CA1154779A - Process for the production of 2-aryl-2h- benzotriazoles - Google Patents

Abstract

Abstract of the Disclosure A process for the production of 2-aryl-2H-benzotriazoles having the formula I

(I) comprises reducing and cyclizing the corresponding o-nitro-azobenzenes having the formula II

(II) 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 alkaline medium at a pH over 10 in the presence of a nickel catalyst, preferably molybdenum-promoted Raney nickel. High yields of pure product are obtained directly with a concomitant reduction of undesired by-product and a reduction in effluent pollution problems.

Description

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This invention pertains to a process for the preparation of 2-aryl-2H-benzotriazoles and derivatives thereof. More particularly, the invention relates to a novel process for preparing 2-aryl-2H-benzotriazoles where-by high yields of the desired products are obtained and ef-fluent pollution problems occurring with present processes for making such products are essentially eliminated.

Heretofore, the conversion of an ortho-nitroazo-benzene to the corresponding 2-aryl-2H-benzotriazole has been accomplished by chemical and electrolytic reduction pro-cesses. 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 hy-droxide solutions to give good yields of the corresponding

2-aryl-2H-benzotriazoles. Ammonium sulfide, alkali sulfides, zinc with ammonia at 80-100C, sodium hydrosulfide and zinc with hydrochloric acid have also been used as the chemical reducing agents for this transformation as disclosed in U.S. Patent 2,362,988. The use of ammonium sulfide was also reported by S.N. Chakrabarty et al, J. Indian Chem. Soc., 5, 555 tl928); 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.

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~ Electrolytic reduction of o-n:Ltroazobenzenes was reported by H. Itomi, Mem. Coll. Sci. Kyol:o 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 embodi-ments 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-benzotriazoles varied from 30 to 85% depending on the specific o-nitroazobenzene intermediate reduced.

The known chemical and electrolytic reduction processes for preparing 2-aryl-2H-benzotriazoles are not practical 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 reduction in alkaline medium o o-nitrophenylhydrazine and selected phenyl ring substituted alkyl and perfluoroalkyl derivatives .

thereof was repoTted in Japancse patent publication, Sho 48-26012, August 3, 1973. The isomeric 2~1-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 avoiding severe pollution and environmental problems.
A further object of this invention is to prepare 2-aryl-2H-ben70triazoles by reducing and cyclizing the corresponding o-nitroazobenzene under certain conditions hereinafter set ~orth in grea~er detail wher~by 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 OH R5 N~ ~ (I) ~ R3 wheTein 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 atoms9 phenylJ phenyl substituted with alkyl groups, said alkyl groups ha~ing 1 to 8 carbon atomsJ cycloalkyl of 5 to 6 carbon atomsJ 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 atomsJ chlorine or hydroxyl, and R5 is hydrogen, alkyl of 1 to 12 carbon atoms, chlorine, cycloalkyl of 5 to 6 carbon atoms or arylalkyl of 7 to 9 atoms, which comprises 7 i ~

reducing and cyclizing ~he corresponding o-nitroazobenzene with hydrogen at a temperature in the range of from about 20C to about 100C and at a pressure in the range from about 1 atomsphere to abou~ 66 atmospheres while mixed in an alkaline medium having a pH greater than 10 in the presence of a nickel hydrogenation catalyst, and recovering the desired 2-aryl-2H-benzotriazole.
Preferably the catalyst is a promoted nickel hydrogenation catalyst.
Taken in its broadest aspect, one embodiment of this invention is found in 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 alkalinemedium in the presence of a nickel hydrogenation catalyst, and recovering the desired 2-(2-hydroxy-S-methyl)-2H-benzotriazole.

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Taken in its broadest aspect, another embodiment of this invention is found in a process for the production of 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole which com-prises reducing and cyclizing 2-nitro-2'-hydroxy-5'-methyl-azobenzene with hydrogen at reducing conditions in an alkaline aqueous organic medium in the presence of a nickel hydrogena-tion catalyst, and recovering the desired 2-(2-hydroxy-5-methyl)-2H-benzotriazole.

Taken in its broadest aspect, still another em-bodiment of this invention is found in 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 reducing conditions in an organic solvent system con-taining a water-soluble amine in the presence of a promoted nickel hydrogenation catalyst and recovering the desired 2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole.

The process of this invention can be carried out at a tempe.rature in the range of from about 20C to about 100C, preferably from about 30C to about 80C, and most preferably from about 40C to about 70C.

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~ further embodiment o~ this invention is found in a process for the production ox 2-(2-hydroxy-5-methyl-phenyl)-2H benzotriazole which comprises~trea~ing 2-nitro-2'-hydroxy-5'-methylazobenzene with hydrogen at a tempera-ture in the range of from about 20C to about 100C and at a pressure in the range of about 1 atmosphere to about 66 atmospheres in an aqweous alkaline medium in the presence of promoted or unpromoted nickel hydrogenation catalyst, removing the nickel catalyst by filtration, lowering the pH
of the aqueous system to a value less than lO to precipitate the desired product, and recovering the desired ~_(2-hydroxy-5-methylphenyl)_2H~benzo-triazole by conventional procedures. One preferred alkaline medium is an aqueous alkali metal hydroxide solution.

A f.urther embodiment of this invention is found in a process for the production of 2_(2-hydroxy-5-methylphenyl)-2H-benzotriazole which comprises treating 2-nitro-2' hydroxy-5'_methylazobenzene with hydrogen at a temperature in the range o~ from about ~0C to about lOO''C and at a pressure in the range of about 1 atmosphere to about, 66 atmospheres in an alkaline aqueous organic (preferably isopropanol) medium in the presence of a promoted or unpromoted nickel hydrogenation catalyst, removing the catalyst by filtration, lowering the pH of the aqueous system to a value less ~han 4 to precipitate the desired product, and recovering the dPsired 2- (2-hydroxy-S_methylphenyl)_2H_benzotriazole by conventional procedures.One preferred alkaline medium is an aqueous alkali metal hydroxide/alkanol solution.

A further embodiment of this invention is found in a process for the production of 2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole which comprises treating 2-nitro-2'-hydroxy-3',5'-di-tert-amylazobenzene with hydro-gen at a temperature in the range of fro~ about 20 ~C to about 100~C and at a pressure in the ran~e of about 1 atmosphere to about 66 atmospheres in an organic solvent system containing a water-soluble amine, preferably isopro-panol/diethylamine, in the presence of a pr~moted or unprQ-moted nickel hydrogenation catalyst, removing the metal catalyst by filtration, and recovering the desired 2-(2-hydroxy~3,5-di-tert-amylphenyl)-2H_benzotriazole by conven-tional procedures.

. A further embodiment of this invention is found 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 tempera-ture in the range of from about 20C to about 100C and - at a pressure in the range of about 1 atmosphere to about 547-~

66 atmospheres in an organic solvent system containing a water_soluble amine (preferably toluene/methanol/diethylami.ne) in the presence of a promoted or unpr~noted nickel hydrogena~
tion catalyst, removing the metal catalyst by filtration~ and recovering the desired 2-(2-hydroxy~5 methylphenyl)_2H_benzo-triazole by con~entional procedures .~
A spe~ific embodiment of the invention is exempli--fied in a process for the produc~ion of 2-~2-hydroxy-5--methylphenyl)-2H-benzotriazole, which comprises treating 2 nitro-2'-hydroxy-5'-methylazobenzene with hydrogen at a temperature in the range of from about 20C to ahout 100C
and at a pressure in the range of ~rom ahout 1 atmosphere to about 66 atmospheres in an aqueous alkaline medium in the presence of a hydrogenation catalyst comprising molybdenum-promoted Raney nickel, and recovering the desired 2_(2-hydroxy_5_methylphenyl)_2H_benzotriazole.

A specific embodiment of the invent.ion is exem-plified in a process for the production of 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole, which comprises treating ~-nitro-2'-hydroxy-S'-methylazobenzene with hydrogen at a temperature in the rarge of from about 20C to about 100C
and at a pressure in the range of from about 1 atmosphere to about 66 atmospheres in an alkaline aqueous organic medium, preferably aqueous sodiurn hydroxide/i.sopropanol, in the pre~
sence of a hydrogenation catalyst c~nprisirlg molybdenum_ ~ 8 ~

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promoted Raney nickel, and recovering the desired 2-(2-hydroxy-5-methyl-phenyl)-2H-benzotriazole.
Another specific embodiment of the invention is exemplified in a process for the production of 2-~2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole, which comprises treating 2-nitro-2'-hydroxy-3',5'-di-tert-amylazobenzene 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 15 psia to about 1000 po~nds per square inch (about 1.05 to about 70 kg/cm ) in an organic solvent system containing a water-soluble amine, such as isopropanol/diethylamine or toluene/methanol/diethylamine solution, in the presence of a hydrogenation catalyst comprising molybdenum-promoted Raney nickel, and recovering the desired 2-(2-hydroxy-3,5-di-tert-amyl-phenyl)-2H-benzotriazole.
Still another embodiment is exemplified where this process is carried out in an organic solvent system consisting essentially entirely of an organic aliphatic or alicyclic amine, such as n-propylamine, or morpholine.
A further specific embodiment of this exemplified in the process for the production of 2-~2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole which comprises treating 2-nitro-2'-hydroxy-3',5'-di-tert-amylazobenzene with hydrogen at a temperature in the range of from about 20 C to about 100C and at a pressure in the range of from about 1 atmosphere to ~l - 9 _ .

