CA1154778A - Process for the production of 2-aryl-2h- benzotriazoles - Google Patents
Process for the production of 2-aryl-2h- benzotriazolesInfo
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- CA1154778A CA1154778A CA000250324A CA250324A CA1154778A CA 1154778 A CA1154778 A CA 1154778A CA 000250324 A CA000250324 A CA 000250324A CA 250324 A CA250324 A CA 250324A CA 1154778 A CA1154778 A CA 1154778A
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- carbon atoms
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Abstract
PROCESS FOR THE PRODUCTION OF
Abstract of the Disclosure A process for the production of 2-aryl-2H-benzotriazoles comprises re-ducing and cyclizing the corresponding o-nitroazobenzenes with hydrogen at a temperature in the range of about 20°C to about 100°C and at a pressure in the range of about 1 atmosphere to about 66 atmospheres in an aqueous alkaline medium at a pH over 10 in the presence of a noble metal hydrogenation catalyst, preferably palladium. High yields of pure product are obtained with a concomit-ant reduction of undesired by-product and a reduction in effluent pollution pro-blems.
Abstract of the Disclosure A process for the production of 2-aryl-2H-benzotriazoles comprises re-ducing and cyclizing the corresponding o-nitroazobenzenes with hydrogen at a temperature in the range of about 20°C to about 100°C and at a pressure in the range of about 1 atmosphere to about 66 atmospheres in an aqueous alkaline medium at a pH over 10 in the presence of a noble metal hydrogenation catalyst, preferably palladium. High yields of pure product are obtained with a concomit-ant reduction of undesired by-product and a reduction in effluent pollution pro-blems.
Description
7 ~ 13 This invention pertains -to a process i-or the prepara-tion of 2-aryl-2H-benzotriazoles and derivatives thereof. More particularly, the invention relates to a nove:L process for pre-paring 2-aryl-2H-benzotriazoles whereby high yields of the desired products are obtained and effluent pollution problems occurring with present processes for making such products are essentially eliminated.
Heretofore, the conversion of an ortho-nitroazobenzene to the corresponding 2-aryl-2H-benzotriazole has been accom-plished by chemical and electrolytic reduction processes. For example, as seen in U.S. Patents 3,072,585 and 3,230,194 o-nitroazobenzene derivatives have been chemically reduced utilizing zinc in alcoholic sodium hydroxide solutions to give good yields of the corresponding 2-aryl-2H-benzotriazoles.
Ammonium sulfide, alkali sulfides, zinc with ammonia at go-loooc,sodiumhydrosulfide and zinc with hydrochloric acid have also been used as the chemical reducing agents for this transormation as disclosed in U.S. Pa-tent 2,362,988. The use of ammonium sulfied was also reported by S.N. Chakrabarty et al.
J. Indian Chem. Soc., 5, 555 (1928); Chem. Abst., 23, 836, (1929) with mixed results depending on the presence or absence of substituent groups on the 2-aryl group. In some cases the desired 2-aryl-2H-benzotriazoles were not formed at all with the products of reduction being only the corresponding o-aminoazobenzenes.
~' ~ 77~3 Electrolytic reduction of o-nitroazobenzenes was reported by H. Itomi, Mem. Coll. Sci. Kyoto Imp. Univ., 12A, No. 6, 343 (1929); Chem. Abst., 24, 2060 (1930) with the use of a copper cathode in dilute sodium hydroxide solution.
Yields varied from 25 to 60% depending on specific embodiments and conditions with a major impurity being formed, namely the corresponding o-aminoazobenzene.
The widely used zinc dust and sodium hydroxide chemical reducing system for transforming o-nitroazobenzenes into the corresponding 2-aryl-2H-benzotriazoles was reported by K. Elbs, et al, J. Prakt. Chem., 108, 204 (1924); Chem.
Abst., 19, 514 (1925). The yields of the desired 2-aryl-2H-benzotxiazoles varied from 30 to 85% depending on the specific o-nitroazobenzene intermediate reduced.
The known chemical and electrolytic reduction pro~
cesses for preparing 2-aryl-2H-benzotriazoles are not practi-cal or economically attractive in many cases. The widely used zinc dust and sodium hydroxide system produces effluent pollution problems in respect to waste disposal of zinc sludge which is of increasing environmental concern.
The preparation in good yield of the isomeric, but chemically distinct lH-benzotriazoles by the catalytic reduc-tion in alkaline medium of o-nitrophenylhydrazine and selected pheynl ring substituted alkyl and perfluoroalkyl r :
':
7~3 derivatives thereof was reported in Japanese patent publication, Sho 48-26012, August 3, 1973. The isomeric 2H-benzotriazoles of this invention cannot be prepared from phenylhydrazines.
It is therefore an object of this invention to provide a novel process for the preparation of 2-aryl-2H-benzotriazoles avo~iding severe pollution and environmental problems.
A further object of this invention is to prepare 2-aryl-2H-benzotriazoles by reducing and cyclizing the corresponding o-nitroazobenzene under certain conditions hereinafter set forth in greaterdetailwhereby high yields of the products can be obtained in acceptable purity.
According to the present invention, there is provided a process for the production of 2-aryl-2H-benzotriazoles of the formula I
Rl ~ ~ N / ~ 5 wherein Rl is hydrogen or chlorine, R2 is hydrogen, chlorine, lower alkyl of 1 to 4 carbon atoms, lower alkoxy of l to 4 carbon atoms, carboalkoxy of 2 to 9 carbon atoms, carboxy or -S03H, R3 is alkyl of 1 to 12 carbon atoms, alkoxy of 1 to 4 carbon atoms, phenyl, phenyl substituted wil~h alkyl groups, said alkyl groups having 1 to 8 carbon atoms, cycloalkyl of !, to 6 carbon atoms, carboalkoxy of 2 to 9 carbon atoms, chlorine carboxy ethyl or aryl alkyl of 7 to 9 carbon atoms, R4 is hydrogen, lower alkyl of l to 4 carbon atoms, lower alkoxy of 1 to 4 carbon atoms, chlorine or hydroxyl and R5 is hydrogen, alkyl of 1 to 12 carbon atoms, chlorine, cycloaklyl of 5 to 6 carbon atoms or arylalkyl of 7 to 9.carbon atoms, which comprises reducing and cyclizing the corresponding o-nitroazobenzene with hydrogen at a temperature in the range of from about 20C to about lOO~C and at a pressure .~
~4~71!3 in the range of from about 15 psig (1.05 kg/cm2, 1 atmosphere) to about 1000 psig ~70 kg/cm2, 66 atmospheres) while mixed in an aqueous alkaline medium having a pH greater than lO in the presence of a hydrogenation catalyst selected from the group consisting of the noble metals of Group VIII
of the Periodic Table with the proviso that, when Rl, R2, R3, R4 or R5 is chlorine, the hydrogenati~n catalyst cannot be palladium, and recovering the desired 2-aryl-2H-benzotriazole.
Taken in its broadest aspect~ one embodiment of the present invention provides a process for the production of 2-~2-hydroxy-5-methylphenyl)-2H-benzotriazole which comprises reducing and cyclizing 2-nitro-2'-hydroxy-5'-methylazobenzene with hydrogen at reducing conditions in an aqueous alkaline medium in the presence of a hydrogenation catalyst selected from the group consisting of the noble metals of group VIII of the Periodic Table, and recovering the desired 2-~2-hydroxy-5-methyl)-2H-benzotriazole.
A further embodiment of this invention is found in a process for the production of 2-~2-hydroxy-5-methyl--4a-~; `
~4~7 ~8 `phenyl)-2H-benzotriazole which comprises treating 2-nitro-2'-hydroxy-5'-methylazobenzene with hydrogen at a temperature in the range of from about 20C to about 100C and at a pressure in the range of about 1 atmosphere to about 66 atmo6pheres in an aqueous alkaline medium in the presence of a hydrogenation catalyst comprising a noble metal of Group VIl of the Periodic Table, removing the noble metal catalyst by filra-tion, lowering the pH of the aqueous system to a value less than 10 to precipitate the desired product, and recovering the desired 2-(2-hydroxy-5-methylphenyl3-2H-benzotriazole by conventional procedures.
The process of this invention can be carried out at a temperature in the range of from about 20C to about 100C, preferably from about 30C to 80C, and most preferably from about 40C to about 70C.
A specific embodiment of the invention is exemplified in a process for the production of 2-(2-hydroxy-5-methyl phenyl)-2H-benzotriazole, which comprises treating 2-nitro-
Heretofore, the conversion of an ortho-nitroazobenzene to the corresponding 2-aryl-2H-benzotriazole has been accom-plished by chemical and electrolytic reduction processes. For example, as seen in U.S. Patents 3,072,585 and 3,230,194 o-nitroazobenzene derivatives have been chemically reduced utilizing zinc in alcoholic sodium hydroxide solutions to give good yields of the corresponding 2-aryl-2H-benzotriazoles.
Ammonium sulfide, alkali sulfides, zinc with ammonia at go-loooc,sodiumhydrosulfide and zinc with hydrochloric acid have also been used as the chemical reducing agents for this transormation as disclosed in U.S. Pa-tent 2,362,988. The use of ammonium sulfied was also reported by S.N. Chakrabarty et al.
J. Indian Chem. Soc., 5, 555 (1928); Chem. Abst., 23, 836, (1929) with mixed results depending on the presence or absence of substituent groups on the 2-aryl group. In some cases the desired 2-aryl-2H-benzotriazoles were not formed at all with the products of reduction being only the corresponding o-aminoazobenzenes.
~' ~ 77~3 Electrolytic reduction of o-nitroazobenzenes was reported by H. Itomi, Mem. Coll. Sci. Kyoto Imp. Univ., 12A, No. 6, 343 (1929); Chem. Abst., 24, 2060 (1930) with the use of a copper cathode in dilute sodium hydroxide solution.
Yields varied from 25 to 60% depending on specific embodiments and conditions with a major impurity being formed, namely the corresponding o-aminoazobenzene.
The widely used zinc dust and sodium hydroxide chemical reducing system for transforming o-nitroazobenzenes into the corresponding 2-aryl-2H-benzotriazoles was reported by K. Elbs, et al, J. Prakt. Chem., 108, 204 (1924); Chem.
Abst., 19, 514 (1925). The yields of the desired 2-aryl-2H-benzotxiazoles varied from 30 to 85% depending on the specific o-nitroazobenzene intermediate reduced.
The known chemical and electrolytic reduction pro~
cesses for preparing 2-aryl-2H-benzotriazoles are not practi-cal or economically attractive in many cases. The widely used zinc dust and sodium hydroxide system produces effluent pollution problems in respect to waste disposal of zinc sludge which is of increasing environmental concern.
The preparation in good yield of the isomeric, but chemically distinct lH-benzotriazoles by the catalytic reduc-tion in alkaline medium of o-nitrophenylhydrazine and selected pheynl ring substituted alkyl and perfluoroalkyl r :
':
7~3 derivatives thereof was reported in Japanese patent publication, Sho 48-26012, August 3, 1973. The isomeric 2H-benzotriazoles of this invention cannot be prepared from phenylhydrazines.
It is therefore an object of this invention to provide a novel process for the preparation of 2-aryl-2H-benzotriazoles avo~iding severe pollution and environmental problems.
A further object of this invention is to prepare 2-aryl-2H-benzotriazoles by reducing and cyclizing the corresponding o-nitroazobenzene under certain conditions hereinafter set forth in greaterdetailwhereby high yields of the products can be obtained in acceptable purity.
