CA1234140A - Process for the preparation of n-substituted orthophenylenediamines - Google Patents

Abstract

Process for the preparation of N-substituted orthophenylene-diamines Abstract Reaction of azobenzenes with secondary alcohols in the presence of a ruthenium catalyst and a basic compound leads to N-substituted orthophenylenediamines.

Description

~3~

6-14580/~

Process for the preparat;on of N-substituted orthophenylene-diamines The present ;nvent;on relates to a one-stage process for the preparation of N-substituted orthophenylenediam;nes from azobenzenes and a secondary alcohol in the presence of ruthenium catalysts and a basic compound.

It is known from JO Organometallic Chem;stry, 31 ~1971) 275, that azobenzene with Ru3tC0)12 leadsO inter alia, to com-plexes containing N-phenylorthophenylenediamine. The free diamine can be obtained therefrom by reaction with LiALH4.

The object of the present invention is to provide a one-stage, catalytic procPss for the preparation of N-substi-tuted orthophenylened;amines ;n wh;ch inexpens;ve and easily accessible starting substances can be used.

The present invention relates a process for the preparation of orthophenylened;amines of the formula I

R

2 .~ N- - -R

in ~h;ch R is a hydrogen atom or a group R7R8CH-, in wh;ch :~3~

R7 and R~, independently of one another are unsubstituted or substituted alkyl, cycloalkyl or aLkoxyalkyl, or R7 and R8 together are -(CH2) n~ where n =2 to 12, and R1, R2O
R3, R4, R5, R6, R9, R10 and R11 independently of one another are each a hydrogen atom, halogen, carboxylate, alkyl, alkoxy, alkylthio, alkoxyalkyl, cycloalkyl, aryl or aralkyl, or in each case two adjacent groups of R1~ R2, R3, and R9 or R4, R5, R6, R10 and R11 are -CH=CH-CH=CH-, and mixtures of those compounds of the formula I in which R ;s a hydrogen atom or a group R7R8CH , which comprises reacting an azobenzene of the formula \o_ 9~ /R6 R ~ N=N~
~=-- O---~
R R~0 ~4 ;n wh;ch R1 to R6 and R9 to R11 are as defined above, w;th a secondary alcohol of the formula R7R8CHoH in the presence of a ruthen;um catalyst and a basic compound at temperatures of at least 120C.

R7 and R8 can be linear or branched alkyl or alkoxyalkyl with preferably 1 to 20, in particular 1 to 12, C atoms or cycloalkyl with preferably 3 to 10, in particular 3 to 6 ring carbon atoms. Examples are: methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert;ary butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, hexadecyl, octadecyl, 2-methoxyethyl, methyloxymethyl, ethyloxymethyl, hexyloxy-methyl, cyclopropyl~ cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl. R7 and R~ together can be, for example, dimethylene, trimethylene, tetramethylene or pentamethylene. In the -(CH2~-n group, n is preferably 2 to 8.

Examples of suitable substituents for the radicals R7 and ~3~

R8 are alkyl with preferably 1 to 6 C atoms, such as methyl, ethyl, propyl~ isopropyl, n-butyl, isobutyl, ter~-;ary butyl, pentyl and hexyl; alkoxy with preferably 1 to 6 C atoms, such methoxy, ethoxy and propoxy; and cyGloalkyL
w;th preferably 3 to 7 r;ng C atoms, such as cyclopropyl~
cyclopentyl and cyclohexyl.

0~ the radicals R1 to R6 and R9 to R11, in each case one of R1 to R3 and R9 and ;n each case one of R4 to R6 and R10 and R11 is preferably a hydrogen atom. R1 to R6 and R9 to R11 as alkyl radicals pre~erably contain 1 to 6, in particular 1 to 4, C atoms; as cycloalkyl rad;caLs preferably contain 3 to 6 ring C atoms; as aryl radicals preferably contain 6 to 12 C atoms and are, in particular, phenyl; as aralkyl radicals preferably contain 7 to 16 C
atoms and are, in particular, phenylmethyl or ~-phenethyl~
as alkoxy, alkylthio and alkoxyalkyl radicals preferably contain 1 to 6 or 2 to 6 C atoms and are, ~or example, methoxy, ethoxy, methoxymethyl or methoxyethyl; and as carboxylate are, for example, radicals o~ the formula -COORa, in which Ra is alkyl with preferably 1 to ~ C
atGms~ cyclohexyl or phenyl. R9 to R11 are preferably hydrogen atoms.