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about 66 atmospheres in an alkaline aqueous organic solvent system containing a water immiscible organic hydrocarbon material such as Amsco mineral spirits and an alkali metal hydroxide, preferably potassium hydroxide, in the presence of a wetting agent to facilitate intimate contact of the various ingredients in the heterogeneous system one a hydrogenation catalyst comprising molybdenum-promoted Raney nickel, and recovering the desired 2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole.

Other objects and embodiments will be found in the following, further detailed description of this invention.

The reduction of 2-nitro-2'-hydroxy-5'-methylazo-benzene was carried out in an aqueous alkaline solution employing sufficient sodium hydroxide to convert the water-insoluble azobenzene intermediate into the corresponding water-soluble sodium phenolate salt. A hydrogenation catalyst comprising molbdenum-promoted Raney nickel was used and the reduction and cyclization effected a a hydrogen pressure of from about 1 to abou~ 5.7 atmospheres at temperatures from about 20C to about 100C, with a recovery of pure product in yields on the order of up to 77%. However, higher pressures up to about 66 atmospheres may also be used with equivalent results.

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While many of the 2-nitro-2'-hydroxyazobenzene intermediates useful in this invention have such a combination of chemical and physical properties that they can be con-verted in strong aqueous alkaline solution into the corres-ponding water-soluble alkali phenolate salts, other 2 nitro-2'-hydroxyazobenzene intermediates because of their more hydrocarbon nature remain essentially insoluble in these strong aqueous alkaline solutions. In order to facilitate the required close proximity of the catalyst, hydrogen and o-nitroazobenzene intermediate in this heteroo~eneous 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 dispersion is used in the present invention to des-cribe any fine distribution of the 2-nitro-2'-hydroxyazo-benzenes. Dispersions are produced by adding dispersing agents to the aqueous alkali and the appropriate 2-nitro-2'-hydroxyoxyazobenzene compound mixture 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 nickel catalyst and during the hydrogenation reaction itself to maximize contact between the various components of this heterogeneous system.

~ 5~ g Examples of dispersing agents which can be used according to the inventions are dispersing agents from the following list [Ullmann, Encyklopaedie der Technischen Chemie (Encyclopedia of Industrial Chemistry), Third Edition, Volume 16, 1965, pages 724-741] which is incorporated by reference.

In the case of the anionic surface-active agents, 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 this list below, the symbols denote the following:

R denotes a long-chain aIkyl radicall R' denotes a short alkyl radical or H, and X denotes an alkylene radical, for example -(CH2) -, with n = 1-3.

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Anionic surface-active agènts .

a) Salts o~ carboxylic acids R-COO . Soaps R-CONH-X-C~O
R

R Modified soaps with intermediate members R-O-S-COO
R-S-X-COO
R-SO -X--COO
- J

b~ Suluric acid Sulfated oils and fatty acids esters .
~0 R-CH~X-C \ Sul~ated es~ers lSo3 OR' ~0 R-CE3-X C Sulfated amides ¦ \ NHR' R-COO-CH2-CH-CH2-OSO3 Sulfated fatty acid monoglyce~ides ¦ and others OH

R-CONH-X-oS03 Sulfated ratty acid alkyloamides R-O-X-OS03 Sulfated ethers c) Alkylsulfonates R-CH-R' Si~ple alkylsulfonates S03 ~
CH2-COOR \ Sulfosuccinic acid esters R~OO-X-S03 R-fON-~-S03 - ~ Alkylsulfonates with intermedi.ates R' ~ members R ~ -O-X-S03 d) Alkylarvlsulfonates R' - ~ Alkylnaphthalenesulfonates R ~ O ~ Alkylben~enesulfonates _ 14 -~.: .......

e) Surface activ~ agents with less custGmary anionic groups r ~ 11 ~ Alkylp~osphates (various kinds) ~ \O~
Salts of alkylben~enephosphonic acids Cationic surface-active agents a) Amine salts ~
+ . \

+ ¦ Primary, secondary and tertiary R-NH2-R ' ,~
~ am~.ne salts R-NH-R' R-COO-X-NHR2 ~ Primary, secondary and tertiary . .~ amine salts with intermediate + members b) Quaternary ammonium salts ~' (Also wi.th intermediate members, .
R~N~-R' as in the case of amine salts) ~, 7~

c) Phosphonium salts d) Sulfoni~ salts R-P -R' and R-S~
1 lt Amphoteric surface-active agents . .

I
R-~X-C00- Betaines 1~ - - . . ' R-~X-0-503 Sulfate-betailles Non-ionic surface-active agents a~ Ethylene oxide adducts R (o-cH2-cH~ -oH Alk~ polyethylene glycols _ 16 -~ ~ , 9'7~

R~ (O-CH2-CH2)n-OH Alkylphenyl-polyethylene glycols .=~, ( 2 2)n Acyl-polyethylene glycols H-(O-CH2-CH2)n~(0-CH-CH2)m~(0-CH2CH2)n-OH Oxethylated poly-CH3 propylene glycols b) Further non-ionic surface-active agents R-COO-CH -CH-CH -OH Fatty acid monoglycerides OH

R-COO-C6H1104 Anhydrous sorbitol mono-fatty acid esters R-CONH-X-OH ¦
R-CON-X-OH ~ Fatty acid alkylolamides X-OH J

R-COO-cl2H2l010 Sucrose mono-fatty acid esters 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, polyhydroxy-alkyl monoester, of fatty acids and the like. The following may be mentioned 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 i.~

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polyhydro~yalkyl monoesters o~ fatty acids such as sorbi~an monooleate (Span 80).

The reduction of 2-nitro-2'-hydro~y-5'-methyla~o-benzene was carried out in an ~lkaline aqueous isopropanol solution employing sufficient sodium hydro~ide to convert the water-insoluble azobenzene intermediate into ~he cor-responding water-soluble sodium phenolate salt. ~ hydrQge-n~tion catalyst comprising molybdenum-promo~ed Raney nickel was used and the reduction and cyclization effected at a hydrogen pressure of from about 1 to about 5 7 atmosphe-res at temperatures from about 20C to about 100C, with a recovery o~ pure product in yields in the order of up to 80%.
However, higher pressures up to about 66 atmospheres may be used with equivalent results.

The reduction of 2-nitro-2'-hydroxy-3',5'-di-tert-amylazobenæene was carried out in an isopropanol/
diethylamine solution with a hydrogenation catalyst com--prising molybdenum-promoted Raney nickel~. The reduction and cyclization was effected at a hydrogen pressure of rom about 1 to about 5.7 atmospheres at ternperatures rom about 20C ~o about 100C, with a recovery of pure product in yields in the order of up to 78%. However, higher pressures up to about 66 atmospheres may also be used with equivalent results. Using the same conditions noted above, the reduction of 2_nitro-2'-hydroxy-SI-.methylazobenzene was carried out in a _ 18 -7~

tolu~ne/methanol/diethylamine solution with a hydrogenation catalyst comprising molybdenum-promoted Raney nickel with a recovery of pure product in yields in the order of up to 85-~0%.

The preferred catalysts which are employed in the process of this invention for effecting the reduction o o-nitroa~obenzenes to for~ 2-aryl-2H-benzotriazoles comprise promoted nickel catalysts.

While niclce]. hydrogenatiorl catalysts are generally useful in this reaction, so~e such ca~alysts are more selec-tive than others. Unpromoted Raney nickel is an effective catalyst in the cyclic reduction of the 2-nitroaæobenzene intermediates of this invention, but unless care i.s ~aken to control the amount of hydrogen absorbed excessive hydrogena-tion can occur with normal Raney nickel to yield undesired by-produc~s o ~he desired 2-aryl-2H-benzotriazoles Fartuna~.ely, it was found that selèctivity of the nickel catalysts can b~ favorably affected by ~he use of certain promoters. A molybdenum-pr~loted Raney nickell avai-lable as a 50% aque¢us slurry as Raney No.30 from W.R.Grace,is particularly e~fective in catalyzing ~he reduction cyclization of the substituted o-nitroazobenzenes to the co~responding 2-~ryl~2H-benzotria~oles in high yields and purity in al~aline solu~ions. Small amounts of catalyst axe _ 19 -`7 7~

required to effect the desired reaction with quantities of molybdenum-promoted Raney nickel as low as 0.01 mole to 0.03 mole/mole of o-nitroazobenzenes to be reduced being used. More catalyst can be used, but using amounts over 0.5 mole/mole of the o-nitroazobenzene is generally neither needed nor economically attractive.

While Raney nickel promoted by molybdenum is parti-cularly preferred as a catalyst in the process of this invention, other metals are also useful in promoting Raney nickel to being a catalyst for this process although not necessarily with equivalent results. Among such promoters are chromium, zirconium, iron, copper and silver. Chromium promoted Raney nickel gave results nearly equivalent to those obtained with molebdenium promoted catalyst in same cases.

Using these promoted nickel catalysts, reduction of the o-nitroazobenzenes to the corresponding N-oxy deri-vatives goes readily, but the subsequent reduction to the 2-aryl-2H-benzotriazoles is considerably more difficult.
Therefore to carry out the process of this invention in a practical fashion, it is often expedient but not essential to add roughly half of the total catalyst used as fresh catalyst at the start of the reduction of the N-oxy deri-vatives, i.e. halfway through the total reaction cycle.