According to the present invention, there is provided a process for the production of 2-aryl-2H-benzotriazoles of the formula I
Rl ~ ~ N / ~ 5 wherein Rl is hydrogen or chlorine, R2 is hydrogen, chlorine, lower alkyl of 1 to 4 carbon atoms, lower alkoxy of l to 4 carbon atoms, carboalkoxy of 2 to 9 carbon atoms, carboxy or -S03H, R3 is alkyl of 1 to 12 carbon atoms, alkoxy of 1 to 4 carbon atoms, phenyl, phenyl substituted wil~h alkyl groups, said alkyl groups having 1 to 8 carbon atoms, cycloalkyl of !, to 6 carbon atoms, carboalkoxy of 2 to 9 carbon atoms, chlorine carboxy ethyl or aryl alkyl of 7 to 9 carbon atoms, R4 is hydrogen, lower alkyl of l to 4 carbon atoms, lower alkoxy of 1 to 4 carbon atoms, chlorine or hydroxyl and R5 is hydrogen, alkyl of 1 to 12 carbon atoms, chlorine, cycloaklyl of 5 to 6 carbon atoms or arylalkyl of 7 to 9.carbon atoms, which comprises reducing and cyclizing the corresponding o-nitroazobenzene with hydrogen at a temperature in the range of from about 20C to about lOO~C and at a pressure .~
~4~71!3 in the range of from about 15 psig (1.05 kg/cm2, 1 atmosphere) to about 1000 psig ~70 kg/cm2, 66 atmospheres) while mixed in an aqueous alkaline medium having a pH greater than lO in the presence of a hydrogenation catalyst selected from the group consisting of the noble metals of Group VIII
of the Periodic Table with the proviso that, when Rl, R2, R3, R4 or R5 is chlorine, the hydrogenati~n catalyst cannot be palladium, and recovering the desired 2-aryl-2H-benzotriazole.
Taken in its broadest aspect~ one embodiment of the present invention provides a process for the production of 2-~2-hydroxy-5-methylphenyl)-2H-benzotriazole which comprises reducing and cyclizing 2-nitro-2'-hydroxy-5'-methylazobenzene with hydrogen at reducing conditions in an aqueous alkaline medium in the presence of a hydrogenation catalyst selected from the group consisting of the noble metals of group VIII of the Periodic Table, and recovering the desired 2-~2-hydroxy-5-methyl)-2H-benzotriazole.
A further embodiment of this invention is found in a process for the production of 2-~2-hydroxy-5-methyl--4a-~; `
~4~7 ~8 `phenyl)-2H-benzotriazole which comprises treating 2-nitro-2'-hydroxy-5'-methylazobenzene with hydrogen at a temperature in the range of from about 20C to about 100C and at a pressure in the range of about 1 atmosphere to about 66 atmo6pheres in an aqueous alkaline medium in the presence of a hydrogenation catalyst comprising a noble metal of Group VIl of the Periodic Table, removing the noble metal catalyst by filra-tion, lowering the pH of the aqueous system to a value less than 10 to precipitate the desired product, and recovering the desired 2-(2-hydroxy-5-methylphenyl3-2H-benzotriazole by conventional procedures.
The process of this invention can be carried out at a temperature in the range of from about 20C to about 100C, preferably from about 30C to 80C, and most preferably from about 40C to about 70C.
A specific embodiment of the invention is exemplified in a process for the production of 2-(2-hydroxy-5-methyl phenyl)-2H-benzotriazole, which comprises treating 2-nitro-
2'-hydroxy-5'-methylazobenzene with hydrogen at a temperature in the range of from about 20C to about 100C and at a pressure in the range of from about 1 to about 66 atomos-pheres in an aqueous alkaline medium in the presence of a hydrogenation catalyst comprising palladium composited on charcoal, and recovering the desired 2-(2-hydroxy-5-methyl-phenyl)-2-benzotriazole.
~5~7~
Other objects and embodimetns will be found in the following, further detailed description of this invention.
The use of organic solvents when catalytically re-ducing 2-nitroazobenzenes to form 2-aryl-2H-benzotriazoles has inherent disadvantages. One desadvantage is economic in nature involving the cost and recovery of the solvent, and the other is the well known hazard of using low boiling sol-vents when hydrogenating nitro compounds.
In order to avcid the use of organic solvents, the reduction of 2-nitro-2' hydroxy-5'-methylazobenzene was car-ried out in an aqueous alkaline solution employing sufEicient sodium hydroxide to convert the water-insoluble azobenzene intermediate into the corresponding water~soluble sodium phenolate salt. A hydrogenation catalyst comprising palladium composited on carbon was used and the reduction and cycliza-tion effected at a hydrogen pressure of from about 1 to about 5.7 atmospheres at temperatures from about 20C to about 100C, with a recovery of pure product in yields in the order of up to 77~. However, higher pressures up to about 66 atmospheres may be also used with equivalent results.
~L~5~7~1~
While many of the 2-nitro-2'-hydroxyazobenzene inter-mediates useful in this invention have such a combination of chemical and physical properties that they can be converted in strong aqueous alkaline solution into the corresponding water-soluble alkali phenolate salts, other 2-nitro-2'-hydroxyazobenzene intermediates because of their more hydro-carbon nature remaining essentially insoluble in these strong aqueous alkaline solutions. In order to facilitate required close proximity of the catalyst, hydrogen and o-nitroazo-benzene intermediate in this heterogeneous reaction, the use of a wetting or dispersing agent is required.
In the process according to the invention the 2-nitro-2'-hydroxyazobenzenes insoluble in strong aqueous alkaline solution are employed as dispersions in water. The term dis-persion is used in the present invention to describe any fine distribution of the 2-nitro-2'-hydroxyazobenzenes. Dispersions are produced by adding dispersing agents to the aqueous alkali and the appropriate 2-nitro-2'-hydroxyazobenzne compound mixtrue in a concentration between 0.1% and 5% by weight, and preferably between 0.5~ and 3% by weight, of the dispersing agent~ It is frequently necessary to stir very rapidly at the same time. This rapid stirring should be maintained after addition of the noble metal catalyst and during the hydro-genation reaction itself to maximize contact between the various components of this heterogeneous system.
~47 i~13 Examples of dispersing agents which can be used according to the invention are dispersing agents from e.g.
Ullmann, Encyklopaedie der Technischen Chemie, Third Edition, Volume 16, 1965, pages 724-741.
In the case of the anionic surface-active a~ents, the anion is shown. The cation is generally an alkali metal ion.
In the case of the cationic surface-active agents, the cation is shown. The anion is generally a chloride or methosulfate ion.
In the list below, the symbols denote the following:
R denotes a long-chain alkyl radical, R' denotes a short alkyl radical or H, and X denotes an alkylene radical, for example -(CH2)n , with n = 1-3.
7~
Anionic surface~acti~re _ ~ents _ a) Salts of carboxylic acids R-COO Soaps R-CONH-X-COO
R
~CH-S02NH-X-COO
_ Modified soaps with inter--O-X-COO
mediate members R-S-X-COO
b) Sulfuric acid Sulfated oils and fatty acids esters R-CH-X-C~ Sulfated esters I - \OR' R-CH-X-C~ Sulfated amides R-OSO3 Alkylsulfates O Sulfated fatty acid monoglyce-H rides and others -R-CONH-X-OSO3 Sulfated fatty acid alkylol-amides R-O-X-OSO Sulfated ethers 7,f~
c~ Alkylsulfonates R~H-R' Simple alkyl.sulfonates ~3 CH2--COOR \ Sulfosuccinic acid esters 03S-CH--coo~ I . , R-COI-X-So3 Alkylsulfonates with`intermediate R' members R - ~ O-X-S03 d) Alkylarylsulfonates R ~ ~lkylnaphthalenesulfona~es R--~ ~ Alkylbenæ~esulIonates e) Surface-active agents with less customary anionic groups O Alkylphosphates (variQus kinds~
Il / O ..
R ~ ~ O
Salts o~ alkylbenzenephosphonic ac.ids 7 7 1~
Cationic sur~ace~active agents a) Amine sal,s ,~
2 ¦ Primary, secondary and tertiary + ~ ~mine salts R-NH R' I
1. ./ ..
R--COO--X--NH~2 ` ~ ¦ Primary, secondary and ~ertiary ~ amine salts with intermediate members b} Quaternary ammonium salts R' ~+
R-~ -R' (Also with intermediate members, as Ri in ~he case of amine salts) c) Phosphonium salts d) Sulfonium salts ~' R' R-P~-R' and R-5 R ~
A~lphoteric surface-ac~ive agents I .
~N~X-COO- Betaines R' 7 a 8 I ~ _ R - N-X-SO Sulfobetaines R' R - N-X-O-S03 Sulfate-betaines R' Non-ionic surface-active agents a) Ethylene oxide adducts R-(O-CH -CH ) -OH Alkyl-polyethylene glycols , R ~ (O-CH2-CH2)n-OH Alkylphenyl-polyethylene glycols R CO(O CH2 C 2)n Acyl-polyethylene glycols H-(O-CH2-CH2)n-(O-~H-cH2)m ( CH2 2 n Oxethylated poly-H3 propylene glycols b) Further non-ionic surface-active agents 2 o 2 Fatty acid monoglycerides H
R-COO-c6Hll04 Anhydrous sorbitol mono-fatty acid esters R-CONH-X-OH
R-CON-X-OH ) Fatty acid alkylolamides X-OH
R-COO-cl2H210lo Sucrose mono-fatty acid esters 4771~
Effective dispersing agents are found in the cationic, anionic and non-ionic compound classes. Among the preferred dispersing agents are long chain amines, amine salts of long chain acids, alkyl polyethylene glycols, alkylphenyl poly-ethylene glycols, polyhydroxyalkyl monoesters of fatty acids and the like. The following may be m~ntioned as illustrative examples: sorbitan monooleate, sorbitol monooleate, lauryl polyethylene glycol, p-dodecylphenyl polyethylene glycol, octadecylamine salts, diethanolamine salt of myristic acid and the like. Particularly effective as wetting agents were the polyhydroxyalkyl monoesters of fatty acids such as sorbitan monooleate (Span. 80).
The catalysts which are employed in the process of this invention for effecting the reduction of o-nitroazo-benzenes to form 2-aryl-2H-benzotriazoles comprise metals selected from the noble metals of Group VIIIof the Periodic Table, the preferred metal comprising palladium although it is comtemplated within the scope of this invention that the other noble metals such as platinum, rhodium, ruthenium, osmium and iridium may also be used, although not necessarily with equivalent results. The metals may be used per se, as their oxides, or in a preferred embodiment of the invention, composited on a solid support such as carbon, silica or alumi-na. A particularly effective support comprises charcoal.
Very small quantities of catalysts are required to `7~
effect the reductive cyclization of this invention. Amounts of noble metal catalyst as low as about 0.001 to 0.0015 mol/mol of the o-nitroazobenzene to be reduced are eEfective.
~ lore catalyst can be used, but using amounts over 0.005 mol/mol of the o-nitroazobenzene is generally neither needed nor economically attractive.
me noble metal catalysts of this invention can be generally used interchangeably with one another in the instant process. However, as intimated above there are some differences between the individual metals. If the o-nitro-azobenzene starting material is substituted with a chlorine atom, the use of a palladium catalyst results in the reductive cyclization to the 2-aryl-2H-benzo-triazole, but the chlorine atom is also concomitantly cleaved off. However, sub-stitution of palladium by rhodium, the latter which appears to be a milder, more selective catalyst, results in the preparation of the 2-aryl-2H-benzotriaZOle still containing the chlorine atom. According by when the preparation of a 2-aryl-2H-benzotriazole containing chlorine on either or both aromatic rings is inv~lved, a rhodium catalyst should be used and the use of a palladium catalyst should be avoided. A preferred catalyst for the reductive cyclization of a 2-nitroazobenzene intermediate substituted with chlorine to the corresponding chlorine substituted 2-aryl-2H-benzotriazole is rhodium composited on charcoal.
