the desired benzotriazole. Total yield (75% of theory).

Example 6 Production of 5-chloro-2-(2'-bitroxy-3',5'-di-tert-butylphenyl)-2H-benzotriazole First, place a stirrer, a reflux condenser, and nitrogen into a 100 ml three-necked flask. An injection device was attached. DMF for this
(6 ml), toluene (4 ml), 2-nitro-4-chloro-2'-hydroxy-3',5'-di-tert-butylazobenzene (3.89 g, 10 mmol), sodium formate (3.09 g, 44 mmol). ) and sodium bisulfite (3.5 g, 34 mmol) were added.

Stirring was started under a nitrogen atmosphere and heating was continued until reflux began, and the reaction was continued at 100 to 105°C for an additional hour and a half. Then isopropyl alcohol (50ml)
The desired benzotriazole was obtained by processing in the same manner as in Example 1 in which . Total yield (theoretical 75
%).

Example 7 2-(2'-hydroxy-5'-methylphenyl)-
Production of 2H-benzotriazole-N-oxyto First, a 250 ml three-necked flask was equipped with a stirrer, a reflux condenser, and a nitrogen injection device. 100ml of this
of water, sodium hydroxide (1.5 g), 2-nitro-
2'-Hydroxy-5'-methyl-azobenzene (2.57 g, 10 mmol) and sodium formate (3.00 g, 44 mmol) were added. Start stirring under a nitrogen atmosphere and heat to 70-75°C, and then add an aqueous solution of sodium dithionite (2.2 g, 12.6 mmol) dissolved in 20 ml of water so that the dithionite ions are not present in excess. It was added little by little as needed. At the time of this addition, one drop of a 25% aqueous solution of paraquat was added at the beginning, and after the blue color produced by the reaction between paraquat and dithionite ions disappeared, it was added little by little. The additional time was approximately 3.5 hours. The reaction was continued for an additional 30 minutes.
Next, the reaction product was cooled to 50°C, and the resulting solution was acidified with 5 ml of agricultural hydrochloric acid. N-oxide was obtained. Further, 13 ml of isopropyl alcohol was added to the mother liquor and recrystallized to obtain 1.8 g of pale yellow crystals of the desired benzotriazole-N-oxide. Yield (74.7% of theory): melting point 138−
139℃.

Example 8 2-(2'-hydroxy-5'-methylphenyl)-
Production of 2H-benzotriazole First, a 250 ml three-necked flask was equipped with a stirrer, a reflux condenser, and a nitrogen injection device. 100ml of this
of water, sodium hydroxide (1.5 g), 2-nitro-
2'-Hydroxy-5'-methyl-azobenzene (2.57 g, 10 mmol) and sodium formate (3.00
g, 44 mmol) was added and stirring was started under a nitrogen atmosphere and heated to 70-75°C. Next, an aqueous solution of sodium dithionite (6.68 g, 38 mmol) dissolved in 60 ml of water was added over 11 hours in the same manner as in Example 4, and the reaction was continued for an additional hour. The reaction mixture was then cooled to room temperature and the precipitate formed was filtered off. The filtered solution was extracted three times with 10 ml of chloroform, and then the solution was removed under low pressure to obtain 12 ml of the residue.
Recrystallize with isopropyl alcohol to give 1.6g
The desired triazole was obtained. Yield (71% of theory) Example 9 Production of 6-chloro-2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-2H-benzotriazole-1-oxide First, 100 ml A three-necked flask was equipped with a stirrer, a reflux condenser, and a nitrogen injection device. To this was added water (30 ml), 2-nitro-4-chloro-2'-hydroxy-3',5'-tert-butylazobenzene (3.89 g,
10 mmol), sodium hydroxide (5.2 g), chlorobenzene (20 ml), sodium formate (2.04 g,
30 mmol), sodium p-toluenesulfonate (3.0 g) and 1,4 naphthoquinone (0.2 g). Stirring was started under a nitrogen atmosphere and heated (95-100°C) until reflux began. Next, an aqueous solution of sodium dithionite (3.6 g, 20 mmol dissolved in 20 ml of water) was added as evenly as possible over a period of 4 hours, followed by a further 3 minutes of reaction at 100-105°C. Then, after cooling to room temperature,
The aqueous layer was separated and removed, and the remaining organic layer was washed twice with 30 ml of water. The solvent is then recovered by distillation under reduced pressure,
The residue was crystallized from 40 ml of isopropyl alcohol to give 3.55 g of the desired benzotriazole 1-
Obtained oxide. Yield (95.2% of theory): Melting point
190−192℃.