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As hereinbefore stated, the reduction is e~ected at reducin~ co~ditions including a temperature wi~hin the range of from about 20C to about 100C, a pressure ranging from about 1 to about 66 atmospheres and with suf~icient aqueous alkaline solution to convert the hydroxy-substituted o_nitroazcbenzPnes into their cor-~esponding water-soluble or water-dispersed alkaline pheno-late .salts. The water soluble alkaline phenolate saits are prepared by adding the appropriate hydroxy-substituted o-nitroazobenzQne to an aqueous alkaline solution of sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, ammonia or th.e like. The preferred alkaline solution comprises from ak,out 5 to about lS~ by ~lei~t sodium hydroxide in water. When using this aq-~eous alkaline solution, it is possible at the end of the reduct.ion and cyclization reaction to remove the ~olybdenum-promoted Raney nickel catalyst by filtration for.
further recyclin~ if desired ~hile lea~ing thè desi.red 2-aryl-2H-benzotriazole product in aqueous solution as its alXaline salt in the case of the water-solub],e sa:lts.

In ~hè case of the water-dispersed alkaline pheno late sal-ts, it is necessary to have an appropriate dispersing a~ent also present in the system. In these cases the e-c~very of the catalyst requ~res precipitation of the 'crude 2-aryl-2H-benzotriazole product, separation by fi'ltration _ ~1 -~5~ Ji~

of the crude product contaminated by the molybdenum-promoted Raney nickel 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 molybdenum-promoted Raney nickel catalys~ 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.
A particularly preferred system involves the reduction of a 2-nitroazobenzene whose alkaline phenolate salt is water insoluble by dispersing the potassium phenolate salt in a medium comprising aqueous potassium hydroxide and a water immiscible hydrocarbon such as Amsco mineral spirits in the presence of a wetting agent such as sorbitan monooleate and a molybdenum-promoted Raney nickel catalyst.
As hereinbefore stated, the reduction may also be effected at reducing conditions including a temperature within the range of from about ~0C to about 100C, a pressure ranging from about 1 to about 66 atmospheres and with sufficient aqueous alkali/alkanol solution to convert the hydroxy-substituted o-nitroazobenzenes into their corresponding soluble ~0 alkaline phenolate salts. The soluble alkaline phenolate salts are prepared by adding the appropriate hydroxy-substituted o-nitroazobenzene to - 2~ -~ ..
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anaqueous alkali/alkanol solution containing sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, ammonia or the like with an alcohol. Any water-miscible alcohol can be used such as methanol9 ethanol, isopropanol, methyl cellosolve, n-but-anol and the like. For reasons of economics, ease of operation and availa-bility, isopropanol is preferred. The alkali/alkanol solutions preferably comprise a mixture of sodium hydroxide/water/isopropanol in a ratio by weight of from about 30/1000/30 to about 70/340/300 and preferably of from about 60/340/300 to about 60/440/200 for approximately each mole of the o-nitroazobenzene reduced. When using this aqueous alkali/alkanol solution, it is possible at the end of the reduction and cyclization reaction to remove the catalyst by filtration for further recycling if desired while leaving the desired 2-aryl-2H-benzotriazole product in solution as its alkaline salt.
Although a preferred solvent system for many of the 2-aryl-2H-benzotriazoles of this invention is aqueous alkali/isopropanol, other water- miscible organic solvents can also be used advantageously in this process. Such water-miscible organic solvents include hydrocarbons and ethers such as dioxane, tetrahydrofuran, 1,2-dimethoxyethane, 1,2-di-ethoxyethane, benzene, toluene, xylene or mesithylene and the like, such soIvents are particularly efective in aiding in dissolvi.ng the ~ore difficulty sol~ble hydro~y-s~bstituted o-nitroaæobenzenes and their co~xesponding alkaline phenolate salts where the sub~ti-tuents Rl, R2, R3, R4 and R5 tend to deter facile solubility in the alkaline aqueous organic me~lia of ~his process.

In another variation or this process, the lnor-ganic alk~li used to prepare the aqueous a].kali solutions used in the alkaline aqueous organic media of this in~ren-tion may be replaced by water-miscihle orr~anic amines.
Such amines not only provide the alkaline am~ience needed for the red~lctive cyclization of the o-nitroazobenzenes ~
the corresponding ~-aryl-2H-benzotriazoles, but also aid in the dissol~ing of the more difficultly soluble members of said o-nitroazobenzenes and said ~-aryl-2H-benzotriazoles in ~he reaction media. Thus, the alkaline aqueous or-ganic medium use~ul in this invention may comprise water cont~inin~ a wa~er-miscible or~anic amine in ~he presence or absence of a water-misc-lble alkanol t)r ether described previously Such water-lrlisci.ble amines may include primary~
sec.ondary or ter~iary al:iphatic ~mines especially with alkyL
groups o~ 1 ~o 4 carbon atoms, morpholine, p:iperidine, pipera-zine, guanidine, pyrrolidine, ethanolamines and the like. The s~mpl.e aliphatic amines are pre~erred such as diethylamine or n_propylamine.

~S9~7 o9 ~ s herei.nbefore stated, the reduction may be par~i~
cularly well effected at reducing conditions including a tem perature within ~he range of -Crom about 20C to about 100C, a pressure ranging from abou~ 1 ~o about 66 atmospheres wherein the o-nitroazobenzene intermediate b~ing reduced is dissol~ed in an ~rganic alkali.ne med-ium.Such a medium may comprise a water-miscible alkanol and~or e~her plus an organic amine, a hydrocarbon plus an organic amine or a hydrocarbon plus a water-mi.scible alkanol and/or ethex plus a orga~ic ~,line.

Water-miscible alcohols of use in this invention include methanol, ethanol, isopropanol, methyl cellosolve (2-methoxyethanol), n-butanol and the like. When an alkanol is used alone with an organic amine, for reasons o~ economics, ease of operation and availabilitv, isopro~
panol is prefexred. The concentration of the o-nitroa20--benzene ~eing hydrogenated in the alcohol, such as isopropanol, ranges rom 15- to 30% by weight.

Othex water-miscible organic solvents can also be used advantageously in comb.ination with an organic ~ine. Such water-miscible solvents include ethers such as dioxane, tetrahydro~ur~n, 1,2-dimethoxyethane, 1,2 dièthoxyethane and the ].ike. O~her solvents found _ 25 -~5~7 ~ 5~
useful in this process include the trialkylphosphates such as triethylphosphate or tributylphosphates and the like.

Mixtures of water-miscible alcohols and ethers or hydrocarbons or trialkylphosphates can also be used in this process along with an organic amine.

In another modification of the solvent system operable with the present process, the o-nitroazobenzene intermediate may be dissolved in a hydrocarbon solvent~
with or without the presence of a water-soluble alcoho:L
or ether, containing a water-soluble organic amine.
The hydrocarbon solvents may be aromatic, such as benzene, toluene, xylene and the like, cyclohexane, aliphatic, such as hexane, heptane, and the like, petroleum, mineral spirits, medium fraction petroleum ether and other related petroleum solvents and mixtures thereof. A particularly useful solvent combination is toluene containing about 25 to 35~ by wei~ht methanol.

The concentration by weight of o-nitroazobenzene intermediate used in any of the solvent systems of this invention can range from dilute solutions in the range of 5-10~ to concentrated solutions in the range of 20-30%.
For reasons of economy, the more concentrated solutions are preferred.

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~: :

, '~

P~nother critical part of the solven~ system is ammonia or an organic amine in order to provide a strongly alkaline milieu in which the reduc~ive cyclization reacti.on can occur. From 1.0 to 3.~ moles of amine/mole of the o-nitroazoben~en~, preferably from 1~5 to 2.5 mGles of amine/mole of the o-nitroazobenzene and most prel-era~ly from 1.7 to 2.~ moles of amine/mole of o-nitroazobenæen belng reduced axe required. Any organic, strongly alkaline amine can be used. It is preferred to use water-miscible amines such as pri~ary, secondary or tertiary aliphatic amines preferably ~.th alkyl groups of 1 to 4 carbon atoms, n-bu~yl-amine, ethanol~mine, diethanolamine, triethanola~nine, isopro-pylc1mine, pyrrol;.dine, piperazine,guanidine, morpholine, piperidine and the like. It is preferable that the amine used forr~ a water-soluble hydrochloride or sulfate salt in order to facilitate the separation of the amine com-pollent from the orga.nic solution of the desired 2-ary].-~H-benzo~ria~ole and to aid in the isolati.on of a pure desired product from sai.d solu~ion. The amine is regen-erat.ed fr~ its acid salt and recycled in the reaction system. For reasons of economics, ease of operation and av~ilability, .~orpholine, piperidine and the lower dialkyl-amines J such as diethylamine, dimethylamine, di-n-propylamine and the like are preferred. Particularly pre-ferred is diethylamine or n_propylamine.

- ~7 ~

Isolation of a product in yood yield and acceptable purity is another feature of this invention. The aqueous alkali or alkaline aqueous organic solution of the desired hydroxy-substituted 2-aryl-2H-benzotriazole salt, preferably the sodium salt, is acidified with aqueous mineral acid, preferably sulfuric acid or hydrochloric acid, to a pH of 10 or below in order to precipitate the desired hydroxy-sub-stituted 2-aryl-2H-benzotriazo].e as a crude product in yields in the range of 75 to 90%. The crude product may be further purified by one of several procedures to ~ive purified pro-ducts of high purity in yields in the range of 70 to 80%.
variety of trace by-products areformed during the reduction of o-nitroazobenzenes~ These include the corresponding o-aminoazobenzenes, o-aminohydrazobenzenes, o-phenylenediamine, anilines, aminophenols and 1,2,3-benzotriazoles. Most of these by-product impurities are removed by an acid, pre-ferably sulfuric acid, wash followed by an alcohol, preferably isopropanol, wash and finally a water wash of crude 2H-benzotriazole product. Alternatively, the crude product may be dissolved in an organic solvent, such as toluene, and the impurities extracted by an aqueous acid solution, and the product isolated then from organic solution by con-ventional procedures.