Examples of secondary alcohols are: isopropanol~ 2-hydroxy-butane, 2- or 3-hydroxypentane, 2- or 3-hydroxyhexane, 2-,

3- or 4-hydroxyheptane, 2-hydroxyoctane, cyclopropanol, cyclobutanol, cyclopentanol, cyclohexanol, ~-hydroxyethyl) benzene, diphenylhydroxymethane and 1,3-dimethoxy-2-hydroxypropane. The secondary alcohols are known or can be prepared by known processes.

Examples of suitable azobenzenes are: azobenzene, 4-methyl-azobenzene, 4,4~-dimethylazobenzene, 4,3'-dimethylazobenzene,

4~fluoroazobenzene, 4-fluoro-4'-chloroazobenzene, 3-bromoazobenzene, 4,4'- or 3,4'-dichloroazobenzene, 3,5-dichloroazobenzene, 3~5-dimethylazobenzene, 3,3'-, 4,4'- and 3,5 diethylazobenzene, , ~.~3~
_ 4 -4-methoxyazobenzene, 4-(methoxymethyl)-azobenzene, 4-phenyl-a20benzene, 3-(methoxycarbonyl)-azobenzene, 3-benzylazobenzene, naphthaLeneazobenzene, 4,4'-difluoroazobenzene, 3~3',5,5'-tetramethylazobenzene, 4-chloro-4'-methylazobenzene, 4-fluoro-4'-methylazobenzene, 4-methyl-4'-(ethoxycarbonyl~-azobenzene, 3,5-dichloro-4'-methylazobenzene, 3,3'-dimethylazobenzene and ~-methyl-4-methoxyazobenzene. The azobenzenes are like~ise compounds wh;ch are known or can easily be prepared.

Catalysts are preferably used in amounts of 0.001 to Z0, in particular 0.01 to 10 and espec;ally 0.01 to 5 mol%. These can be heterogeneous catalysts, for example ruthenium on a suitable support, such as charcoal, or, preferably, homogen-eous catalysts which are soluble in the reaction mixture.
Examples of homogeneous catalysts are compounds of ruth-enium, in particular salts the-reof w;th inorgan;c or organ-ic acids and complex compounds thereof. The complexes can be mononuclear or polynuclear and they can contain poly- -functional or, preferably, monofunct;onal ligands. Ex-amples of such l;gands are described in Advanced Inorganic Chem;stry~ 4th Ed;t;on, Verlag Wiley New York (1980~, pa~es 107 to 194. The compounds and complexes can be in any of the oxîdation levels o~ ruthen;um; they are preferably ;n oxidation level 0, 1, 2~ 3 or 4~

Suitable salts of ruthenium are der;ved, for example, from the following ac;ds: formic acid, acetic acid, benzoic acid, toluenesulfonic acid, phosphoric acid, sulfuric acid, per-chloric acid~ hydrofluoric acid, hydrobromic acid, hydriodic acid or, in particular, hydrochloric acid. The salts can also be employed in their hydrated form. Ruthenium tri-chlor;de tr;hydrate ;s particularly preferred~

Of the colnplexes, those with carbonyl ligands are parti-cularly preferred. An example is dodecacarbonyl-triruthen-ium. In a preferred embodiment of the process according to the ;nvention! the carbonyl complexes are formed, for ~34~

5 --example, from the abovementioned salts before or during the reaction by carrying out the reaction under a pure carbon monoxide atmosphere or wnder mixtures of carbon monoxide with an inert protective gas, for example nitrogen~ or a rare gas, such as helium or argon.