As hereinbefore stated, the reduction is effected at reducing conditions including a temperature within the range of from about 20C to about 100C, a pressure ranging from about 1 to about 66 atmospheres and with sufficient aqueous alkaline solution to convert the hydroxy-substituted o-nitro-azobenzenes into their corresponding water-soluble or water-dispersed alkaline phenolate salts. The water-soluble alkaline phenolate salts are prepared by adding the appropriate hydroxy-substituted o-nitroazobenzene to an aqueous alkaline solution of sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, ammonia, barium-hydroxide, calciumhydroxide or the like. The preferred alkali-ne solution comprises from about 5 to about 15 % by weight sodium hydroxide in water. When using this aqueous alkaline solution, it is possible at the end of the reduction and cyc-lizationreaction to remove the catalyst by filtration for further recycling of desired while leaving the desired 2-aryl-2-H-benzotriazole product in aqueous solution as its alkaline salt in the case of the water-soluble salts.
In the case of the water-dispersed alkaline phenolate salts, it is necessary to have an appropriate dispersing agent also present in the system. In these cases the recovery of the catalyst requires precipitation of the curde 71!~
2-aryl-2H-benzotriazole product, separation by filtration of the curde product contaminated by the noble metal catalyst, dissolving the crude product in an organic solvent such as toluene, xylene, petroleum mineral spirits, cyclohexane, hexane, chlorobenzene, ethylene dichloride and the like, and isolation of the noble metal catalyst by filtration. The crude product now in organic solution is extracted with warm mineral acid such as 70% sulfuric acid and then recrystallized by conventional procedures.
Isolation of a product in good yield and acceptable purity is another feature of this invention. The aqueous alkali solution of the desired hydroxy-substituted 2-aryl-2H-benzo-triazole salt, preferably the sodium salt, is acidified with aqueous mineral acid, preferably sulfuric acid or hydrochloric acid, to a pH of lO or below in order to precipitate the desired hydroxy-substituted 2-aryl-2H-benzotriazole as a crude product in yields in the range of 75 to 90%. The curde product may be further purified by one of several procedures to give purified products of high purity in yields in the range of 70 to 80~. A variety of trace by-products are formed during the reduction of o-nitroazobenzens. These include the correspon-ding o-aminoazobenzenes, o-aminohydrazobenzenes,o-phenylene-diamine, anilines, aminophenols and l,2,3-benzotriazoles. Most of these by-product impurities are removed by an acid-preferably sulfuric acid, wash followed by an alcohol, prefer-ably isopropanol, wash and finally a water wash of the crude .~;
~47~
2H-benzotriazole produc~. Al-ternatively, the crude produc~ may be dissolved in an organic solvent, such as toluene, and the impurities extractd by an aqueous acid solution, and the pro-duct isolated then from organic solution by conventional pro-cedures.
The process of this invention may be effected in any suitable manner and may comprise either a batch or continuous type of operation. For example, when a batch-type operation is used, a quantity of the hydroxy-substituted o-nitroazo-benzene, water, sufficient alkali, such as sodium hydroxide, to prepare the water-soluble or water-dispersed alkaline phenolate salt along with the catalyst such as palladium composited on charcoal and dispersing agent if needed is placed in an appropriate apparatus such as a shaking or stirred autoclave. Hydrogen is pressurized in until the desired initial pressure is reached. The autoclave and the contents thereof are then heated, if needed, to the desired reaction tempera-ture and maintained thereat with agitation until slightly more than the theoretical amount of hydrogen is adsorbed and the reduction reaction is complete. At the end of this time the excess pressure is vented, the aqueous alkaline solution, usually warm, is subjected in the case of the water-soluble alkaline phenolate salts to filtration, preferably under an inerte atmosphere such as nitrogen or argon, to remove the catalyst. The solution is then brought to room temperature and acidified with mineral acid solution to precipitate the ~ `~
r~ 7~
desired hydroxy-substituted 2-aryl~2H-benzotriazole crude product, which ~ay be optionally further purified by treatment with aqueous acid and recrystallization from an organic solvent.
In the case of ~he water,dispersed alkaline phenolate salts, the mixture is just brou~ht to room temperature and acidified with mineral acid solution. The insoluble hydroxy-substituted 2-aryl-2H-benzotriazole crude product containing therein the noble metal catalyst residue is then dissolved in a solvent, such as toluene. The solution of the crude product is then filtered to remove the catalyst residue and the crude product is further purified as described above.
It is also contemplated within the scope of this invention that the preparation of the 2-aryl-2H-benzotriazoles by the reduction and cyclization o o-nitroazobenzenes may also be effected in a continuous manner, although not neces-sarily with equivalent results. For example, when a continous type operation is used, the hydroxy-substituted o-nitroazo-benzene starting material is premixed with, and dissolved or dispersed in an aqueous alkaline solution, said solution or dispersion fed continuously to a reaction zone which is main-tained at the proper operating conditions of temperature and pressure and which contains the hydrogenation catalyst.
Hydrogen is pressurized into the reaction zone by a separate means. After desired residence time, the reactor effluent is 77~3 continuously dischared and the effluent Solution is acidified to isolate the desired product. Due to the nature of the catalyst employed, a particularly effective continuous type of operation comprises a fixed bed of catalyst subjected to either an upward of downward flow of the reaction solution.
If it is desirable to carry out the reduction as a two-step process with a different operating temperature for each step, two reaction zones in series each operating at the preferred temperature range or the specific reduction step involved may be used.
The re~duction of o-nitroazobenzenes to the correspon-ding 2-aryl-2H-benzotriazoles is a two-step process as out-lined below.
C)H
R~ 0\ 1 5 _ep 1 ~_ R2 --`N2 \/\ R4 ~ , /
OH
~f ~ N~ R4 2 ~ N / ~--~
.
`. . .' Stf~p 2 R~ N~
- 20 ~
, ~ 7~
Step 1 - The reduc~ioll o the o-nitroazobenzene to the N-o~ybenzotriclzole derivative proceeds rapidly and exoth~r-mically even at low temperatuxe under the process conditions o~ this invent.ion.
Step ~ - Th~ reduction o the N oxybenæo~riazole in~.ermediate to the corresponding 2-aryl-~H-benzotriazole product goes more slowly. This reduction can be ~reatly expedited by adding more cata7yst, raising the temperature, increasing the hydrogen pressure or by combination of these fac~.ors.
Genexally, the reaction ceases when the N-oxy in termediate is completely reduced to the corresponding 2-aryl-2H-benzotriazole making for facile control of this cata1.ytic hy~rogenation process~ H~ever, with some hi~hly substituted benzotriazoles, reduction should be stopped when ~he appropri~
ate amount of hydrogen has been absorbed and reacted to prevent further reductive cleavage of the desired 2-aryl-2H-benzotria--zoles prepared. In some cases with Raney nic~el at room temperature, reduction pxoceeds beyond the desired benzotria-zol~ product to the correspondin~ 4,~,6,7~tetrailydrobenzotr.ia-zole compounds as undesired by produc's.
Specifically, the instant invention pro~rides an improved process for production of compounds having the ~ormula I
7~
O~I ~S
N ~ ~ ~R4 ~herein Rl lS hydrogen or chloriIIe~
R~ ;s hydrogen, chlorine, lower alk~yl of 1 to 4 carbon atoms, 10~7er alkoxy of 1 to ~ carbon aiams, carbo-alkoxy o~ 2 to 9 car~on atoms, carboxy or -S03H, ~ 3 ig alkyl of 1 to 12 carbon atoms, ~l};oxy of 1 to 4 carbon atoms, phenyl, phenyl subst~tuted wlth alkyl gxoups, said alkyl groups having 1 to 8 carbon atoms, cyclo-al~yl of 5 to 6 carbon atoms, carboalkoxy o~ 2 to 9 carbon atoms, chlorine, carboxyethyl or arylalkyl of 7 to 9 carbon atoms, R4 is hydrogen, lower alkyl of 1 to 4 carbon ~toms, lower alkoxy of 1 to 4 carbon atoms, chlorine or hydroxyl, and
~5~7~
Other objects and embodimetns will be found in the following, further detailed description of this invention.
The use of organic solvents when catalytically re-ducing 2-nitroazobenzenes to form 2-aryl-2H-benzotriazoles has inherent disadvantages. One desadvantage is economic in nature involving the cost and recovery of the solvent, and the other is the well known hazard of using low boiling sol-vents when hydrogenating nitro compounds.
In order to avcid the use of organic solvents, the reduction of 2-nitro-2' hydroxy-5'-methylazobenzene was car-ried out in an aqueous alkaline solution employing sufEicient sodium hydroxide to convert the water-insoluble azobenzene intermediate into the corresponding water~soluble sodium phenolate salt. A hydrogenation catalyst comprising palladium composited on carbon was used and the reduction and cycliza-tion effected at a hydrogen pressure of from about 1 to about 5.7 atmospheres at temperatures from about 20C to about 100C, with a recovery of pure product in yields in the order of up to 77~. However, higher pressures up to about 66 atmospheres may be also used with equivalent results.
~L~5~7~1~
While many of the 2-nitro-2'-hydroxyazobenzene inter-mediates useful in this invention have such a combination of chemical and physical properties that they can be converted in strong aqueous alkaline solution into the corresponding water-soluble alkali phenolate salts, other 2-nitro-2'-hydroxyazobenzene intermediates because of their more hydro-carbon nature remaining essentially insoluble in these strong aqueous alkaline solutions. In order to facilitate required close proximity of the catalyst, hydrogen and o-nitroazo-benzene intermediate in this heterogeneous reaction, the use of a wetting or dispersing agent is required.
In the process according to the invention the 2-nitro-2'-hydroxyazobenzenes insoluble in strong aqueous alkaline solution are employed as dispersions in water. The term dis-persion is used in the present invention to describe any fine distribution of the 2-nitro-2'-hydroxyazobenzenes. Dispersions are produced by adding dispersing agents to the aqueous alkali and the appropriate 2-nitro-2'-hydroxyazobenzne compound mixtrue in a concentration between 0.1% and 5% by weight, and preferably between 0.5~ and 3% by weight, of the dispersing agent~ It is frequently necessary to stir very rapidly at the same time. This rapid stirring should be maintained after addition of the noble metal catalyst and during the hydro-genation reaction itself to maximize contact between the various components of this heterogeneous system.
~47 i~13 Examples of dispersing agents which can be used according to the invention are dispersing agents from e.g.
Ullmann, Encyklopaedie der Technischen Chemie, Third Edition, Volume 16, 1965, pages 724-741.
In the case of the anionic surface-active a~ents, the anion is shown. The cation is generally an alkali metal ion.
In the case of the cationic surface-active agents, the cation is shown. The anion is generally a chloride or methosulfate ion.
In the list below, the symbols denote the following:
R denotes a long-chain alkyl radical, R' denotes a short alkyl radical or H, and X denotes an alkylene radical, for example -(CH2)n , with n = 1-3.