While the reductive cyclization reaction does not occur in the absence of a strong alkaline milieu such as is provided by one or more of the organic amines described above, it is often expedient to run the instant process where the organic solvent consists essentially entirely of one of the organic amines alone. In such a case, an excess molar quantity of amine relevant to the o-nitroazobenzene is always present. This solvent system has the advantage of sim-plified solvent recovery at the end of the reaction since mixtures of solvents are not involved. Amines providing a particularly good balance of base streng~h, solvent character, physical properties, ease of handling, availability and opera-bility in the instant process include n-propylamine, diethyl-amine, triethylamine, isopropylamine, n-butylamine, dibutyl-amine, tert-butylamine, amylamine, morpholine and the like.
Using an organic amine as the organic solvent for this process, yields in the order of 70 to 90% can be obtained.

~ ,,.

~ .

'7~11 Isolation of a product in good yield and high purity is a particularly important feature of this invention when an alkaline organic solution of the desired hydroxy-substituted 2-aryl-~H-benzotriazole is extracted with sufficient aqueous mineral acid, preferably sulfuric acid or hydrochloric acid, to remove the amine and most impurities formed during the reaction. A variety of trace by-products are formed during the reduction of o-nitroazobenzenes. These include the corres-ponding o-aminoazobenzenes, o-aminohydrazobenzenes, o-phenylenediamine, anilines, aminophenols and l,2,3-benzo-triazoles. Most of these by-product impurities are removed by an acid, preferably hydrochloric or sulfuric acid" wash.
An advantage of this process lies in the fact tha1 the desired product dissolved in the organic solvent, preferably isopropanol/diethylamine or toluene/methanol/diethylamine, can be separated from most impurities and the diethylamine by the aforementioned aqueous acid wash leaving the product dissolved in isopropanol or toluene. The isolation of a pure product generally requiring no further purification for commercial use is carried out by conventional crystallization procedures in yields in the range of 65 to 85%.

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-7~

type operation is used, a quantity of the hydroxy-substituted o-nitroazobenzene, water, sufficient alkali, such as sodium hydroxide, to prepare the water-soluble or water-dispersed alkaline phenolate salt along with the molybdenum-promoted Raney nickel catalyst 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 contens thereof are then heated, if needed, to the desired reaction temperature and maintained thereat with agitation until about half the theoretical amount of hydrogen is ab-sorbed, whereupon an additional amount of fresh molybdenum-promoted Raney nickel catalyst is added to the autoclave.
The reaction is then continued until slightly more than the theoretical amount of hydrogen is absorbed and the reduction reaction is complete. ~t 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 inert at-mosphere 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 desired hydroxy-substituted 2-aryl-2H-benzotriazole crude product, which may be optionally further purified by treatment with aqueous acid and recrystallization from an organic solvent.

In the case of the water-dispersed alkaline phenolate salts, the mixture is just brought to room temperature and acidified with mineral acid solution. The insoluble hydroxy-substituted 2-aryl-2H-benzotriazole crude product containing therein the molybdenum-promoted Raney nickel 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 des-cribed above.

The process of this invention may also be effected in a similar batch operation wherein the quantity of hydroxy-substituted o-nitroazobenzene is converted to its corres-ponding alkaline phenolate salt by dissolving in an alkaline aqueous organic medium, preferably in aqueous sodium hy-droxide and isopropanol. The process is thereafter carried out as described above for alkaline phenolate salts dis-solved in an aqueous alkaline solution.

In another batch operation, a quantity of the hydroxy-substituted o-nitroazobenzene, alkanol, such as isopropanol, amine, such as diethylamine, along with the catalyst, such as molybdenum-promoted Raney nickel, is placed in appropriate apparatus such as a shaking or stirred autoclave. In other cases the organic solvent will comprise a hydro-carbon solvent, su¢h as toluene or mineral spirits, a wa~er-soluble a'~:anol, such as methanolt and an amine, such as diethylamlne. Hydrogen is pressurized in until the desired initial pressure is reached. ~he autoclave and the ~ontents thereof are then hea~ed, if needQd, to the desirea xeaction temperature and maintained thereat with agitation until about hal~ the theoretical amount of hydrogen is absorbed, whereupon an additional amount of fresh molybdenum~
promoted Raney nickel catalyst is added to the autoclave.
Tne reaction is cont:inued until slightly more than the theoretical amouIlt of hydrogen is taken up an~ the reduction xeaction is complete. At the end of this time the excess pressure is vented, the warm alkaline or~anic solution is subjected to filtration, preferably under an inert atmos-phere such as niirogen ox argon, to rernove the catalys~.
The solution, still ~arm, is extracted with mineral acid solution to remove impurities and the diethyla~ine to leave the de~ired hydroxy--substituted 2-aryl-2H--benzotriazole product in organic solution from which it may be isolated in pure form by crystallization.

It is also contemplated w~thin the scope of this ~nvention that the preparation of the ~-axyl-2H-benzotria zoles by the reduction and cyclization of o-ni-troazobenzelles m~y a3so be ef~e~ted in a continuous manner, although not necessarily with equivalent xesults. For example, when a continuous type operation is used, the h~droxy-substitllted ~ 33 .

" ' : ' o~nitxoazobenzene starting ma~erial is premixed ~ith, and discolved or dispersed in an alkaline medlum, said solution ox dispersion fed continuously to ~ reaction zone ~Jhich is maintGined at -the proper operating conditions of temp~
erature and pressure and which contains the hydrogenation catalyst. Means are provid~d to add additional catalyst beore the second half o the reaction cycleO

}Iydrogen is pressurized into the reaction zone by ~ separate means. A~ter desired residence t~me, tne reactor effluent is continuously discharged ancl the ef-~luent solution is acidified to isolate the desired pro~uc'...
Due to the nature of the catalyst enployed, a parti.cularly a~fective continuous type of operati.on comprises a fixed be~ o~ catalyst subjected to either an upward or downward flo~7 of the reaction solution or dispersion, I~' it is desirable to carry out the reduction as a two step process with a different operating temperature for each s~ep, t~o reaction zones in series each operaiing at the preferred temperature range for the specific reduction step involved may be used.

The reduction of o-nitroazobenzenes to the cor~
r~sponding 2-aryl-2E~-benzotrlazoles is a t~o-step pxocess as outlined below~

- 3 OEI
~ N-N ~_ ~ ~ R

R2 N2 ~ -~ /

OH

R'' ~ ~ . ~

jstep 2 ~ J
OH

R X\ / ~ \N ~ ~ ~

Step 1 -- The reduction of the o-nitroazobenzene to the N-o~ybenzotriazole derivative proce~ds rapidly and exother-mically even at low temperature under the pxocess conditions this .invention.

_ 35 -Step 2 ~ The xeduction of th~ oxyben~o~riazole intermediate to the cvrresponding 2-aryl-2~-benzotriazole prod~ct goes more slowly. This reduction c~.n be ~reatly expedited by adding more catalyst, raising the temperature, increasi~g the hydrogen pressure or by combination of these factors.

Generally, the reaction ceases when t~e N-oxy in-termediate is completely reduced to ~he corresponding 2-aryl-2H-ben~otriazole makin~ for facile control of this catalvtic hydrogenatiol~ process. Hot~ever; with some highly substituted benzotriazoles, reduction should be stopped wnen the appropri-ate amount of hydrogen has been absorbed and reacted to preven~
urther reductive cleavage of the desired 2-aryl 2H-benzotri ~oles prepared.

Speci~ically, the instant invention provides an impxoved process for production of compounds having the formula I

~fN ~ ~ ~ - R4 ~2 N
- ~3 ~ 7~

wherein Rl is hydrogen or chloxine, R2 is hydrogen, chlorine, lower alkyl of 1 to ~
carbon atoms, lower alkoxy of 1 to 4 earhon atoms, c~rbo-alkoxy of 2 to 9 caxbon atoms, carboxy or S03H, ~ 3 is alkyl of l to 12 carbon atoms, alkoxy of to 4 earbon atoms, phenyl, phenyl substi.tuted with alkyl groups, said alkyl groups having 1 to 8 carbon atorns, eyclo-alkyl of 5 to 6 carbon atoms, caxboalkoxy of 2 to 9 carbon atoms, chlorine, carboxyethyl or arylalkyl of 7 to 9 earbon atoms, 3 ~ 4 is hydro~en, lower alkyl of 1 to 4 ca.rbon atoms, lo~er alkoxy o 1 to 4 carbon atoms, chl.orine or hydroxyl, and R5 is hydrogen, alkyl of 1 to 12 earbon atorns, ehlorine, cyeloalkyl of 5 to 6 earbon at.oms or`arylalkyl of 7 to ~ carbon atoms.