Other ligands are compounds with donor atoms~ for example ~, N, As, Sb, B;, O, S or Se, and anions of organ;c or in-organic acids. Examples are the arsines, stibines, bis-muth;nes and, ;n particular, the phosph;nes. Other ex-amples of l;gands are fluor;de, bromide, chloride, iodide, hydr;de, the tr;chlorotin(II) anion, d;methylsulfoxide, nitrosyl, the acetate anion and the acetonylacetate anion.
Part;cularly suitable ligands w;th trivalent elements of ma;n group five of the per;od;c table are the am;nes, phos-phines, ars;nes, stibines and b;smuth;nes, especially those with aryl radicals, for example phenyl, wh;ch can be sub-st;tuted by halogen (F or Cl~, C1-C4-alkyl or C1-C4-alkoxy.
Other rad;ca~s are alkyl with preferably 1 to 12 C atoms, cycloalkyl, for example cyclohexyl, and aralkyl, ~or example benzy~. Preferred ligands from th;s group are the phosph;nes. Examples are:

Triphenylphosphine, trito-to~uyl)phosph;ne, tri~p-toluyl~-phosphine, tr;~p-fluorophenyl)phosphine, tri(p-methoxy-phenyl)phosphine, tert.-butyld;phenylphosphine, tr;cyclo-hexylphosphine~ tetraphenyldiphosphine, triphenylamine and triphenylstibine. Phosphites are also su;table, especially those w;th aryl radicals, for example phenyl. An example is triphenyl phosph;te. The complexes can contain identi-cal or different l;gands. The complexes preferably conta;n phosphine and CO l;gands.

The complexes can be added as isolated compounds at the start of the reaction. It has proved advantageous to pre-pare the complexes before the start of the reaction from ruthenium compounds (for example their salts) by addition , :

~34L~

- 6 -of the l;gand-forming compounds, if necessary in a C0 atmosphere, and to cont;nue the process according to the invention by addition of the reactant.

Equimolar amounts or an excess of the ligand-forming com-pounds can be added~ The molar rat;o of ruthen;um com-pounds to l;gands ;s preferably 10 to 1, in part;cuLar 6 to 2.

In a preferred embod;ment of the process~ ruthenium com-pounds, espec;ally the;r hal;des, are used and the reaction ;s advantageously addit;onally carried out under a C0 at-mosphere.

Examples of suitable bas;c compounds are primary, secondary and, ;n particular, tert;ary am;nes. Examples of am;nes are methylamine, dimethylamine, tr;methylam;ne, cyclo-hexylam;ne, cyclohexyLdimethylamine, morpholine, N-methylmorpholine, piperidine, N-methylpiperidine, pyrro-lidineD N-methylpyrrol;dine and benzyLdimethylam;ne.

Preferred bas;c compounds are metal salts o~ carboxylic ac;ds, ;n particular the alkaline earth metal salts~ for example the calcium and strontium salts, and especially ~he alkali metal salts of carboxylic acids~ Preferred alkal;
metals are potass;um and, in particular, sodium and lithium~
Examples are: sodium bicarbonate~ lithium acetate, lithium prop;onate, l;thium formate, lithium benzoate, sod;um ace-tate and sod;um benzoate.

The bas;c compound ;s preferably used ;n an amount of at least 0.1 molX, based on the azobenzene o~ the ~ormula II, and up to stoichiometric amounts or more can be used.

The reactants are preferably employed in a molar ratio of secondary alcohol to azobenzene of at least 1 : 1. The ratio can be up to 8 : 1 or more~ in ~h;ch case an excess , .

- 7 ~
can simultaneously serve as the sslvent.

In a preferred embod;ment, the molar ratio of secondary alcohol to azobenzene is 1.0 : 1 to 2.5 : 1 and up to stoichiometric amounts of the basic compound are added.
Compounds of the formula I in which R is a hydrogen atom, frequently mixed with those compounds of the formula I in which R is an R7R8CH- group, are thereby obtained. The individual compounds can be isolated from the mixtures by customary methods. In another preferred embodiment of the process, the molar ratio of secondary alcohol to azobenzene is 3 : 1 to 8 : 1, in particular 4 : 1 to 6 : 1, and the amount of basic compound is 0.1 to 20 mol~, in particular 1 to 10 mol%~ In this case, pure compounds o~ the formula I in which R is the R7R8CH- group, or m;xtures containing predominantly such compounds together with compounds in which R ;s a hydrogen atom, are formed.