7~
Anionic surface~acti~re _ ~ents _ a) Salts of carboxylic acids R-COO Soaps R-CONH-X-COO
R
~CH-S02NH-X-COO
_ Modified soaps with inter--O-X-COO
mediate members R-S-X-COO
b) Sulfuric acid Sulfated oils and fatty acids esters R-CH-X-C~ Sulfated esters I - \OR' R-CH-X-C~ Sulfated amides R-OSO3 Alkylsulfates O Sulfated fatty acid monoglyce-H rides and others -R-CONH-X-OSO3 Sulfated fatty acid alkylol-amides R-O-X-OSO Sulfated ethers 7,f~
c~ Alkylsulfonates R~H-R' Simple alkyl.sulfonates ~3 CH2--COOR \ Sulfosuccinic acid esters 03S-CH--coo~ I . , R-COI-X-So3 Alkylsulfonates with`intermediate R' members R - ~ O-X-S03 d) Alkylarylsulfonates R ~ ~lkylnaphthalenesulfona~es R--~ ~ Alkylbenæ~esulIonates e) Surface-active agents with less customary anionic groups O Alkylphosphates (variQus kinds~
Il / O ..
R ~ ~ O
Salts o~ alkylbenzenephosphonic ac.ids 7 7 1~
Cationic sur~ace~active agents a) Amine sal,s ,~
2 ¦ Primary, secondary and tertiary + ~ ~mine salts R-NH R' I
1. ./ ..
R--COO--X--NH~2 ` ~ ¦ Primary, secondary and ~ertiary ~ amine salts with intermediate members b} Quaternary ammonium salts R' ~+
R-~ -R' (Also with intermediate members, as Ri in ~he case of amine salts) c) Phosphonium salts d) Sulfonium salts ~' R' R-P~-R' and R-5 R ~
A~lphoteric surface-ac~ive agents I .
~N~X-COO- Betaines R' 7 a 8 I ~ _ R - N-X-SO Sulfobetaines R' R - N-X-O-S03 Sulfate-betaines R' Non-ionic surface-active agents a) Ethylene oxide adducts R-(O-CH -CH ) -OH Alkyl-polyethylene glycols , R ~ (O-CH2-CH2)n-OH Alkylphenyl-polyethylene glycols R CO(O CH2 C 2)n Acyl-polyethylene glycols H-(O-CH2-CH2)n-(O-~H-cH2)m ( CH2 2 n Oxethylated poly-H3 propylene glycols b) Further non-ionic surface-active agents 2 o 2 Fatty acid monoglycerides H
R-COO-c6Hll04 Anhydrous sorbitol mono-fatty acid esters R-CONH-X-OH
R-CON-X-OH ) Fatty acid alkylolamides X-OH
R-COO-cl2H210lo Sucrose mono-fatty acid esters 4771~
Effective dispersing agents are found in the cationic, anionic and non-ionic compound classes. Among the preferred dispersing agents are long chain amines, amine salts of long chain acids, alkyl polyethylene glycols, alkylphenyl poly-ethylene glycols, polyhydroxyalkyl monoesters of fatty acids and the like. The following may be m~ntioned as illustrative examples: sorbitan monooleate, sorbitol monooleate, lauryl polyethylene glycol, p-dodecylphenyl polyethylene glycol, octadecylamine salts, diethanolamine salt of myristic acid and the like. Particularly effective as wetting agents were the polyhydroxyalkyl monoesters of fatty acids such as sorbitan monooleate (Span. 80).
The catalysts which are employed in the process of this invention for effecting the reduction of o-nitroazo-benzenes to form 2-aryl-2H-benzotriazoles comprise metals selected from the noble metals of Group VIIIof the Periodic Table, the preferred metal comprising palladium although it is comtemplated within the scope of this invention that the other noble metals such as platinum, rhodium, ruthenium, osmium and iridium may also be used, although not necessarily with equivalent results. The metals may be used per se, as their oxides, or in a preferred embodiment of the invention, composited on a solid support such as carbon, silica or alumi-na. A particularly effective support comprises charcoal.
Very small quantities of catalysts are required to `7~
effect the reductive cyclization of this invention. Amounts of noble metal catalyst as low as about 0.001 to 0.0015 mol/mol of the o-nitroazobenzene to be reduced are eEfective.
~ lore catalyst can be used, but using amounts over 0.005 mol/mol of the o-nitroazobenzene is generally neither needed nor economically attractive.
me noble metal catalysts of this invention can be generally used interchangeably with one another in the instant process. However, as intimated above there are some differences between the individual metals. If the o-nitro-azobenzene starting material is substituted with a chlorine atom, the use of a palladium catalyst results in the reductive cyclization to the 2-aryl-2H-benzo-triazole, but the chlorine atom is also concomitantly cleaved off. However, sub-stitution of palladium by rhodium, the latter which appears to be a milder, more selective catalyst, results in the preparation of the 2-aryl-2H-benzotriaZOle still containing the chlorine atom. According by when the preparation of a 2-aryl-2H-benzotriazole containing chlorine on either or both aromatic rings is inv~lved, a rhodium catalyst should be used and the use of a palladium catalyst should be avoided. A preferred catalyst for the reductive cyclization of a 2-nitroazobenzene intermediate substituted with chlorine to the corresponding chlorine substituted 2-aryl-2H-benzotriazole is rhodium composited on charcoal.
As hereinbefore stated, the reduction is effected at reducing conditions including a temperature within the range of from about 20C to about 100C, a pressure ranging from about 1 to about 66 atmospheres and with sufficient aqueous alkaline solution to convert the hydroxy-substituted o-nitro-azobenzenes into their corresponding water-soluble or water-dispersed alkaline phenolate salts. The water-soluble alkaline phenolate salts are prepared by adding the appropriate hydroxy-substituted o-nitroazobenzene to an aqueous alkaline solution of sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, ammonia, barium-hydroxide, calciumhydroxide or the like. The preferred alkali-ne solution comprises from about 5 to about 15 % by weight sodium hydroxide in water. When using this aqueous alkaline solution, it is possible at the end of the reduction and cyc-lizationreaction to remove the catalyst by filtration for further recycling of desired while leaving the desired 2-aryl-2-H-benzotriazole product in aqueous solution as its alkaline salt in the case of the water-soluble salts.
In the case of the water-dispersed alkaline phenolate salts, it is necessary to have an appropriate dispersing agent also present in the system. In these cases the recovery of the catalyst requires precipitation of the curde 71!~
2-aryl-2H-benzotriazole product, separation by filtration of the curde product contaminated by the noble metal catalyst, dissolving the crude product in an organic solvent such as toluene, xylene, petroleum mineral spirits, cyclohexane, hexane, chlorobenzene, ethylene dichloride and the like, and isolation of the noble metal catalyst by filtration. The crude product now in organic solution is extracted with warm mineral acid such as 70% sulfuric acid and then recrystallized by conventional procedures.
Isolation of a product in good yield and acceptable purity is another feature of this invention. The aqueous alkali solution of the desired hydroxy-substituted 2-aryl-2H-benzo-triazole salt, preferably the sodium salt, is acidified with aqueous mineral acid, preferably sulfuric acid or hydrochloric acid, to a pH of lO or below in order to precipitate the desired hydroxy-substituted 2-aryl-2H-benzotriazole as a crude product in yields in the range of 75 to 90%. The curde product may be further purified by one of several procedures to give purified products of high purity in yields in the range of 70 to 80~. A variety of trace by-products are formed during the reduction of o-nitroazobenzens. These include the correspon-ding o-aminoazobenzenes, o-aminohydrazobenzenes,o-phenylene-diamine, anilines, aminophenols and l,2,3-benzotriazoles. Most of these by-product impurities are removed by an acid-preferably sulfuric acid, wash followed by an alcohol, prefer-ably isopropanol, wash and finally a water wash of the crude .~;
~47~
2H-benzotriazole produc~. Al-ternatively, the crude produc~ may be dissolved in an organic solvent, such as toluene, and the impurities extractd by an aqueous acid solution, and the pro-duct isolated then from organic solution by conventional pro-cedures.
The process of this invention may be effected in any suitable manner and may comprise either a batch or continuous type of operation. For example, when a batch-type operation is used, a quantity of the hydroxy-substituted o-nitroazo-benzene, water, sufficient alkali, such as sodium hydroxide, to prepare the water-soluble or water-dispersed alkaline phenolate salt along with the catalyst such as palladium composited on charcoal and dispersing agent if needed is placed in an appropriate apparatus such as a shaking or stirred autoclave. Hydrogen is pressurized in until the desired initial pressure is reached. The autoclave and the contents thereof are then heated, if needed, to the desired reaction tempera-ture and maintained thereat with agitation until slightly more than the theoretical amount of hydrogen is adsorbed and the reduction reaction is complete. At the end of this time the excess pressure is vented, the aqueous alkaline solution, usually warm, is subjected in the case of the water-soluble alkaline phenolate salts to filtration, preferably under an inerte atmosphere such as nitrogen or argon, to remove the catalyst. The solution is then brought to room temperature and acidified with mineral acid solution to precipitate the ~ `~
r~ 7~
desired hydroxy-substituted 2-aryl~2H-benzotriazole crude product, which ~ay be optionally further purified by treatment with aqueous acid and recrystallization from an organic solvent.
In the case of ~he water,dispersed alkaline phenolate salts, the mixture is just brou~ht to room temperature and acidified with mineral acid solution. The insoluble hydroxy-substituted 2-aryl-2H-benzotriazole crude product containing therein the noble metal catalyst residue is then dissolved in a solvent, such as toluene. The solution of the crude product is then filtered to remove the catalyst residue and the crude product is further purified as described above.
It is also contemplated within the scope of this invention that the preparation of the 2-aryl-2H-benzotriazoles by the reduction and cyclization o o-nitroazobenzenes may also be effected in a continuous manner, although not neces-sarily with equivalent results. For example, when a continous type operation is used, the hydroxy-substituted o-nitroazo-benzene starting material is premixed with, and dissolved or dispersed in an aqueous alkaline solution, said solution or dispersion fed continuously to a reaction zone which is main-tained at the proper operating conditions of temperature and pressure and which contains the hydrogenation catalyst.
Hydrogen is pressurized into the reaction zone by a separate means. After desired residence time, the reactor effluent is 77~3 continuously dischared and the effluent Solution is acidified to isolate the desired product. Due to the nature of the catalyst employed, a particularly effective continuous type of operation comprises a fixed bed of catalyst subjected to either an upward of downward flow of the reaction solution.
If it is desirable to carry out the reduction as a two-step process with a different operating temperature for each step, two reaction zones in series each operating at the preferred temperature range or the specific reduction step involved may be used.
The re~duction of o-nitroazobenzenes to the correspon-ding 2-aryl-2H-benzotriazoles is a two-step process as out-lined below.
C)H
R~ 0\ 1 5 _ep 1 ~_ R2 --`N2 \/\ R4 ~ , /
OH
~f ~ N~ R4 2 ~ N / ~--~
.
`. . .' Stf~p 2 R~ N~
- 20 ~
, ~ 7~
Step 1 - The reduc~ioll o the o-nitroazobenzene to the N-o~ybenzotriclzole derivative proceeds rapidly and exoth~r-mically even at low temperatuxe under the process conditions o~ this invent.ion.
Step ~ - Th~ reduction o the N oxybenæo~riazole in~.ermediate to the corresponding 2-aryl-~H-benzotriazole product goes more slowly. This reduction can be ~reatly expedited by adding more cata7yst, raising the temperature, increasing the hydrogen pressure or by combination of these fac~.ors.
Genexally, the reaction ceases when the N-oxy in termediate is completely reduced to the corresponding 2-aryl-2H-benzotriazole making for facile control of this cata1.ytic hy~rogenation process~ H~ever, with some hi~hly substituted benzotriazoles, reduction should be stopped when ~he appropri~
ate amount of hydrogen has been absorbed and reacted to prevent further reductive cleavage of the desired 2-aryl-2H-benzotria--zoles prepared. In some cases with Raney nic~el at room temperature, reduction pxoceeds beyond the desired benzotria-zol~ product to the correspondin~ 4,~,6,7~tetrailydrobenzotr.ia-zole compounds as undesired by produc's.