R2 can be lower alkyl of 1 to 4 carbon atoms such as methyl, eth~li or n-butyl. R2 can also be lower alkoxy o 1 to 4 car~on atoms such as methoxy, ethoxy or n-bu toxy . R2 ean also be carboalkoxy o.f 2 to 9 carboII atom~ such as carbo-metho~y, carboethoxy, or earbo-n~oetoxy.

R3 ean be alkyl of 1 to 12 earbon atoms sueh as methyl, ethyl, see-butyl, ~ert-bu~yl, amyl, tert-oc,yl or n-dodecyl. ~3 can also be alko~y 03- 1 to 4 carbon atoms such ~s methoxy, ethoxy or n-butoxy. R3 is also phenyl substitute~.
with alkyl groups, said alkyl groups having 1 to 8 carbon atoms sueh as meth~ ert-butyl, tert-amyl or tert-oetyl. R3 ean also be eyel~alkyl of 5 t.o 6 carbon atoms sueh as eyelope~tyl or eyelohexyl. R3 is also carbo~lkoxy of 2 to 9 earbon atoms sueh as ear~omethoxy, earboethoxy, earbo-n-butoxy or earbo-n-oetoxy. R3 is also arylalkyl of 7 to 9 earbon atoms sueh as benæyl, ~-methylbenzyl or a,a-dimethylbenzyl.

R~ ean be lower al~yl of 1 to 4 earbon atoms sueh as me~lyl r ethyl or n-butyl.

R4 ean also be lower alkoxy of 1 to 9 earbon atoms sueh as methoxy, ethoxy or n-butyloxy.

Rs ean be lo~er alkyl of 1 to12 carbon atoms such as methyl, see--butyl, tert-butyl,. tert-amyl or tert-oetyl or n-dodecyl.

R5 ean also be cycloalkyl of 5 to 6 carbon atoms sùeh as eyelopeiltyl or cyclohexyl. R5 is also aryla7ky~ o, 7 to 9 carbon atoms such 2S benzyl, ~ methylbenz.yl or a,a-dim~thylDen~yl .

Pre~era~ly R~ i.s hydrocJell.

- 3~ _ "

Preferably R2 is hydrogen, chlorine, lo~er alkyl of l to 2 carbon atoms, methoxy or carboxy.

Preferably R3 is alkyl of l to12 carbon ator,ls ~yclohexyl, phenyl, chlorine, ~-methylbenzyl or carboxyethyl.

Prefexably R~ is hydrogen, hydroxyl or methyl.

Prefexably R5 is hydrogen, chlorine, alkyl of l to 12 carbon atoms, cyclohexyl, ben~yl or u-methylbenzylO

~ lOSt preferably ~z is hydrogen or chlorine~

Most preferably R3 is methyl, tert-butyl., tert-amyl, tert octyl, sec-butyl, cyclohexyl, chlorine or c~rboxyethyl.

Most preferably R.4 is hydrogen.

Most preferably R5 is hydrogen, chlorine, methyl, sec-butyl, tert-butyl, tert-amyl, tert-octyl or ~-methylbenzyl.

The process involved the reduction of an o-nitroa~o~

benzene intermediate of the formula II

OH

R ~ ~ ~ ~ }I

_ 3~ -wherein Rl/ R~, R3, R4 and R5 are as described previously.

The starting o-nitroazobenzene lntermediates ~re prepared by coupling the appropriate o-nitrobenzenediazonium compounds of formula III

~) Rl ~ N-N X

- R2 ~ N02 III

wherein Rl and R2 are as described pre~iously and X is chlo ride, sulfate, or other anionic species, hut preferably - chloride~ with phenols of formula IV -~~

.
. .OH

R5 ~V

R

which couple in the ortho position to the hydroxy group~

The o--nitrobenzenediazoni~ compounds are in turn prepared by standard diazotizaiion procedures usiny sodlum nitrite in acid solutio~ with the corresponding o-nitro--anilines of formula V

~ 40 , ~ , ; ` .

~4~

1 ~ ~ NH2 R~ ~2 For i.llustration parposes some specific examples o~ compounds of formulas IV and V are listed. These ltems are generally available as items of commerce.

Comp~unds of Formula IV
.. ..

p-cresol 2,4-di tert-butylphenol 2,~-di-~ert~amylphenol 2,4-di-tert--octylphenol 2-tert-butyl-4-methylphenol

4-cyclohexylphenol 4-tert-butylphenol 4 -tel-t -amylphenol 4-tert-octylphenol ~,4-dimethylphenol 3 t 4-dimethylphenol 4-chlorophenol 2,4~dichlorophenol 3,4-dichlorophenol 4-phenylphenol 4~phenoxyphenol . - 4 :

, 4-o-tolylphenol 4-(4'-tert-octyl)phenylphenol eth~l 4-hydroxybenzoate n-octyl 4-hydroxy~enzoate 4-methoxyphenol 4-n~octylphenol 4-n-dodecylphenol resorcinol 4~(~-meth~-lbenzyl)phenol 2~(~-methylbenzyl)-4~methylphenol 2-cyclohexyl-4-methylphenol 4 -sec-butylpllenol 2-sec-~utyl-4-tert-butylphenol ~tert-butyl~4-sec-butylphenGl ~-carboxyethylphenol 2~me~hyl-4-carboxyet.hylphenol Preferably compounds of formula IV use~ul in this invention are p-cresol ~,4-di~tert-butylphenol 2,~-di-tert-amylphenol 2,~-di-~tert-octylphenol 2-tert-butyl-4-methy.lphenol 4~t.ert-o~tylphenol 4 n octylphenol ~ Z _ .

' ~-n-dodecylphenol xesorcinol 2 sec-butyl-4-tert-butylphenol.
2~ methylbenzyl)-4-methylphenol Compounds of Formula V

o-nitroaniline 4-chloro-2-niiroaniline ~ -dichloro-2-nitroaniline 4-metho~:y~2-nitroaniline ~-~nethyl-2-nitroanilin~
4-ethyl-~-nitroaniline n-butyl 3 nitro-4-aminobenzoate n-octyl 3-nitro-4-aminobenzoate 4-n-butoxy~2~.nitroaniline ~-nitro-4-aminobenzoic acid 3~nitxo-4-aminobenzenesul~onic acid Prefera~ly compounds of Fcnmula V use~ul in this invention are o-nitroaniline 4~chloro-2-ni.troaniline _ ~3 .

. . ; : ."
., - ,~
~ .
.
-- .
. . . . .

s~
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, carboalkoxy of 2 to 9 carbon atoms; R3 is alkoxy of 1 to 4 carbon atoms, phenyl, phenyl substituted with alkyl groups said alkyl groups have 1 to 8 carbon atoms, carbalkoxy of 7 to 9 carbon atoms, arylalkyl of 7 to 9 carbon atoms, alkyl of 4 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 solution. With such intermediates the use of the dispersing or wetting agents described previously is generally necessary in the process of this invention when an aqueous alkaline medium is employed.

The 2-aryl~2H-benzotriazoles have found wide use as dyestuff intermediates, optical brightener blue fluor-rescent agents and selective ultraviolet light absorbing stabilizers affording valuable protection for fibers, films, and a variety of polymeric structures subject to deterio-ration by ultraviolet radiation. These materials have become important items of commerce.

The 2-aryl-2H-benzo-triazoles are complex organic molecules which require careful synthetic procedures for their production in good yield and acceptable purity.

. ~

~s~7~

The present invention is concerlled ~Jith an im-pxoved process to prepare ultraviolet stabilizers ~hich are substit~l.ed 2-aryl-2H-benzotriazoles. These are dis-tinguished by a very slight absorpt,ion in visible ligh~ and very high astness to light in various suhstâs~rates. Par-ticularly valuable me~bers of ~hese stabi:Lizers are com--pounds having a free hydroxyl group in the 2~posi~ion of ~he aryl ~roup linked to the 2-nitrogen of the benzot~iazole and which are further substituted in the 3- and 5 or 4 and 5-positlons by lower alkyl groups and may be subs~i-tuted by a ch]orine in the S-position of the benzot:riazole nucleus.

l'he description, preparation and uses of these valuable su~stituted 2-aryl-2H benzotriazoles are further taught in the U.S. Patent N~ers 3,004,896, 3,055,89~, 3rO7~r5S5, 3,074,910, 3,189,515 aIld 3,230,194.

Paxticular advantages of the a proc~ass according t:o the instant invention in the alkaline organic reaction medium are the high purity of the desired triazoles, the high ylelds in relati~e'ly low reaction times, the possibility to recycle the rea~tion medi~u~ preferably after re,moving of the reaetion water and optionally after a distillat-ion step, The maintainance of the catalyst acti~ity which is lowered only in small clmounts, is a further advantage~ The catalyst can be recycled5 optionally ~ogether with smaLl _ 45 .

amounts, e.g, about 1~% by weight, o~ fresh catalyst.