Example 9 Production of 6-chloro-2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-2H-benzotriazole-1-oxide First, place a stirrer in a 100 ml three-necked flask and reflux. A cooler and nitrogen injection system were attached. To this was added water (30 ml), 2-nitro-4-chloro-2'-hydroxy-3',5'-di-tert-butylazobenzene (8.89 g, 10 mmol), sodium hydroxide (5.1
g), chlorobenzene (20ml), sodium formate (2.04g, 30mmol) and sodium 2-anthraquinonesulfonate (0.02g) were added. Stirring was started under a nitrogen atmosphere and heated (95-100°C) until reflux began. An aqueous solution of sodium dithionite (3.4 g, 19.5 mmol dissolved in 20 ml of water) was added as evenly as possible over a period of 4 hours, after which the reaction was continued for an additional 30 minutes at 95-100°C. Thereafter, after cooling to room temperature, the aqueous layer was separated and removed, and the remaining organic layer was washed twice with 30 ml of water. Collect the solvent by distillation under reduced pressure and collect 40ml of the residue.
to crystallize it with isopropyl alcohol.
3.6 g of the desired benzotriazole-1-oxide was obtained. Yield (96.5% of theory) Example 11 Production of 5-chloro-2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-2H-benzotriazole First, a 100 ml three-necked flask was fitted with a stirrer, reflux condenser and nitrogen injection device. to this
DMF (6 ml), chlorobenzene (4 ml), 5-chloro-2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-2H-benzotriazole-N-
Oxide (2.39 g, 6.4 mmol), sodium carbonate (5.5 g), sodium formate (2.10 g, 3 mmol) and sodium bisulfite (2.03 g, 20 mmol) were added. Stirring was started under a nitrogen atmosphere and heated (100-105°C) until reflux began. After the reaction was continued at this temperature for 1.5 hours, 50 ml of isopropyl alcohol was added and the mixture was treated as in Example 1 to obtain 1.49 g of the desired benzotriazole. Yield (65.1% of theoretical value) [Effect of the invention] According to the present invention, 2-aryl-2H-benzotriazole and its N-
Oxides or derivatives thereof can be obtained. Furthermore, by using sodium formate, the amount of reducing agent used can be significantly reduced.

Claims (1)

[Claims] 1 General formula (): (In the formula, R ¹ represents hydrogen or chlorine, R ² and R ³ represent hydrogen, a lower alkyl group having 1 to 5 carbon atoms, or a phenyl alkyl group having 7 to 9 carbon atoms) General formula () produced by reducing azophenol by heating it to the reflux temperature of the solvent in the presence of sodium dithionite and sodium formate or sodium bisulfite and sodium formate in a solvent: (In the formula, the meanings of R ¹ , R ² and R ³ are the same as above.) 2-Aryl-2H-benzotriazole and derivatives thereof or general formula (): (wherein the meanings of R ¹ , R ² and R ³ are the same as above) A method for producing a compound represented by formula () or (). 2 The solvent is water, N,N'-dimethylformamide,
The manufacturing method according to claim 1, wherein at least one kind is selected from the group consisting of toluene and chlorobenzene. 3. The manufacturing method according to claim 1, wherein sodium 2-anthraquinonesulfonate or a mixture of 1,4-naphthoquinone and sodium p-toluenesulfonate is present in the solvent.