Specifically, the instant invention pro~rides an improved process for production of compounds having the ~ormula I
7~
O~I ~S
N ~ ~ ~R4 ~herein Rl lS hydrogen or chloriIIe~
R~ ;s hydrogen, chlorine, lower alk~yl of 1 to 4 carbon atoms, 10~7er alkoxy of 1 to ~ carbon aiams, carbo-alkoxy o~ 2 to 9 car~on atoms, carboxy or -S03H, ~ 3 ig alkyl of 1 to 12 carbon atoms, ~l};oxy of 1 to 4 carbon atoms, phenyl, phenyl subst~tuted wlth alkyl gxoups, said alkyl groups having 1 to 8 carbon atoms, cyclo-al~yl of 5 to 6 carbon atoms, carboalkoxy o~ 2 to 9 carbon atoms, chlorine, carboxyethyl or arylalkyl of 7 to 9 carbon atoms, R4 is hydrogen, lower alkyl of 1 to 4 carbon ~toms, lower alkoxy of 1 to 4 carbon atoms, chlorine or hydroxyl, and
3~5 is hyclrogen, alkyl of 1 to 12 carbon atoms, chlorine, cyc loalkyl o 5 to ~ carbon atoms or arylalkyl of 7 to ~ carbon a~oms.
4~
R2 can be lower alkyl of 1 to 4 carbon atoms such as methyl, ethyl or n-butyl. R2 can also be lower alkoxy of 1 to 4 carbon atoms such as methoxy, ethoxy or n-butoxy. R2 can also be carboalkoxy or 2 to 9 carbon atoms such as carbo-methoxy, carboethoxy, or carbo-n-octoxy.
R3 can be alkyl of 1 to 12 carbon atoms such as methyl, ethyl, sec-butyl, tert-butyl, amyl, tert-octyl or n-dodecyl.
R3 can also be alkoxy of 1 to 4 carbon atoms such as methoxy, ethoxy or n-butoxy. R3 is also phenyl substituted with alkyl groups, said alkyl groups having 1 to 8 carbon atoms such as methyl, tert-butyl, tert-amyl or tert~octyl~ R3 can also be cycloalkyl of 5 to 6 carbon atoms such as cyclopentyl or cyclohexyl. R3 is also carboalkoxy or 2 to 9 carbon atoms such as carbomethoxy, carboethoxy, carbo-n-butoxy or carbo-n-octoxy. R3 is also arylalkyl or 7 to 9 carbon atoms such as benzyl, ~-methylbenzyl or ~ dimethylbenzyl.
R4 can be lower alkyl of 1 to 4 carbon atoms such as methyl, ethyl or n-butyl.
R4 can also be lower alkoxy of 1 to 4 carbon atoms such as methoxy, ethoxy or n-butyloxy.
R5 can be lower alkyl or 1 to 8 carbon atoms such as methyl, sec-butyl, tert-butyl, tert-amyl or tert-octyl.
~ 23 -~S~7~3 R5 can also be cycloalkyl of 5 to 6 carbon atoms such as cyclopentyl or cyclohexyl. R5 is also arylalkyl of 7 to 9 carbon atoms such as benzyl, a~methylbenzyl or ~,a-dimethyl-benzyl.
Preferably Rl is hydrogen.
Preferably R2 is hydrogen, chlorine, lower alkyl of 1 to 2 carbon atoms, methoxy or carboxy.
Preferably R3 is alkyl of 1 to 8 carbon atoms, cyclohexyl, phenyl, chlorine, a-methylbenzyl or carboxyethyl.
Preferably R4 is hydrogen, hydroxyl or methyl.
Preferably R5 is hydrogen, chlorine, alkyl of 1 to 8 carbon atoms, cyclohexyl, benzyl or a-methylbenzyl.
Most preferably R2 is hydrogen or chlorine.
Most preferably R3 is methyl, tert-butyl, tert-amyl, tert-octyl, sec-butyl, cyclohexyl, chlorine or carboxyethyl.
~ ost preferably R4 is hydrogen.
Most preferably R5 is hydrogen, chlorine, methyl, sec-butyl, tert-butyl, tert~amyl, tert-octyl or ~-methyl-benzyl.
- 24 ~
.
t ~ ~ i ~. :
L7~13 The process involved the reduction of an o-nitroazo-benzene intermediate of the formula II
R2 N2 ~ R~ (II) wherein Rl~ R2, R3, R4 und R5 are as described previously.
The s~arting o-nitroazobenzene intermediates are prepared by coupling the appropriate o-nitrobenzenediazonium compounds of formula III
1 ~ =N ~ ~
I O ¦ (III) R~No2 wherein Rl and R2 are as described previously and X is chlo-ride, sulfate, or other anionic species, but preferably chloride, with phenols of formula IV
~R5 (V) which couple in the ortho position tothe hydroxy group.
, ~5~7~3 The o-nitrobenzenediazonium compounds are in turn prepared by standard diazotization procedures using sodium nitrite in acid solution with the corresponding o-nitro-anilines of formula V
R~NH2 (V) For illustration purposes some specific examples of compounds of formulas IV and V are listed. These items are generally available as i~ems of commerce.
ompounds 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 71~
3/4-dichlorophen 4-phenylphenol 4-phenoxyphenol 4-o-tolylphenol 4-(3'-tert-octyl)-phenylphenol ethyl 4-hydroxybenzoate n-octyl 4-hydroxybenzoate 4-methoxyphenol 4-n-octylphenol 4-n-dodecylphenol resorcinol 4-(~-methylbenzyl)phenol 2-(~-methylbenzyl)-4-methylphenol 2-cyclohexyl-4-methylphenol 4-sec-butylphenol 2-sec~butyl-4-tert-butylphenol 2-tert-butyl-4-sec-butylphenol 4-carboxyethylphenol 2-methyl-4-carboxyethylphenol Preferably compounds of formula IV useful in this nvention are p-cresol 2,4-di-tert-butylphenol 2,4-di-tert-amylphenol 2,4-di-tert-octylphenol 7~8 2-tert-butyl-4-methylphenol 4-tert-octylphenol 4-n-octylphenol 4-n-dodecylphenol resorcinol 2-sec-butyl-4-tert-butylphenol 2-(~-methylbenzyl)-4-methylphenol Compounds of Formula V
o-nitroaniline 4-chloro-2-nitroaniline 4,5-dichloro-2-nitroaniline 4-methoxy-2-nitroaniline 4-methyl-2-nitroaniline 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 Preferably compounds of formula V useful in this invention are o-nitroaniline 4-chloro-2-nitroaniline . :
: .. .
- :
.
, 7'~
The o-nitroazobenzene intermediates of formula II
where Rl is chlorine; R2 is chlorine, lower alkyl of 1 to 4 carbon atoms, lower alkoxy of 1 to 4 carbon atoms, carboal-koxy of 2 to 9 carbon atoms; R3 is phenyl, phenyl substituted with alkyl groups said alkyl groups have 1 to 8 carbon atoms, carboalkoxy of 7 to 9 carbon atoms, aralkyl of 7 to 9 carbon atoms, alkyl of 9 to 12 carbon atoms; R4 is alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 4 carbon atoms, chlorine; and R5 is alkyl of 1 to 12 carbon atoms, chlorine, cycloalkyl of
R2 can be lower alkyl of 1 to 4 carbon atoms such as methyl, ethyl or n-butyl. R2 can also be lower alkoxy of 1 to 4 carbon atoms such as methoxy, ethoxy or n-butoxy. R2 can also be carboalkoxy or 2 to 9 carbon atoms such as carbo-methoxy, carboethoxy, or carbo-n-octoxy.
R3 can be alkyl of 1 to 12 carbon atoms such as methyl, ethyl, sec-butyl, tert-butyl, amyl, tert-octyl or n-dodecyl.
R3 can also be alkoxy of 1 to 4 carbon atoms such as methoxy, ethoxy or n-butoxy. R3 is also phenyl substituted with alkyl groups, said alkyl groups having 1 to 8 carbon atoms such as methyl, tert-butyl, tert-amyl or tert~octyl~ R3 can also be cycloalkyl of 5 to 6 carbon atoms such as cyclopentyl or cyclohexyl. R3 is also carboalkoxy or 2 to 9 carbon atoms such as carbomethoxy, carboethoxy, carbo-n-butoxy or carbo-n-octoxy. R3 is also arylalkyl or 7 to 9 carbon atoms such as benzyl, ~-methylbenzyl or ~ dimethylbenzyl.
R4 can be lower alkyl of 1 to 4 carbon atoms such as methyl, ethyl or n-butyl.
R4 can also be lower alkoxy of 1 to 4 carbon atoms such as methoxy, ethoxy or n-butyloxy.
R5 can be lower alkyl or 1 to 8 carbon atoms such as methyl, sec-butyl, tert-butyl, tert-amyl or tert-octyl.
~ 23 -~S~7~3 R5 can also be cycloalkyl of 5 to 6 carbon atoms such as cyclopentyl or cyclohexyl. R5 is also arylalkyl of 7 to 9 carbon atoms such as benzyl, a~methylbenzyl or ~,a-dimethyl-benzyl.
Preferably Rl is hydrogen.
Preferably R2 is hydrogen, chlorine, lower alkyl of 1 to 2 carbon atoms, methoxy or carboxy.
Preferably R3 is alkyl of 1 to 8 carbon atoms, cyclohexyl, phenyl, chlorine, a-methylbenzyl or carboxyethyl.
Preferably R4 is hydrogen, hydroxyl or methyl.
Preferably R5 is hydrogen, chlorine, alkyl of 1 to 8 carbon atoms, cyclohexyl, benzyl or a-methylbenzyl.
Most preferably R2 is hydrogen or chlorine.
Most preferably R3 is methyl, tert-butyl, tert-amyl, tert-octyl, sec-butyl, cyclohexyl, chlorine or carboxyethyl.
~ ost preferably R4 is hydrogen.
Most preferably R5 is hydrogen, chlorine, methyl, sec-butyl, tert-butyl, tert~amyl, tert-octyl or ~-methyl-benzyl.
- 24 ~
.
t ~ ~ i ~. :
L7~13 The process involved the reduction of an o-nitroazo-benzene intermediate of the formula II
R2 N2 ~ R~ (II) wherein Rl~ R2, R3, R4 und R5 are as described previously.
The s~arting o-nitroazobenzene intermediates are prepared by coupling the appropriate o-nitrobenzenediazonium compounds of formula III
1 ~ =N ~ ~
I O ¦ (III) R~No2 wherein Rl and R2 are as described previously and X is chlo-ride, sulfate, or other anionic species, but preferably chloride, with phenols of formula IV
~R5 (V) which couple in the ortho position tothe hydroxy group.
, ~5~7~3 The o-nitrobenzenediazonium compounds are in turn prepared by standard diazotization procedures using sodium nitrite in acid solution with the corresponding o-nitro-anilines of formula V
R~NH2 (V) For illustration purposes some specific examples of compounds of formulas IV and V are listed. These items are generally available as i~ems of commerce.
ompounds 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 71~
3/4-dichlorophen 4-phenylphenol 4-phenoxyphenol 4-o-tolylphenol 4-(3'-tert-octyl)-phenylphenol ethyl 4-hydroxybenzoate n-octyl 4-hydroxybenzoate 4-methoxyphenol 4-n-octylphenol 4-n-dodecylphenol resorcinol 4-(~-methylbenzyl)phenol 2-(~-methylbenzyl)-4-methylphenol 2-cyclohexyl-4-methylphenol 4-sec-butylphenol 2-sec~butyl-4-tert-butylphenol 2-tert-butyl-4-sec-butylphenol 4-carboxyethylphenol 2-methyl-4-carboxyethylphenol Preferably compounds of formula IV useful in this nvention are p-cresol 2,4-di-tert-butylphenol 2,4-di-tert-amylphenol 2,4-di-tert-octylphenol 7~8 2-tert-butyl-4-methylphenol 4-tert-octylphenol 4-n-octylphenol 4-n-dodecylphenol resorcinol 2-sec-butyl-4-tert-butylphenol 2-(~-methylbenzyl)-4-methylphenol Compounds of Formula V
o-nitroaniline 4-chloro-2-nitroaniline 4,5-dichloro-2-nitroaniline 4-methoxy-2-nitroaniline 4-methyl-2-nitroaniline 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 Preferably compounds of formula V useful in this invention are o-nitroaniline 4-chloro-2-nitroaniline . :
: .. .