The following examples are ~iven to illustrat-e the process of the present invention, but are not intended to limit the scope of ~he presen~ inven~ion in any manner whatsoeve-r, _ 46 -Example 1 ~
2-(2-Hydro~y-3,5-di-tert-amylphenyl)-2H-benzotriazole To a 1-liter,low pressure hydrogenation reactor were charged under nitrogen with the reactor held at 45C by external heating 79.1 grams (0.2 mole) 2-nitro-2'-hydroxy-3',5'-di-tert-amylazobenzene (97% pure) dissolved in a solution of 230 grams of isopropanol and 29.3 grams (0~4 mole) o~ di-ethylamine and 3.0 grams of molybdenum-promoted Raney nickel catalyst as a 50% aqueous slurry. This amount of catalyst was about 1.9% based on the azobenzene intermediate.
The reactor was flushed several times with hydrogen and then pressurized with hydrogen to 1 atmosphere. The contents of the reactor were agitated vigorously and hydrogenated at 43-41C until hydrogen uptake slowed, which normally occurred after 50-65% of the theoretical uptake of hy-drogen. The hydrogen ~tmosphere in the reactor was then vented and replaced with nitrogen. An additional amount of 6.0 grams of the molybdenum-promoted Raney nickel catalyst as a 50% aqueous slurry was then added to the reactor. This amount of catalyst was another 3.8% based on the azobenzene intermediate for a total amount of cata-lyst used of 5.7%. The hydrogen atmosphere was then reim-posed on the reactor. The hydrogen uptake again first in-creased, but eventually ceased when about 114~ of the theoretical uptake of hydrogen had occurred. Near the end of the reaction a~ 45C t the reaction mixture became thick as cr~rstals appeared in the system. The hydrogenat,ion reaction required about 4 hours for completion.

The n~7drogen atmosphere present in the reactor was again vented and replaced with nitro~en. The contents o~
the reactor were heated to 60-65~C ~o dissolve the crystals present. With ayitation continued, 81.5 yrams of Amsco mineral spirits were charged to the ~eactor. The contents of the reactor ~7ere then fil~ered under nitrogen to remove the molybdenvn~-promoted nickel catalyst dispersed therein~
The recovered catalyst was washed on the filter with two portions of 4 grams of isopropanol. This washed catalyst was then s~litable for reuse in another hydrogenation re-action.

The filtrate containing the desired produc-t in solution was reheated to 65C and then treated with 16Ci ~rams of 6~ aqueous hydrochloric acid (0.26 m,ole). The system was stirred for 10 minutes and then allowed to seLtle for another 10 minutes. The aqueous acidic laver was then separated rrom the organic solvent layer containing the desired product in solution. The aqveous layer was ex-tract~d twice with 30 grams each of Amsco mineral spirits ~hich were added to the oryanic solvent layer. The com~
bined organic solution was extracted twice a~ain with ~0 grams of 6% aqueous hydrochloric acld (0.14 mole).

- Cs8 _ .

The Amsco mineral spirit/isopropanol solution of the desired product was then vacuum distilled at 95C to remove about 2/3 of the Amsco mineral spirits ~about 90 grams). To the residue was added 110 grams of isopropanol and 7 grams of concentrated hydrochloric acid. The mixture was heated to 70C to form a homogeneous solution which was then cooled with stirring to 50C, seeded, held at 45-50C to permit crystalliz-ation of the desired product and finally, cooled to 0C. The desired product, 2-t2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole was isolated by filtration, washed with six portions of 20 ml each of cold isopropanol and dried in vacuum at 50C to yield 54.8 grams (78% of theory) of pure material requiring no further purification for commercial use.
When the above hydrogenation was carried out in a 50% solution of Amsco mineral spirits in isopropanol in the presence of one equivalent of diethylamine to the azobenzene intermediate, the yield of isolated product was 75%.

~' ~7~

E~rn}~ e 2 ?- (2-~ydro~y--3,5-di~tert-c~ vl~henyl~-2H-benæotr~azolP

To a 10-~allon s~ainless steel jacketed r~ctor fitted ~ith a radial turbine ayitator, temperature recorder^-controller, a hy~rogen delivery system so arranged that internal reac~or pressure wowld remain constant throughout the hydrogenation and a nitrogen safety sparging system, was added undex nitrogen 10 kg of isopropanol alld 1.76 kg ~24.0 moles) of diethylamine. The solutlon was heated to 50C and 4.6 kg (12.0 moles) of 2-nitro-2'-hydro~y 3',5'-di-tert-amylazobenzene (37.1 % pure) and 3.81 ~g of iso~
propanol were added under nitrogen. The mixture was stirred vigorously and heated to 50C or lS minutes under nitrogen. To the solution was then added 180 grams of a 50~ slurry in water o~ a mol~bdenum-promoted Raney nic~el cat~lyst (W. ~. Grace, Raney ~o. 30 grade) and 200 ml vf isopropanol. This is 26 catalyst based on the o-nltroazo-benzene intermediate in solution. The system ~as pressured with nitrog~n and cooled to 45C. The ni~rogen was ven~ed arld replaced b~ hyclrogen with a cylinder regula~or pressure of 3.5 kg/cm . The theoretical hydrogen press~lre drop for complete reaction is 17.46 kg/cm2.

The agitator speed was set a~ 400 rpm and the vessel held at 3 5 kg/cm~ and 45C. Reaction

5~ ~
~ v , ,~
.

7~
was continued until the pressure in the hydrogen cylinder dropped less than 5% of theory per hour or roughly 55 to 70 of the theoretical pressure drop. The first step of the reduction to the corresponding N-oxy compound was complete.
This required about 50 minutes.

The reactor was vented, pressurized with nitrogen, stirring stopped and vented again. A second batch of molybdenum-promoted Raney nickel catalyst ~360 grams of a 50%
slurry in water) and 2000 ml of isopropanol were added. This is 4% catalyst based on the original o-nitroazobenzene inter-mediate used. The system was again pressurized with nitrogen and then hydrogen to 3.5 kg/cm2 as before.
The reduction was continued with vigorous agitation until the hydrogen cyclinder pressure was constant. This required about 2 hours. The reaction mixture was stirred for another hour before venting and pressurizing with nitrogen.

The system was then heated to 60-65C with stirring for 10 minutes. Agitation was stopped and the catalyst allowed to settle for another 10-15 minutes. To this mixture was added 4.89 kg of Amsco mineral spirits.
The mixture was heated to 65C and stirred vigorously.

The contents of the reactor were then filtered under 0.7 kg/cm nitrogen pressure to remove the suspended molybdenum-promoted Raney nickel catal~st. The reactor and filter were washed with two 1.2 kg portions of isopropanol. The combined filtrate contains 17.75 kg of 2-(2-hydroxy-3,5-di-ter~-amylphenyl)-2H-benzotriazole as a 21% solution in Amsco mineral spirits/isopropanol. This corresponds to a yield of 3.71 kg of product (100%) or 88% of theory.

The material was isolated from this solution by con-ventional procedures as a product of high purity in a yield of 78%.

The catalyst recovered from the filter can be used again during the first step reduction of another batch of an o-nitroazobenzene to the corresponding N-oxy-2-aryl-2H-benzotriazole.

Example 3 2-(2-Hydrox~-3,5-di-tert-amylphenyl)-2H-benzotriazole Using the general procedure of Example 1, a number of runs were made to determine the influence of several variables on the preparation of the above noted compound.

In all cases the temperature was 45C, 2 moles of diethylamine per mole of o-nitroazobenzene intermdiate and

6% molybdenum-promoted Raney nickel catalyst were~!used.
With one designated exception, the catalyst was added in two portions of 2% for the first reduction step and 4~ for the second step.

'7~

Hydrogen Yield Purity Hydrogen Time Absorbed Isolated o-Nitro- Pressu~e Reaction Run % of Theory Product % Azobenzene (kg/cm Min. , A 116 78 100% 15 ~1.05) 360 B 116 78 (Tech~) 15 (1.05) 360 C 113 78 100% 645.-2_30.2 160 D 124* 75 100% 15 (1.05) 360 E 110** 72 97~ 15 ~1 05~ ___ i * Same conditions as Run A except different lot of catalyst used. The different lot of catalyst caused a faster uptake of hydrogen in Run D, but did not significantly change the yield of product.

** Same conditions as Run B except that the catalyst used in Run E was a total of 8% with 6% recycled from Run~B.
2% additional fresh catalyst was added at the beginning of the second step in order to increase the reduction rate.
Without the fresh catalyst, the reduction of the N-oxy compound was sluggish at atmospheric pressure.

There was no perceptible advantage of llsing 100%
pure recrystallized o-nitroazobenzene intermediate since excellent yields of desired product were obtained from technical intermediates.

The use of higher hydrogen pressure 4.2 kg/cm2 versus 1.05 kg~cm2 reduced the time required to carry out the reaction significantly.

Example 4:
2-(2-Hydroxy-5-methylphen~ 2H-benzotriazole To a 500 ml Parr shaker bottle was added 48.7 grams ~0.18 mole) of 2-nitro-2l-hydroxy-5l-methylazobenzene (95% pure), 66 grams of toluene, 28 grams of methanol and 26.3 grams (0.36 mole)Of diethylamine. The resulting slurry was agitated until dissolved. The flask was then purged with nitrogen and 3.0 grams of a 50% slurry in water of a molybdenum-promoted Raney nickel catalyst ~W.R.Grace, Raney No. 30) was care-fully added. This is 3.2~ catalyst based on the o-nitroazo-benzene intermediate. The bottle was placed on the Parr hydrogenation shaker apparatus. The bottle was pressurized first with nitrogen and then several times with hydrogen. The pressure was set at 3.5 kg/cm and agitation begun. The reaction mixture was heated to 45C and the hydrogen absorp-tion began as seen by a drop in hydrogen pressure. After the absorption of hydrogen slowed or stopped with a pressure drop of 0. 98-1.19 kg/cm , the bottle was vented and a nitro-gen atmosphere was reimposed. Another 3 grams of a 50~ water slurry of the molybdenum-promoted Raney nickel catalyst was carefully added to the bottle. This i5 another 3.2% catalyst based on the o-nitroazobenzene intermediate.