An inert solvent is advantageously also used. Polar aprotic solvents are particularly suitable. N-Alkylated acid amides are preferred. Furthermore, because of the reaction temperature, high-boiling solvents are preferred, so that the process can be carried out under normal pres-sure.

Examples of solvents are: hydrocarbons, such as benzene, toluene, chlorobenzene, dichlorobenzene, benzonitrile and tetralin, sulfones, such as tetramethylenesulfone, sulf-oxides, such as dimethylsulfoxide, tertiary amines, such as diphenylamine, cyclohexyldimethylamine and N-methylpiperi-dine, ethers, such as dioxane, d;ethylene glycol d;methyl or diethyl ether and tr;ethylene glycol dimethyl ether, and linear or cyclic N-alkylated acid amides, such as tetramethyl-urea, d;methylformam;de, d;methylacetam;de, d;ethylaceta-m;de, N-methylpYrrol;done, N-formylmorpholine, N-formyl-piper;dine and hexamethylphosphoric acid triamide, and esters of phosphoric acid or carbonic acid, for example ~.~3~
-- 8 ~
triethyl phosphate and propylene carbonate. Preferred sol-vents are d;ethylformamide, d;methylacetamide, N formylmor-pholine and, in part;cular, tetramethylurea and also 1,3-d;methyl-2-;m;dazolidone.

The process ;s carr;ed out in the apparatus customary for th;s purpose, by m;x;ng together the reactants, the cata-lyst, the basic compound and, ;f appropriate, a solvent and then warm;ng the reaction m;xture to the des;red reaction temperature. This is preferably 120 to 250C, in parti-cular 150 to 230C and especially 150 to 220C. The process can be carr;ed out under normal pressure or ;n-creased pressure~

The reaction products are isoLated in the customary manner~
for example by crystallization or d;stillation, ;f appro-priate after removal of the solvent~

N-Phenylated orthophenylenediamines (compound A) or those orthophenylenediam;nes which are additionally substituted on the second N atom by an R7R8CH group (compound B) are obtained in good y;elds and high purity from inexpens-ive starting substances ;n a s;mple manner by the process according to the invention~ Compounds A are use~ul inter~
mediates for the preparation of N-phenylbenz;midazoles, which act as leaf fungicides (compare Swiss Patent Speci-fication ~78,256). Compounds B can be used, for example, as antioxidants for gasoline (compare U~S. Patent Specifica-tion 3~290,376).

The following examples illustrate the invention in more detail. The yields are based on the azobenzene employed.
The following numbering ;n the diamines of the formula I is used to characterise the position of the substituents:

_ 9 ~ 3~

/3~ ~ H
il i_ ~6~ ~ \.6_ 5~

Example 1: 25 ml of tetramethylurea are ;ntroduced into a pressure tube and carbon monoxide is passed through, with stirring. 9.1 9 (50 mmol) of azobenzene, 7.67 ml (100 mmol? of isopropanol, 3.3 g (32 mmol) of l;th;um acetate dihydrate, 0.1308 9 of ruthenium trichloride trihydrate and 0.524 9 (2 mmol) of triphenylphosphine are addedu The tube is closed under carbon monoxide under normal pressure and the mixture is then stirred at 180C for 8 hours.
After removal of the solvent, the product is distilled under a h;gh vacuum and is then recrystallized from a m;x-t~re of 50 ml of cyclohexane and 50 ml of hexane. 3.9 9 (21.1 mmol) of N-phenyl-1,2-benzenediam;ne are obtained as white crystals of melt;ng point 79~6C~ correspond;ng to a y;eLd of 42% of theory.