- :
.
, 7'~
The o-nitroazobenzene intermediates of formula II
where Rl is chlorine; R2 is chlorine, lower alkyl of 1 to 4 carbon atoms, lower alkoxy of 1 to 4 carbon atoms, carboal-koxy of 2 to 9 carbon atoms; R3 is phenyl, phenyl substituted with alkyl groups said alkyl groups have 1 to 8 carbon atoms, carboalkoxy of 7 to 9 carbon atoms, aralkyl of 7 to 9 carbon atoms, alkyl of 9 to 12 carbon atoms; R4 is alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 4 carbon atoms, chlorine; and R5 is alkyl of 1 to 12 carbon atoms, chlorine, cycloalkyl of
5 to 6 carbon atoms or arylalkyl of 7 to 9 carbon atoms generally exhibit poor solubility in aqueous alkaline solu-tion. With such intermediates the use of the dispersing or wetting agents described previously is generally necessary in the process of this invention.
The 2-aryl-2H-benzotriazoles have found wide use as dyestuff intermediates, optical brightner blue fluorescent agents and selective ultraviolet light absorbing stabilizers affording valuable protection for fibers, films and a variety of polymeric structures subject to deterioration by ultra-violet radiation. These materials have become important items of commerce.
The 2-aryl-2H-benzotriazoles are complex organic molecules which require careful synthetic procedures for their production in good yield and acceptable purity.
9L~5i~7713 The present invention i5 concerned with an improved process to prepare ultraviolet stabilizers which are substi-tuted 2-aryl-2H-benzotriazoles. These are distinguished by a very slight absorption invisible light and very high fast-ness to light in various subs-trates. Particularly valuable members of these stabilizers are compounds having a free hydroxyl group in the 2-position of the aryl group linked to the 2-nitrogen of the benzotriazole and which are further substituted in the 3- and 5- or in the 4- and 5-positions by lower alkyl groups and may be substituted by a chlorine in the 5-position of the benzotrialzole nucleus.
The description, preparation and uses of these valuable substituted 2-aryl-2~-benzotriazoles are further taught in the U.S. Patent Numbers 3,004,896, 3,055,896, 3,072,585, 3,074,910, 3,189,615 and 3,230,194.
The following examples are given to illustrate the process of the present invention, but are not intended to limit the scope of the present invention in any manner what-soever.
~1S~177~
Example 1 2-(2-Hydroxy-5-methylphenyl)-2H-benzotriazole rrO a l-liter, lcw pressure, stirred hydrogenation reactor were charged under nitrogen with low speed stirring at roam temperature 85 grams of 2-nitro-2'-hydroxy-5'-methylazo~enzene (containing 45% water) dissolved in 37.2 grams of 50% sodium hydroxide solution and 200 grams of water and 1.4 grams of 5% palla-dium on charccal hydrogenation catalyst slurried in 18 grams of water. The amount of catalyst is 3% based on the azobenzene intermediate. The reactor was flushed several times with hydrogen and then pressurized to 5.7 atmospheres with hydrogen. m e reactor was then heated to 38-40 & and the contents stirred vigorously. Reaction began occurring readily in the very exothermic first reduc-tion step of the azobenzene to the N-oxybenzotriazole intermediate. me tempera-ture gradually increased to the range of 56-58&, and it was maintained at 58-60 C throughout the remainder of the reaction. The takeup of hydrogen was monitored throughout the reaction until no more hydrogen was absorbed. m e hydrogen pressure was maintained on the reactor throughout the reaction in the 5.3-4.7 atmosphere range. Slightly more than the theoretical amDunt of hydrogen was taken up, but when the reduction of the azobenzene intermediate to the de-sired 2-aryl-ZH-benzotriazole was ccmplete, further hydrogen absorption ceased.
'me time of the reduction reaction was 2.5 hours.
~-rl , ~, ~4771~3 The hydrogen remaining in the reactor was then vented, and a nitrogen atmosphere was reimposed on the reactor contents.
The reactor contents were then filtered under nitrogen to remove the palladium on charcoal catalyst dispersed there-in. The recovered catalyst was washed on the filter with a solution of 4 gra~s of 50~ sodium hydroxide solution and 16 grams of water. This catalyst was then suitable for reuse in another hydrogenation reaction after further washing.
The combined highly alkaline filtrates containing the desired product were then cooled to 50C under nitrogen and 25 grams of 70~ sulfuric acid solution was added slowly to bring the pH of the system to a value of less than 10. The slurry of a yellow precipitate which forms was held at 65-70C for 15 minutes. The yellow precipitate was then iso-lated by filtration and successively washed with water at a temperature of 65-70C, with water at room temperature, with isopropanol and finally again with water. A yellow crude product was thus isolated in a yield after drying of 34.4 grams (84% of theory).
The crude product could be further purified by washing a toluene solution of the crude product with warm sulfuric acid solution followed by recrystallization from toluene and isopropanol to give 31.5 grams (77~ theory) of pure material.
.
'78 Example 2 2-(2-Hydroxy-5-methylphenyl)-2H-benzo-triazole When the materials described in Example 1 are reacted by exactly the same procedure therein except that the reactor was pressured to 1 atmosphere of hydrogen rather than 5.7 atmospheres of hydrogen, the yield of the product, 2-(2-hydroxy-5-methyl-phenyl)-2H-benzotriazole, was comparable to that reported in Example 1, but the reduction required 5 hours rather than 2.5 hours.
Example 3 2-(2-Hydroxy-5-methylphenyl)-2H-benzotriazole When using the procedure of Example l,the 5~palladium on charcoal was replaced by an equivalent amount of 5%
platinum on charcoal, and the reactor pressurized with hydro-gen to a pressure of 3.3-2 atmospheres throughout the reaction, the yield of desired product was 40~, with a reduc-tion reaction time of 6 hours.
All of the azobenzene intermediate was consumed in this reduction, but the yield of desired product was with platinum only half of that obtained with the preferred noble metal catalyst palladium.
~4~7~3 Example 4 2-(2-H~droxy-5-methylphenyl)-2H-benzotriaæole When using the procedure of Example 1,the 5%palladium on charcoal was replaced by an equivalent amount of 5%
rhodium on charcoal, the yield of the desired product was 46% of theory with a reduction time of 5.7 hours with the reactor pressurized with hydrogen to a pressure of 3.3-2-atmospheres throughout the reaction and with a reaction tem-perature in the range of 50-80C.
All bf the azobenzene intermediate was consumed in this reduction, but the yield of the desired product was considerably less with rhodium -than with the preferred cata-lyst palladium. Rhodium appeared to fall between palladium and platinum in effecti~eness, but somewhat closer to plati-num with this specific product.
Example 5 2-(2-Hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole When using the procedure of Example 1 an e~uivalent amount of 2-nitro-2'-hydroxy-3',5'-di-tert-amylazobenzene was substituted for 2-nitro-2'-hydroxy-5'-methylazobenzene, 4 weight % of 5% palladium on charcoal catalyst based on the azobenzene intermediate was added in two portions and 0.5% by weight of the wetting agent sorbitan monooleate ISpan 80) was ~ 5~77~3 added to facilïtate dispersion and wetting of the insoluble azobenzene intermediate, the above noted product was obtained in a yield of 31.7%.
Example 6 2-(2-H~droxy~5-tert-octylphenyl)-2H-benzotriazole When using the procedure of Example 1 an equivalent amount of 2-nitro-2'-hydroxy-5'-tert-octylazobenzene is substituted for 2-nitro-2'-hydroxy-5'-methylazobenzene, the above noted product is obtained.
Example 7 5-Chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole When in Example 1, the 2-nitro-2'-hydroxy-5'-methyllazo-benzene is replaced by an equivalent amount of 2-nitro-5-chloro-2'-hydroxy-3',5'-di-tert-butylazobenzene and the 5%
palladium on.charcoal catalyst is replaced by an equivalent amount of 5% rhodium on charcoal catalyst in t:he presence of 0.5% dispersing agent sorbitan monooleate, the above noted product is obtained.
If the 5% palladium on charcoal catalyst is used, the resulting product is the deschloro compound 2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole.
~5~7~3 Example 8 5~Chloro-2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-2H-benzotriazole When in Example 1, the 2-nitro-2'-hydroxy-5'-methyl-azobenzene is replaced by an equivalent amount of 2-nltro-5-chloro-2'-hydroxy-3'-tert-butyl-5-methylazobenzene and the 5%
palladium on charcoal catalyst is replaced by a lik~ amount of 5~ rhodium on charcoal catalyst, the above noted product is obtained when the reaction is carried out in the presence of 0.5~ dispersing agent sorbitan monooleate.
The 2-aryl-2H-benzotriazoles have found wide use as dyestuff intermediates, optical brightner blue fluorescent agents and selective ultraviolet light absorbing stabilizers affording valuable protection for fibers, films and a variety of polymeric structures subject to deterioration by ultra-violet radiation. These materials have become important items of commerce.
The 2-aryl-2H-benzotriazoles are complex organic molecules which require careful synthetic procedures for their production in good yield and acceptable purity.
9L~5i~7713 The present invention i5 concerned with an improved process to prepare ultraviolet stabilizers which are substi-tuted 2-aryl-2H-benzotriazoles. These are distinguished by a very slight absorption invisible light and very high fast-ness to light in various subs-trates. Particularly valuable members of these stabilizers are compounds having a free hydroxyl group in the 2-position of the aryl group linked to the 2-nitrogen of the benzotriazole and which are further substituted in the 3- and 5- or in the 4- and 5-positions by lower alkyl groups and may be substituted by a chlorine in the 5-position of the benzotrialzole nucleus.
The description, preparation and uses of these valuable substituted 2-aryl-2~-benzotriazoles are further taught in the U.S. Patent Numbers 3,004,896, 3,055,896, 3,072,585, 3,074,910, 3,189,615 and 3,230,194.
The following examples are given to illustrate the process of the present invention, but are not intended to limit the scope of the present invention in any manner what-soever.
~1S~177~
Example 1 2-(2-Hydroxy-5-methylphenyl)-2H-benzotriazole rrO a l-liter, lcw pressure, stirred hydrogenation reactor were charged under nitrogen with low speed stirring at roam temperature 85 grams of 2-nitro-2'-hydroxy-5'-methylazo~enzene (containing 45% water) dissolved in 37.2 grams of 50% sodium hydroxide solution and 200 grams of water and 1.4 grams of 5% palla-dium on charccal hydrogenation catalyst slurried in 18 grams of water. The amount of catalyst is 3% based on the azobenzene intermediate. The reactor was flushed several times with hydrogen and then pressurized to 5.7 atmospheres with hydrogen. m e reactor was then heated to 38-40 & and the contents stirred vigorously. Reaction began occurring readily in the very exothermic first reduc-tion step of the azobenzene to the N-oxybenzotriazole intermediate. me tempera-ture gradually increased to the range of 56-58&, and it was maintained at 58-60 C throughout the remainder of the reaction. The takeup of hydrogen was monitored throughout the reaction until no more hydrogen was absorbed. m e hydrogen pressure was maintained on the reactor throughout the reaction in the 5.3-4.7 atmosphere range. Slightly more than the theoretical amDunt of hydrogen was taken up, but when the reduction of the azobenzene intermediate to the de-sired 2-aryl-ZH-benzotriazole was ccmplete, further hydrogen absorption ceased.