The bottle was replaced on the Parr shaker and a hydrogen atmosphere reimposed at 3.5 kg/cm2. The reaction mixture was then heated to 58-60C. The hydrogen pressure was maintained between 3.5 and 2.~ kg/cm2 throughout the second step reduction until the hydrogen absorption levels off. The total drop in hydrogen pressure was 2.17-2.31 kg/cm .
The total reaction time was 150-175 minutes. The system was vented and a nitrogen atmosphere reimposed for all subse-quent steps.

40 grams of toluene was added to the reaction mixture which was then heated to 70C to assure complete solu-tion of the desired product. The reaction mixture was filtered to remove the suspended nickel catalyst which couId by recycled in another hydrogenation run after washing with 40 grams of toluene, 40 grams of methanol and finally water.
The toluene and methanol washes were combined with the original filtrate. The toluene and methanol were removed by vacuum distillation at 60-65C using a thin film evaporator to yield a thick slurry. 100 grams of methanol was added to the slurry which was agitated until uniform. The slurry was held at 0-5C for 30 minutes and then filtered to yield 37.2 grams (91.9%) of crude product after being washed with 100 grams of methanol and dried.

The use of an equivalent amount o~ n-propylamine substituted for the diethylamine gave the above named product in iso-lated yield of ~8%.

Example 5:
2-(2-Hydroxy-5-methylphenyl)-2H-benzotriazole -Using the procedure of Example 4, 48.7 grams (0.18 mole) of 2-nitro-2'-hydroxy-5'-methylazobenzene (95% pure) was dis-solved in 125 grams of water and 16.2 grams o 50% sodium hydroxide solution ~0~202 mole). After purging with nitrogen, 3.0 grams of a 50% slurry in water of a molybdenum-promoted Raney nickel catalyst ~W.R. Grace Raney No. 30) was care-fully added. This is 3.2% catalyst based on the o-nitroazo-benzene intermediate. At the end of the first step of the hydrogenation after a hydrogen pressure drop of 0.98-1.12 kg/cm , an additional 3.0 grams of catalyst described above was added. The total amount of catalyst used for both steps of the hydrogenation was 6.4~ based on the o-nitroazobenzene intermediate used.

The total hydrogen absorption was seen by a hydrogen pressure drop of 2.45-2.66 kg/cm2 and the total reaction time was 290-340 minutes.

After the hydrogen was vented, a nitrogen atmosphere was reimposed and an additional 3.72 grams of 50% sodium hydroxide solution was added to insure complete solution of the desired product. The suspended catalyst was removed by filtration at 50C with the catalyst being washed with 15 grams of 10% sodium hydroxide solution and the 15 grams of water. The catalyst could be used in another hydrogenation run after further washing.
The combined filtrates were treated under a nitrogen atmosphere with a 70% aqueous sulfuric acid solution until the p~l was reduced to a value of 10. The crude product which precipitated was isolated by filtration and washed successively with lO0 ml portions of water~ isopropanol and again water. The product was dried in vacuo at 45-50C and was recovered in a yield of 24.9 grams (62% of theory~. The product could be further purified by conventional recrystallization procedures.
~ hen 0.5% by weight of the wetting agent sorbitan monooleate (Apan 80) was added to the hydrogenation system, the above named product was obtained in an 84% yield.

Example 6: ~5~7 2-(2-Hydroxy-5-methylphenyl)-2H-benzotriazole When using the procedure of Example 5, 48.7 grams (0.18 mole) of 2-nitro-2'-hydroxy-5'-methylazobenzene (95% pure) was dissolved in a solution of 9 grams of sodium hydroxide in 30 grams of water and 45 grams of isopropanol, and a total of 7.0 grams of a 50% slurry in water of molybdenum-promoted Raney nickel catalyst (W.R.Grace Raney No. 30) were added in two equal 3.5 gram portions at the start and at the half way point of the hydrogenation, the product 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole was obtained in really quantitative yield after removal of the suspended nic]cel catalyst by filtration and acidification of the filtrate to a pH value of less than 4 using aqueous sulfuric acid.

Example 7:
.
2-(2-H drox -5-tert-oct 1 hen 1)-2H-benzotriazole Y Y Y P Y

When using the procedure of Example 1 an equivalent amount of 2-nitro-2'-hydroxy-5'-tert-octylazobenzene is substi-tuted for 2-nitro-2'-hydroxy-3',5'-di-tert-amylazobenzene, the above noted product is obtained.

Example 8 5 Chloro-2-C2-hydroxy-3,5-di-tert butylphenyl)-2H-benzotriaiole ~ Yhen in Example 1, the 2-nitro-2'-hydroxy-3',5'-di-tert-amyl-azobenzene was replaced by an equivalent amount of 2-nitro-5-chloro-2'-hydroxy-3',5'-di-tert-butylazobenzene, the above noted product was obtained in a yield of 68.2%. The use of this nickel catalyst did not result in any cleavage of the chlorine moiety from the molecule and no trace of the corresponding hydrogenated compound was observed.
Example 9 5-Chloro-2-~2-hydroxy-3-tert-butyl-5-meth~lphenyl)-2H-benzotriazole ~ Yhen in Example 1, the 2-nitro-2'-hydroxy-3',5'-di-tert-amyl-azobenzene is replaced by an equivalent amount of 2-nitro-5-chloro-2'-hydroxy-3'~tert-butyl-5-methylazobenzene, the above noted product is obtained.

Example 10:
2-t2-hydroxy-3,5-di-tert-a_~E_enyl)-2H-benzotriazole When using the procedure of Example 1, 0.5% by weight of the wetting agent sorbitan monooleate Span 80 was added to the hydrogenation system, the above named product was obtained in a 75,2% yield.

Example 11:
2-~2-Hydroxy-3,5-di-tert-amylphenyl)-2H benzotriazole When using the general procedure of Example 1, the molybdenum-promoted Raney nickel catalyst was replaced by an equivalent amount of unpromoted Raney nickel and with all other variables kept constant, the above named product was obtained in yields that were essentially the same as those obtained under the same conditions using the molybdenum-promoted Raney nickel catalyst.

These data are summarizal in the table below.

2% Raney nickel catalyst Hydrogenation Total Product Run added in 1 portion Temperature C Yield %
~_ 1not promoted 48 64.6 2not promoted 38 56.2 3molybdenum-promoted 35-48 60.1 4molybdenum promoted 35-38 56.1 _ . . _ .

Example 12 ~-(2-Hydroxy-5-methylphenyl)_2H-benzotriazole -When using the procedure of Example 1, the 2-nitro-2'-hydro~J-3',5'_di_tert_amyla~obenzen~ was replaced by an equivalent amount of 2-nitro-2'-hydroxy-5'-methylazobenzene and a total of 9% molybdenum_promoted Raney nickel catalyst was used, ~he above narned compound was obtained in a 60~3% yield.

Examp e 13 2-(2-Hydroxy-~_me~hylphenyl)-2H-benzotriazole When using the procedure of Example 4, the 6.0 grams of 50%
slurry in water of molybdenum-promoted Raney nickel catalyst was replaced by 6.0 grams of a 50% slurry in water of a chromium-promoted Raney nickel catalyst and with all the chromium-promoted catalyst being added in one portion at the start of the hydro~enation~ the abo~e named product was isolated in a yield of 72%.

- ~1 `, : ' . ; ': , .

Example 14 ___ _ 2_(2_Hydro~y_3~5_di.tel-t_butylpherlyl)_2H_benzotriazole __ When using the procedure of E~ample 4 the 2-nitro-2'-hydroxy-S'_methylazobenzene was replaced by an equivalent amount of 2-nitro-2' hydroxy_3,5_di.tert_butylazobenzene and using a total of 4 grams of molybdenum-promoted Ranev nic~el catalyst~
the above named product was obtai.ned in a yield of 49.2%.

Example 15 ~-(2-Hydroxy-5-methylphenyl)-2H-benzotriazole _ _ _ _ _ _ ______ _ When using the general procedure of Examples 4. or S, the molybdenum-promoted Raney nickel catalyst was replaced by unpromoted Raney nickel catalyst and with other variables kept essentially constant, the abo-~e named product was ob~ained in yields that were essentially the same as with the molybdenum_ promoted Ralley nickel catalyst.

These data are su~narized in the table below.

un Raney nickel catalyst Method Hydrogenation Total Product of Temperature Yield ~/0 Example C
_ 1 molybdenum-promoted 5 45 - 60 72.0 2 not promoted 5 45 - 60 60.9 3 not promoted 4 55 70 Run 1: h~/o Catalyst in 2 porti.ons, Run 2: 9% Catalyst in 3 portions~
Run 3: 4% Catalyst in 1 portion.
_ 6~ -_xample 16 2-(2-~lydroxy_3,5 di-ter~-amylphenyl)_2H-benzotri2zole ____ __ When using the general procedure of Example 5, the 2~.nitro-2'-h~droxy_5'_metllylazobenzene was replaced by an equivalent amount of 2-nitro-2'_hydroxy_3',5'_di_ter~_amylazobenzene and the sodium hydroxide was replaced by an equivalent amount of potassium hydro~ide, the hydro~enation was run in an Amsco mineral spirits wate-- (40/60) medium containing 1% sorbi~an monooleate, Span 80, we~ting agen~ at a hydrogen pressure of 6 atmospheres for a total period o~ 8 hours The above named product was obtained in an isolated yield of 71.9%.