Exampl_ 2: The procedure described ;n Example 1 ;s repeated, except that 11.51 ml (150 mmol) of isopropanol and 0.33 9 (3.2 mmol) of l;th;um acetate d;hydrate are used. After d7stillation, the crude product is chromatographed on s;l;ca gel ;n methylene chlor;de and is distilled again under a high vacuum. 4.0 9 (17.7 mmol~ of N2-isopropyl-N1-phenyl-1,2-benzenediam;ne are obtained as a yello~r liquid of boil;ng po;nt 118-Z2C/û.1 mm Hg~ correspond;ng to a yield of 35% of theory.

Examples 3-17~ The procedure described in Example 1 is re peated, except that 1Z.5 ml of tetramethylurea~ 4.55 9 (25 rnmol) of azobenzene, 0.0654 9 tO.25 mmol) of ruthen-ium tr;chloride trihydrate, û.262 9 (l mmol) of triphenyl~
phosph;ne and the amounts of ;sopropanol and sod;um ~23~

acetate (anhydrous) shown in the table are used. After a reaction time of 8 hours at 180~, the yields of the two products N-phenyl-1~2-benzened;amine (A) and N2-isopropyl-N1-phenyl-1,2-benzenediamine (B~ are determined by gas chromatography.

Example Isopropanol Sodium acetate Yield (X) No. (mmol) (mmol) A B
.

8 40 25 24 8

9 40 30 28 19 2~ 17 1~5 0 30 27 E~am~le 18: The procedure described in Example 1 is re-peated, except that 12.55 g t50 mmol~ of 4,4-dichloroazo benzene are used in place of the azobenzene. After distil-lation, the crude product is recrystallized from a mixture of 20 ml of cyclohexane and 5 ml of carbon tetrachloride.
2.55 g t10.1 mmol) of N1-t4-chlorophenyl)-5-chloro-1,2-benzenediamine are obtained as white crystals of melting point 92.3C, corresponding to a yield of 20% of theory.

19: The procedure described in Example 1 is re .
peated, except that 10.9 9 tS0 mmol) of 4,4'-difluoroazo-~3~
benzene are used in place of the azob~nzene. After distil lation, the crude product is chromatographed on silica gel in methylene chloride and dist;lled again under a high vac-uum. 4.2 g (19.1 mmol) o~ N~ -fluorophenyL)-5-fluoro-1,2-benzenediamine are obtained as a yellow liquid of boil-ing point 129-31C/0.1 mm Hg, corresponding to a yield of 38% of theory.

Example 20: The procedure described in Example 1 is re-peated, except that 10.5 9 (50 mmo~) of 4,4'-dimethylazo-benzene are used in place of the azobenzeneO After distill-ation, the crude product is recrystallized from 150 ml of n-hexane. 3.7 9 (17.5 mmol) of N1-(4-methylphenyl~-5-me~hyl-1,2-benzenediamine are obtained as white crystals of melting point 108.1C, corresponding to a yield of 35% of theory.

Example 21: The procedure described in Example 1 is re-peated, except that 12.55 9 (5a mmol) of 4,4'-dichloroazo-benzene are used in place of the azobenzene~ and 19.~ ml (250 mmol) of isopropanol and 0.13Z g t2 mmol) of lithium acetate (anhydrous) are used. After dist;ll3tion, and chromatography on si~ica gel in toluene, the product is recrystall;zed from 3~ ml of n-pentane. 6.6 g (22.1t mmol) of N2-isoProPyl-N1-t4-chlorophenYl)-5-chloro-1,2-benzene-d;amine are obtained as white crystals of melting poin~
70.7C9 corresponding to a yield of 45X of theory.

Example 22: The procedure described in Example 1 is re-peated, except that 10.9 g t50 mmol) of 4,4'-difluoroazo-benzene are used in place of the azobenzene. After dist;l-lation and chromatography on silica gel in methylene chlor-ide, the crude product is recrystallized from 50 ml of n-pentane. 7.3 9 (27.~ mmol) of N2-isoPropyl-N1-(4-fluorophenyl)-5-fluoro-1,2-benzenediamine are obtained as white crystals of melting point 81~ 3C, corresponding to a yield of 56X of theory.