'me time of the reduction reaction was 2.5 hours.
~-rl , ~, ~4771~3 The hydrogen remaining in the reactor was then vented, and a nitrogen atmosphere was reimposed on the reactor contents.
The reactor contents were then filtered under nitrogen to remove the palladium on charcoal catalyst dispersed there-in. The recovered catalyst was washed on the filter with a solution of 4 gra~s of 50~ sodium hydroxide solution and 16 grams of water. This catalyst was then suitable for reuse in another hydrogenation reaction after further washing.
The combined highly alkaline filtrates containing the desired product were then cooled to 50C under nitrogen and 25 grams of 70~ sulfuric acid solution was added slowly to bring the pH of the system to a value of less than 10. The slurry of a yellow precipitate which forms was held at 65-70C for 15 minutes. The yellow precipitate was then iso-lated by filtration and successively washed with water at a temperature of 65-70C, with water at room temperature, with isopropanol and finally again with water. A yellow crude product was thus isolated in a yield after drying of 34.4 grams (84% of theory).
The crude product could be further purified by washing a toluene solution of the crude product with warm sulfuric acid solution followed by recrystallization from toluene and isopropanol to give 31.5 grams (77~ theory) of pure material.
.
'78 Example 2 2-(2-Hydroxy-5-methylphenyl)-2H-benzo-triazole When the materials described in Example 1 are reacted by exactly the same procedure therein except that the reactor was pressured to 1 atmosphere of hydrogen rather than 5.7 atmospheres of hydrogen, the yield of the product, 2-(2-hydroxy-5-methyl-phenyl)-2H-benzotriazole, was comparable to that reported in Example 1, but the reduction required 5 hours rather than 2.5 hours.
Example 3 2-(2-Hydroxy-5-methylphenyl)-2H-benzotriazole When using the procedure of Example l,the 5~palladium on charcoal was replaced by an equivalent amount of 5%
platinum on charcoal, and the reactor pressurized with hydro-gen to a pressure of 3.3-2 atmospheres throughout the reaction, the yield of desired product was 40~, with a reduc-tion reaction time of 6 hours.
All of the azobenzene intermediate was consumed in this reduction, but the yield of desired product was with platinum only half of that obtained with the preferred noble metal catalyst palladium.
~4~7~3 Example 4 2-(2-H~droxy-5-methylphenyl)-2H-benzotriaæole When using the procedure of Example 1,the 5%palladium on charcoal was replaced by an equivalent amount of 5%
rhodium on charcoal, the yield of the desired product was 46% of theory with a reduction time of 5.7 hours with the reactor pressurized with hydrogen to a pressure of 3.3-2-atmospheres throughout the reaction and with a reaction tem-perature in the range of 50-80C.
All bf the azobenzene intermediate was consumed in this reduction, but the yield of the desired product was considerably less with rhodium -than with the preferred cata-lyst palladium. Rhodium appeared to fall between palladium and platinum in effecti~eness, but somewhat closer to plati-num with this specific product.
Example 5 2-(2-Hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole When using the procedure of Example 1 an e~uivalent amount of 2-nitro-2'-hydroxy-3',5'-di-tert-amylazobenzene was substituted for 2-nitro-2'-hydroxy-5'-methylazobenzene, 4 weight % of 5% palladium on charcoal catalyst based on the azobenzene intermediate was added in two portions and 0.5% by weight of the wetting agent sorbitan monooleate ISpan 80) was ~ 5~77~3 added to facilïtate dispersion and wetting of the insoluble azobenzene intermediate, the above noted product was obtained in a yield of 31.7%.
Example 6 2-(2-H~droxy~5-tert-octylphenyl)-2H-benzotriazole When using the procedure of Example 1 an equivalent amount of 2-nitro-2'-hydroxy-5'-tert-octylazobenzene is substituted for 2-nitro-2'-hydroxy-5'-methylazobenzene, the above noted product is obtained.
Example 7 5-Chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole When in Example 1, the 2-nitro-2'-hydroxy-5'-methyllazo-benzene is replaced by an equivalent amount of 2-nitro-5-chloro-2'-hydroxy-3',5'-di-tert-butylazobenzene and the 5%
palladium on.charcoal catalyst is replaced by an equivalent amount of 5% rhodium on charcoal catalyst in t:he presence of 0.5% dispersing agent sorbitan monooleate, the above noted product is obtained.
If the 5% palladium on charcoal catalyst is used, the resulting product is the deschloro compound 2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole.
~5~7~3 Example 8 5~Chloro-2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-2H-benzotriazole When in Example 1, the 2-nitro-2'-hydroxy-5'-methyl-azobenzene is replaced by an equivalent amount of 2-nltro-5-chloro-2'-hydroxy-3'-tert-butyl-5-methylazobenzene and the 5%
palladium on charcoal catalyst is replaced by a lik~ amount of 5~ rhodium on charcoal catalyst, the above noted product is obtained when the reaction is carried out in the presence of 0.5~ dispersing agent sorbitan monooleate.
Claims (24)
1. A process for the production of 2-aryl--2H-benzo-triazoles of the formula I
(I) wherein Rl is hydrogen or chlorine, R2 is hydrogen, chlorine, lower alkyl of 1 to 4 carbon atoms, lower alkoxy of 1 to 4 carbon atoms, carboalkoxy of 2 to 9 carbon atoms, carboxy or -S03H, R3 is alkyl of 1 to 12 carbon atoms, alkoxy of 1 to 4 carbon atoms, phenyl, phenyl substituted with alkyl groups, said alkyl groups having 1 to 8 carbon atoms, cycloalkyl of 5 to 6 carbon atoms, carboalkoxy of 2 to 9 carbon atoms, chlorine, carboxyethyl or arylalkyl of 7 to 9 carbon atoms, R4 is hydrogen, lower alkyl of 1 to 4 carbon atoms, lower alkoxy of 1 to 4 carbon atoms, chlorine or hydroxyl, and R5 is hydrogen, alkyl of 1 to 12 carbon atoms, chlori-ne, cycloalkyl of 5 to 6 carbon atoms or arylalkyl of 7 to 9 carbon atoms, which comprises reducing and cyclizing the corresponding o-nitro-azobenzene with hydrogen at a temperature in the range of from about 20°C to about 100°C and at a pressure in the range of from about 15 psig (1.05 kg/cm , l atmosphere) to about 1000 psig (70 kg/cm2, 66 atmospheres) while mixed in an aqueous alkaline medium having a pH greater than 10 in the presence of a hydrogenation catalyst selected from the groups consisting of the noble metals of Group VIII of the Periodic Table with the proviso that, when Rl, R2, R3, R4 or R5 is chlorine, the hydrogenation catalyst cannot be palla-dium, and recovering the desired 2-aryl-2H-benzotriazole.
(I) wherein Rl is hydrogen or chlorine, R2 is hydrogen, chlorine, lower alkyl of 1 to 4 carbon atoms, lower alkoxy of 1 to 4 carbon atoms, carboalkoxy of 2 to 9 carbon atoms, carboxy or -S03H, R3 is alkyl of 1 to 12 carbon atoms, alkoxy of 1 to 4 carbon atoms, phenyl, phenyl substituted with alkyl groups, said alkyl groups having 1 to 8 carbon atoms, cycloalkyl of 5 to 6 carbon atoms, carboalkoxy of 2 to 9 carbon atoms, chlorine, carboxyethyl or arylalkyl of 7 to 9 carbon atoms, R4 is hydrogen, lower alkyl of 1 to 4 carbon atoms, lower alkoxy of 1 to 4 carbon atoms, chlorine or hydroxyl, and R5 is hydrogen, alkyl of 1 to 12 carbon atoms, chlori-ne, cycloalkyl of 5 to 6 carbon atoms or arylalkyl of 7 to 9 carbon atoms, which comprises reducing and cyclizing the corresponding o-nitro-azobenzene with hydrogen at a temperature in the range of from about 20°C to about 100°C and at a pressure in the range of from about 15 psig (1.05 kg/cm , l atmosphere) to about 1000 psig (70 kg/cm2, 66 atmospheres) while mixed in an aqueous alkaline medium having a pH greater than 10 in the presence of a hydrogenation catalyst selected from the groups consisting of the noble metals of Group VIII of the Periodic Table with the proviso that, when Rl, R2, R3, R4 or R5 is chlorine, the hydrogenation catalyst cannot be palla-dium, and recovering the desired 2-aryl-2H-benzotriazole.
2. A process according to Claim l, wherein said o-nitroazobenzene forms a water-soluble alkaline phenolate salt in said aqueous alkaline medium, which further comprises isolating said noble metal catalyst by filtration at the completion of the reaction, lowering the pH of the aqueous alkaline medium to a value of less than 10 to precipitate the desired product, and recovering the desired 2-aryl-2H-benzotriazole by conventional procedures.
3. A process according to Claim 1, wherein said o-nitroazobenzene forms a water-dispersed alkaline phenolate salt in the said aqueous alkaline medium containing addition-ally a dispersing agent or mixture of dispersing agents, which further-comprises lowering the pH of the aqueous alkaline medium to a value less than 10 at the completion of the reaction, isolating the crude desired product admixed with said noble metal catalyst by filtration, dissolving said crude desired product in an organic solvent, removing the noble metal catalyst by filtration, and recovering the desired 2-aryl-2H-benzotriazole by conventional procedures.
4. A process according to Claim 1 wherein the hydrogenation catalyst is selected from the group consisting of palladium, platinum and rhodium.
5. A process according to Claim 1 wherein the hydrogention catalyst is palladium.
6. A process according to Claim 5 characterized in that said palladium is composited on charcoal.
7. A process according to Claim 5 for the production of a compound of formula I wherein Rl is hydrogen, R2 is hydrogen, lower alkyl of 1 to 2 carbon atoms, methoxy or carboxy, R3 is alkyl of 1 to 8 carbon atoms, cyclohexyl, phenyl .alpha.-methylbenzyl or carboxyethyl, R4 is hydrogen, hydroxyl or methyl, and R5 is hydrogen, alkyl of 1 to 8 carbon atoms, cyclo-hexyl, benzyl or .alpha.-methylbenzyl.
8. A process according to Claim 5 for production of a compound of formula I wherein Rl is hydrogen, R2 is hydrogen or 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 .alpha.-methylbenzyl.
9. A process for the production of 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole which comprises reducing and cyclizing 2-nitro-2'-hydroxy-S'-methylazobenzene with hydrogen at a temperature in the range of 38-60°C
and at a pressure in the range of from about 1.0-5.7 atmospheres while mixed in an aqueous alkaline medium having a pH greater than 10 in the presence of palladium, rhodium, or platinum, and recovering the product.
and at a pressure in the range of from about 1.0-5.7 atmospheres while mixed in an aqueous alkaline medium having a pH greater than 10 in the presence of palladium, rhodium, or platinum, and recovering the product.