- Example l?

_ (2-Hydroxy-3,5.d ~tert-Dutylphe.nyl)-2TI_benzotr~azole When using the general procedure of Example 1~ a 22% by weight suspension of 2_nitro-2'-hydroxy_3',5'-di-tert-butylazobenzene ;n isopropanol/triethylamine (1/0~18) was hydrogenated at 45C
in the presence of a Raney nickel catalyst (6% by weight based on the azoben~ene intermediate) for ~ period of 13 hours, the above named compound was obtained in a 67% yield.

When the amount of catalyst above was increased to 20% by weight based on the azobenzene, the hydrogenation was cornpleted in 1.1 hour at 45C to give a 75% yield o product.

- ~3 ~

7'~

E-xample 18 _ _ 2-(2-Hydroxy_3~5_di.tert butylphenyl)-2H.-benzotriazole .

Using the general procedure 6, 35.5 grams o:E 2-nitro-2'-hydroxy_3',51_di_~ert_butylazobenzene was suspended in 100 grams of tributyl phospha~e, 50 grams of methanol and 4 grams of sodium hydroxlde. To the suspension was ~hen added

8 gr-ams of Raney nickel catalyst and hydrogenation was carrled out under 1 atmosphere of hydro~en a~ 45C ~or 7 hours. lhe catalyst was separated by filtration at 80. The above named product was obtained in the usual manner in a yield of ~5. 8~/o.

Example 19 2-(2-Hydroxy-3,5-di-tert-amylphenyl)_2H_benzotriazole _ _ _ _ _ _ ~hen in Examp:Le 6, the 2-nitro-2' hydroxy-SI_methylazobenzene was l~eplaced by an equivalent amount of 2-nitro-2'-hydroxy-3'~5'-di-tert-amylaæobenzene and a total of 4% catalyst was used, the above named prod~lct was prepared in nearly quanti-ta~ive yield..

~ 6~ _ Exæmple 20 _ 2-(2-Hydroxy_3 5 5-.di-tert amylphenyl)_2H-benzotriazole -When using the procedure of Example 1 the isopropanol and diethylamine were replaced by sufficient n-propylamine ~.o give a 29% by weight solution of the 2-nitro~2'-hydroxy.-3l~5'-di-tert_amylazobenzene intermediate in. the amine solvent~ the hydrogena~ion was carried out at 45C and 50 psia (3.5 kg/cm2) pressure, T~e excess amine solvent was removed by disti.llation and the above named product was obtained in a. yiel~ of 43.3%.

When the n-propylamine solvent above was replaced by a like weight of di~thylamine and the hyd.-cogenation was carried out at 15 psia ~1 atmosphere), the yield of the above named product was 40.8%.

Example 21 2-(2-H~droxy-5-methylphenyl)-2H-benzotriazole When using the procedure of Example 4 the toluene, met'nanol and diethylamine were replaced by sufficient n-propylamine to give a 29% by weight solution of the 2-nitro-2'-hydroxy-5l_methylazoben~ene intermed~ate, the above named product was isolated by removing most of the amine solvent by vacuum distillation and slurring the residue in methanol, The crude product was obtained in a yield of 88.4%.

~ 65 .
, A comparison of the effect of us~n~ various organic amines as sol~en~ and base for ~he preparation of ?~(2-hydroxy-5-methyl-phenyl).2H_benæotriazole using ~he above procedure is shown in the table below.

~nine Solvent Reacti.onYield o Crude Product Time %
Millutes ~~

diethylamine 210 59.0 n-propylamine 190 88.4 dibutyla~line 150 74.0 isopropylamine 170 84.0 tert-butylamine 180 79,0 triethylamine 165 35.5 n_butylamine 130 79.0 amylamine 200 82.0 morpholine 240 72.0 n-propylamine~
with 20% water 250 59.0 n_propylamine~
with 15% water 220 74.0 The presence of signifi.cant quantities oi water in the organic amine ~olvent reduces the yield of the benzotria201e product.

. ~ :

Claims (26)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the production of 2-aryl-2H-benzotriazoles of the formula I

( I ) wherein R1 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, chlorine, cycloalkyl of 5 to 6 carbon atoms or arylalkyl of 7 to 9 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 from about 1 atmosphere to about 66 atmospheres while mixed in an alkaline medium having a pH greater than 10 in the presence of a nickel hydrogenation catalyst, and recovering the desired 2-aryl-2H-benzotriazole.

2. A process according to Claim 1 wherein said catalyst is a promoted nickel hydrogenation catalyst.

3. A process according to Claim 2 wherein said hydrogenation catalyst is molybdenum-promoted Raney nickel or chromium-promoted Raney nickel.

4. A process according to Claim 3 wherein said hydrogenation catalyst is molybdenum-promoted Raney nickel.

5. A process according to Claim 1, wherein said o-nitroazobenzene forms a water-soluble alkaline phenolate salt, which further comprises carrying out the reduction and cyclization in an aqueous alkaline medium, isolating said nickel 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.

6. A process according to Claim 1 which further comprises, carrying out the reduction and cyclization in a water miscible aqueous alkali/alkanol solution, removing the nickel catalyst by filtration, lowering the pH of the alkaline aqueous organic medium to a value less than 4 to precipitate the desired product and recovering the desired 2-aryl-2H-benzotriazole.

7. A process according to Claim 1 which further comprises, carrying out the reduction and cyclization in a solvent system which comprises a water-miscible amine alone or in combination with a water-miscible solvent selected from the group consisting of an alkanol, ether, trialkylphosphate and hydrocarbon, removing the nickel catalyst by filtration and recovering the desired 2-aryl-2H-benzotriazole.

8. A process according to Claim 1 which further comprises, carrying out the reduction and cyclization in an organic solvent system consisting essentially entirely of an organic aliphatic or alicyclic amine or morpholine, removing the nickel catalyst by filtration, and recovering the desired 2-aryl-2H-benzotriazole.

9. A process according to Claim 4 wherein said alkaline medium is an aqueous alkali metal hydroxide solution.

10. A process according to Claim 4 wherein said alkaline medium is an aqueous alkali metal hydroxide/alkanol solution.

11. A process according to Claim 4 wherein said alkaline medium is an aqueous alkali metal hydroxide solution containing a waterimmiscible organic hydrocarbon and a dispersing agent.

12. A process according to Claim 4 wherein said alkaline medium is a solution of an aromatic hydrocarbon methanol and an organic aliphatic or alicyclic amine or morpholine.

13. A process according to Claim 4 wherein said alkaline medium is a solution of an alkanol and an organic aliphatic or alicyclic amine or morpholine.

14. A process according to Claim 4 wherein said alkaline medium is an organic aliphatic or alicyclic amine or morpholine.

15. A process according to Claim 4 for the production of a compound of formula I wherein R1 is hydrogen, R2 is hydrogen, chlorine, lower alkyl of l to 2 carbon atoms, methoxy or carboxy, R3 is alkyl of l to 12 carbon atoms, cyclohexyl, phenyl, chlorine, .alpha.-methylbenzyl or carboxyethyl, R4 is hydrogen, hydroxyl or methyl, and R5 is hydrogen, alkyl of 1 to 12 carbon atoms, chlorine, cyclohexyl, benzyl or .alpha.-methylbenzyl.

16. The process according to Claim 4 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-amyl, 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.

17. A process according to Claim 4 for the production of 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole which comprises reducing and cyclizing 2-nitro-2'-hydroxy-5'-methylazobenzene.

18. A process according to Claim 4 for the production of 2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotrizole which comprises reducing and cyclizing 2-nitro-2'-hydroxy-5'-tert-octylazobenzene.

19. A process according to Claim 4 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.

20. A process according to Claim 4 for the production of 5-chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole which comprises reducing and cyclizing 2-nitro-5-chloro-2'-hydroxy-3,5'-di-tert-butylazo-benzene.

21. A process according to Claim 4 for the production of 5-chloro-2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-2H-benzotrizole which comprises reducing and cyclizing 2-nitro-5-chloro-2'-hydroxy-3'-tert-butyl-5-methylazobenzene .

22. A process according to Claim 4 for the production of 2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole which comprises reducing and cyclizing 2-nitro-2'-hydroxy-3,5-di-tert-butylazobenzene.

23. 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 1 to 8 carbon atoms and chlorine;
comprising reducing and cyclizing the corresponding o-nitro-azobenzene 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 alkaline medium containing an alkali metal hydroxide as base and having a pH
greater than 10 in the presence of a nickel hydrogenation catalyst and recovering the desired 2-aryl-2H-benzotriazole.

24. A process as in Claim 23 in which the o-nitrophenylazohydroxyphenyl starting compound of Formula II is 2-(2'-nitro-phenylazo)p-cresol and the resulting benzotrizole compound of Formula I is 2-(2'-benzotriazolyl)-p-cresol.

25. 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 1 to 8 carbon atoms and chlorine;
comprising reducing and cyclizing the corresponding o-nitro-azobenzene 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 alkaline medium having a pH greater than 10 in the presence of a nickel hydrogenation catalyst and recovering the desired 2-aryl-2H-benzotriazole.

26. A process as in Claim 25 in which the o-nitrophenylazo-hydroxyphenyl starting compound of Formula II is 2-(2'-nitro-phenyl-azo)p-cresol and the resulting benzotriazole compound of Formula I is 2-(21-benzotriazolyl)p-cresol.