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Example 23: The procedure described ;n Example 21 is re-peated, except that 10.5 9 t50 mmol) of 4~4'-dimethylazo-benzene are used ;n place of the azobenzene. After distil-lation and chromatography on silica gel in toluene, the product is distilled again~ 6.9 9 (Z7.2 mmol) of N2-isopropyl-N'-~4-methylphenyl)-5-methyl-1,2-benzenediamine are obtained as a yellow liquid of boiling point 128-32C/
0~1 mm Hg, corresponding to a yield of 54% of theory.

Examples 24-26: The procedure described in Example 1 is re-___ peated, except that 12.5 ml of tetramethylurea, 25 mmol of the azobenzenes shown in the table, 3.84 ml (50 mmol) of isopropanol~ 1.65 9 (25 mmol) of lithium acetate, 0.065 9 ~0.25 mmol) of ruthenium trichloride trihydrate and 0.262 9 (1 mmol) of triphenylphosphine are used. The results are shown ;n the table.

X~ N=N~ o--X + 2 i-PrOH ~ \
11 ~ I 11 ./~. /~
.. Il 1 11 i \j~- '\.~-(A) (B) i-PrOH = iso~ropyl alcohol Example No. X Yield (%) A
_____________._______________,________._____________________ 24 Cl 30 14 26 Me 35 24 _______________________________ ___________~___O__________ - 13 ~
Examples 27 28: The procedure described in Example 24 is repeated, but 4~55 9 (25 mmol) of azobenzene, 1.92 ml (25 mmol) of isopropanol and 1 mmol of the phosphorus ligand shown in the table are used. The yields are deter-mined by gas chromatography. N-Phenyl-1,2-benzenediamine (A), N1-phenyl-N2-isopropyl-1,2-benzenediam;ne (B).

Example No. Phosphorus ligands Yield (X~
A
_ _ _ _ _ ~ _ _ _ 27 tr;(p-tolyl)phosphine 20 0 28 tri~p-fluorophenyl)phosphine 7 0 _ . . _ ~

~a~ s 3~ : The procedure descr;bed ;n Example 27 ;s repeated, except that 9.b ml (125 mmol) of ;sopropanol, OrO66 9 (1 mmol) of lith;um acetate and 1 mmol of the phosphorus ligands shown in the table are used. The yields are determined by gas chromatography.

Example No~ Phosphorus ligands Yield (X~
A
____ ~
29 tr;(p-tolyl)phosphine 0 62 tritp-fluorophenyl)phosphine 35 3b Enamples 31-37: The procedure described in Example 1 is re~
peated, except that 4~55 9 (25 mmol) of azobenzene, 3.84 ml (50 mmol) of isopropanol, OnO654 9 (0~25 mmol) of ruthen;um trichloride trihydrate, O~Z62 9 (1 mmol) of ~ri-phenylphosph;ne and, according to the table, 12~5 ml of sol-vent and 25 mmol of base are used, at a reaction time of ~ hours at the temperatures shown ;n the table.

~L~34~

Example Solvent ~ase Temp. Yield ~X~
~C) A B
_ _ . _ _ 31 N~N-dimethylformamide LiOAc 180 26 6 32 N,N-dimethylacetamide lIOAc 1~0 34 22 33 N-formylmorpholine L;OAc 180 38 0 34 tetramethylurea LiOAc 160 338 tetramethylurea LiOAc 200 310 36 tetramethylurea NaHC03 180 27 9 37 tetramethylurea EDA* 180 205 . . _ _ _ . _ _ _ _ ~

*~DA: N-benzyldimethylamine Example 38: The procedure described in Example 1 ;s re-peated, except that 10.58 ml (100 mmol) of cyclohexanol are used ;n place of the isopropanol. After d;stillation and chromatography on silica gel ;n methylene chlor;de, the product is distilled again under a high vacuum. 3~38 g (18.4 mmol) of N-phenyl-1,2-benzened;amine are obtained as a yellow liquid of boiling point 139-41C/0.1 mm Hg, cor-responding to a y;eld of 37X of theory.