10. A process for the production of 2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole which comprises reducing and cyclizing 2-nitro-2'-hydroxy-5'-tert-octylazobenzene with hydrogen at a temperature in the range of 38-60°C
and at a pressure in the range of from about 4.7-5.7 atmospheres while mixed in an aqueous alkaline medium having a pH greater than 10 in the presence of palladium, and recovering the product.
and at a pressure in the range of from about 4.7-5.7 atmospheres while mixed in an aqueous alkaline medium having a pH greater than 10 in the presence of palladium, and recovering the product.
11. A process for the production of 2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole which comprises reducing and cyclizing 2-nitro-2'-hydroxy-3',5',di-tert-amylazobenzene with hydrogen at a temperature in the range of 38-60°C and at a pressure in the range of from about 4.7-5.7 atmos-pheres while mixed in an aqueous alkaline medium having a pH greater than 10 in the presence of palladium, and recovering the product.
12. A process according to claim 1 wherein the hydrogenation catalyst is rhodium.
13. A process according to claim 12 characterized in that the said rhodium is composited on charcoal.
14. A process according to claim 12 for a production of a compound of formula I, wherein Rl is hydrogen R2 is hydrogen, chlorine, lower alkyl of 1 to 2 carbon atoms, methoxy or carboxy, R3 is alkyl of 1 to 8 carbon atoms, cyclohexyl, phenyl, chlorine, .alpha.-methylbenzyl or carboxyethyl, R4 is hydrogen, hydroxyl or methyl, and R5 is hydrogen, alkyl of 1 to 8 carbon atoms, chlorine, cyclohexyl, benzyl or .alpha.-methylbenzyl.
15. A process according to claim 12 for production of a compound of formula I wherein Rl is hydrogen, R2 is hydrogen or chlorine, R3 is methyl, sec-butyl, tert-butyl, tert-amy , tert-octyl, cyclohexyl, chlorine or carboxyethyl, R4 is hydrogen, and R5 is hydrogen, chlorine> methyl, tert-butyl, sec-butyl, tert-amyl, tert-octyl or .alpha.-methylbenzyl.
16. The process for the production of 5-chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole which comprises reducing the cyclizing 2-nitro-5-chloro-2'-hydroxy-3',5'-di-tert-butylazoobenzene with hydrogen at a temperature range of 38-60°C and at a pressure in the range of from about 4,7-5.7 atmospheres while mixed in an aqueous alkaline medium having a pH
greater than 10 in the presence of rhodium and recovering the product
greater than 10 in the presence of rhodium and recovering the product
17. The process for the production of 5-chloro-2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-2H-benzotriazole which comprises reducing and cyclizing 2-nitro-5-chloro-2'hydroxy-3'-tert-butyl-5-methylazobenzene with hydrogen at a temperature range of 38-60°C and at a pressure in the range of from about 4.7-5.7 atmospheres while mixed in an aqueous alkaline medium having a pH greater than 10 in the presence of rhodium and recovering the product.
18. A process for the production of 2-aryl-2H-benzotriazole of Formula I
wherein:
Rl is hydrogen or chlorine; R2 is hydrogen, chlorine and lower alkyl of 1 to 4 carbon atoms; R3 is alkyl of 1 to 8 carbon atoms and chlorine; R4 is hydrogen, lower alkyl of 1 to 4 carbon atoms and chlorine; R5 is hydrogen, alkyl of 1 to 8 carbon atoms and chlorine; comprising reducing and cyclizing the corresponding o-nitroazobenzene of the Formula II
with hydrogen at a temperature in the range of 20°C to about 100°C and at a pres-sure of 1 to 66 atmospheres while dissolved in an aqueous alkaline medium con-taining an alkali metal hydroxide as base and having a pH greater than 10 in the presence of a hydrogenation catalyst selected from platinum, palladium, nickel, cobalt, rhodium or molybdenum with the proviso that when Rl, R2, R3, R4 and R5 is chlorine, the hydrogenation catalyst cannot be palladium and recovering the desired 2-ary1-2H-benzotriazole.
wherein:
Rl is hydrogen or chlorine; R2 is hydrogen, chlorine and lower alkyl of 1 to 4 carbon atoms; R3 is alkyl of 1 to 8 carbon atoms and chlorine; R4 is hydrogen, lower alkyl of 1 to 4 carbon atoms and chlorine; R5 is hydrogen, alkyl of 1 to 8 carbon atoms and chlorine; comprising reducing and cyclizing the corresponding o-nitroazobenzene of the Formula II
with hydrogen at a temperature in the range of 20°C to about 100°C and at a pres-sure of 1 to 66 atmospheres while dissolved in an aqueous alkaline medium con-taining an alkali metal hydroxide as base and having a pH greater than 10 in the presence of a hydrogenation catalyst selected from platinum, palladium, nickel, cobalt, rhodium or molybdenum with the proviso that when Rl, R2, R3, R4 and R5 is chlorine, the hydrogenation catalyst cannot be palladium and recovering the desired 2-ary1-2H-benzotriazole.
19. A process as in claim 18 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-(2'-nitrophenylazo)p-cresol and the result-ing benzotriazole compound of Formula I is 2-(2'-benzotriazolyl)p-cresol.
20. A process as in claim 18 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-nitro-2'-hydroxy-5'-tert.octylazohenzene and the resulting benzotriazole compound of Formula I is 2-(2-hydroxy-5-tert.-octylphenyl)-2H-benzotriazole.
21. A process as in claim 18 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-nitro-2'-hydroxy-3',5',di-ter amylazo-benzene and the resulting benzotriazole compound of Formula I is 2-(2-hydroxy 3',5',di-tert.amylphenyl)-2H-benzotriazole.
22. A process as in claim 18 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-nitro-5-chloro-2'-hydroxy-3'-tert.-butyl-5'-methylazobenzene and the resulting benzotriazole compound of Formula I is 5-chloro-2-(2-hydroxy-3-tert.butyl-5-methylphenyl)-2H-benzotriazole.
23. A process as in claim 18 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-nitro-5-chlor-2'-hydroxy-3',5',di-tert.-butylazobenzene and the resulting benzotriazole compound of Formula I is 5-chloro-2-(2-hydroxy-3',5',di-tert.butylphenyl)-2H-benzotriazole.
24. A process for the production of 2-aryl-2H-benzotriazole of Formula I
wherein:
R1 is hydrogen or chlorine; R2 is hydrogen, chlorine and lower alkyl of 1 to 4 carbon atoms; R3 is alkyl of 1 to 8 carbon atoms and chlorine; R4 is hydrogen, lower alkyl of 1 to 4 carbon atoms and chlorine; R5 is hydrogen, alkyl of l to 8 carbon atoms and chlorine;
comprising reducing and cyclizing the corresponding o-nitroazobenzene of the Formula II
with hydrogen at a temperature in the range of 20°C to about 100°C and at a pressure of 1 to 66 atmospheres while dissolved in an aqueous alkaline medium having a pH greater than 10 in the presence of a hydrogenation catalyst selected from platinum, palladium, nickel, cobalt, rhodium or molybdenum with the proviso that when Rl, R2, R3, R4 and R5 is chlorine, the hydrogenation catalyst cannot be palladium and recovering the desired 2-aryl-2H-benzotriazole.
(25) A process as in claim 24 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-(2'-nitrophenylazo)p-cresol and the result-ing benzotriazole compound of Formula I is 2-(2'-benzotriazolyl)p-cresol.
(26) A process as in claim 24 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-nitro2'-hydroxy-5'-tert.octylazobenzene andthe resulting benzotriazole compound of Formula I is 2-(2-hydroxy-5-tert.-octylphenyl)-2H-benzotriazole.
(27) A process as in claim 24 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-nitro-2'-hydroxy-3',5',di-tert.amylazo-benzene and the resulting benzotriazole compound of Formula I is 2-(2-hydroxy-3',5',di-tert.amylphenyl)-2H-benzotriazole.
(28) A process as in claim 24 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-nitro-5-chloro-2'-hydroxy-3'-tert.-butyl-5'-methylazobenzene and the resulting benzotriazole compound of Formula I
is 5-chloro-2-(2-hydroxy-3-tert.butyl-5-methylphenyl)-2H-benzotriazole.
(29) A process as in claim C24 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-nitro-5-chloro-2'-hydroxy-3',5',di-tert.-butylazobenzene and the resulting benzotriazole compound of Formula I is 5-chloro-2-(2-hydroxy-3',5'-di-tert.butylphenyl)-2H-benzotriazole.
wherein:
R1 is hydrogen or chlorine; R2 is hydrogen, chlorine and lower alkyl of 1 to 4 carbon atoms; R3 is alkyl of 1 to 8 carbon atoms and chlorine; R4 is hydrogen, lower alkyl of 1 to 4 carbon atoms and chlorine; R5 is hydrogen, alkyl of l to 8 carbon atoms and chlorine;
comprising reducing and cyclizing the corresponding o-nitroazobenzene of the Formula II
with hydrogen at a temperature in the range of 20°C to about 100°C and at a pressure of 1 to 66 atmospheres while dissolved in an aqueous alkaline medium having a pH greater than 10 in the presence of a hydrogenation catalyst selected from platinum, palladium, nickel, cobalt, rhodium or molybdenum with the proviso that when Rl, R2, R3, R4 and R5 is chlorine, the hydrogenation catalyst cannot be palladium and recovering the desired 2-aryl-2H-benzotriazole.
(25) A process as in claim 24 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-(2'-nitrophenylazo)p-cresol and the result-ing benzotriazole compound of Formula I is 2-(2'-benzotriazolyl)p-cresol.
(26) A process as in claim 24 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-nitro2'-hydroxy-5'-tert.octylazobenzene andthe resulting benzotriazole compound of Formula I is 2-(2-hydroxy-5-tert.-octylphenyl)-2H-benzotriazole.
(27) A process as in claim 24 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-nitro-2'-hydroxy-3',5',di-tert.amylazo-benzene and the resulting benzotriazole compound of Formula I is 2-(2-hydroxy-3',5',di-tert.amylphenyl)-2H-benzotriazole.
(28) A process as in claim 24 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-nitro-5-chloro-2'-hydroxy-3'-tert.-butyl-5'-methylazobenzene and the resulting benzotriazole compound of Formula I
is 5-chloro-2-(2-hydroxy-3-tert.butyl-5-methylphenyl)-2H-benzotriazole.
(29) A process as in claim C24 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-nitro-5-chloro-2'-hydroxy-3',5',di-tert.-butylazobenzene and the resulting benzotriazole compound of Formula I is 5-chloro-2-(2-hydroxy-3',5'-di-tert.butylphenyl)-2H-benzotriazole.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US57738375A | 1975-05-14 | 1975-05-14 | |
| US577,383 | 1975-05-14 | ||
| US66979276A | 1976-03-23 | 1976-03-23 | |
| US669,792 | 1991-03-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1154778A true CA1154778A (en) | 1983-10-04 |
Family
ID=27077225
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000250324A Expired CA1154778A (en) | 1975-05-14 | 1976-04-15 | Process for the production of 2-aryl-2h- benzotriazoles |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1154778A (en) |
| IT (1) | IT1071651B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4990623A (en) * | 1986-07-28 | 1991-02-05 | Berenbaum Morris B | Sulfonated 2-(2'-hydroxyaryl)-2H-benzotriazoles and/or sulfonated aromatic formaldehyde condensates |
-
1976
- 1976-04-15 CA CA000250324A patent/CA1154778A/en not_active Expired
- 1976-05-13 IT IT2324076A patent/IT1071651B/en active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4990623A (en) * | 1986-07-28 | 1991-02-05 | Berenbaum Morris B | Sulfonated 2-(2'-hydroxyaryl)-2H-benzotriazoles and/or sulfonated aromatic formaldehyde condensates |
Also Published As
| Publication number | Publication date |
|---|---|
| IT1071651B (en) | 1985-04-10 |
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