Example 39: The procedure described in Example 21 ;s re-peated, except that 5.1 9 t50 mmol) of azobenzene and 22.97 ml ~250 mmol) of 2-butanol are used in place of the dichloroazobenzene and ;sopropanol. After dist;llation, the crude product is separated on silica gel in toluene and the two crude products are d;stilled again. In addition to the N-phenyl-1,2-benzenediamine ~yield 30YO~ 1.49 9 (o.2 mmol) of N2-phenyl-N1-(2-butyl)-1,2-benzenediamine are ob-tained as a yellow liquid of boiling po;nt 139-142C/0.1 mm Hg, corresponding to a yield of 6% of theory~

Example 40: The procedure described in Example 39 ;s re-peated, except that 31.3 ml (250 mmol) of 3 hexanol are used in place of the 2-butanol~ N-Phenyl-1,2-benzenediamine '~

;s obta;ned as the product in a y;eld of 30% of theory.

Example 41: The procedure described in Example 39 is re~
peated, except that 9~8 g (50 mmoL) of 4-methylazobenzene and 19.15 ml (250 mmol) of isopropanol are used in place of the azobenzene and 2-butanol. After d;stillation and chromatography on silica gel in chloroform, the product is dist;lled again. 6.3 9 (26.25 mmol) of an isomer mixture consist;ng of 35% of N2-phenyl-N1-isopropyl-5-methyl-1,2-benzened;amine and 65X of N2-(4-methylphenyl)-N~-isopropyl-1,2-benzenediamine and having a boiling point of 12Z-28C/0.1 mm Hg are obtained, corresponding to a total yield of 53% of theory.

ExampLe 42: The procedure described in Example 10 is re-peated, except that 5.25 9 (25 mmol) of 2,2'-dimethylazo-benzene are used in place of the azobenzene. After 8 hours 8 OC and working up accord;ng to Example 19, 0.44 9 (1.73 mmol) of N1-(2'-methylphenyl)-N2-isopropyl-4-methyl-1,2-benzenediamine is obtained as a red oil of boil-ing point 120C/0.1 mm Hg.

Claims (13)

WHAT IS CLAIMED IS:

1. A process for the preparation of an orthophenylenediamine of the formula I
(I) in which R is a hydrogen atom or a group R7R8CH-, in which R7 and R8 independently of one another are unsub-stituted or substituted alkyl, cycloalkyl or alkoxyalkyl, or R7 and R8 together are -(CH2)n-, where n = 2 to 12, and R103 R2, R3, R4, R5, R6 R9 R10 and R11 independently of one another are each a hydrogen atom, halogen, carboxylate, alkyl, alkoxy, alkylthio, alk-oxyalkyl, cycloalkyl, aryl or aralkyl, or in each case two adjacent groups of R1, R2, R3 and R9 or R4, R5, R6, R10 and R11 are -CH=CH-CH=CH-, and mixtures of those compounds of the formula I in which R is a hydrogen atom or a group R7R8CH-, which comprises reacting an azobenzene of the formula (II) in which R1 to R6 and R9 to R11 are as defined above, with a secondary alcohol of the formula R7R8CHOH
in the presence of a ruthenium catalyst and a basic compound at temperatures of at least 120°C.

2. The process according to claim 1, wherein R7 and R8 are unsubstituted or substituted alkyl or alkoxyalkyl with 1 to 20 C atoms or cycloalkyl with 3 to 10 ring carbon atoms, or R7 and R8 together are -(CH2)-n, where n = 2 to 8.

3. The process according to claim 1, wherein the substitu-ents for R7 and R8 are chosen from alkyl, cycloalkyl and alkoxy.

4. The process according to claim 1, wherein a salt or a complex compound of ruthenium is used as the catalyst.

5. The process according to claim 1, wherein 0.001-20 mol%, based on the azobenzene of the formula II, of the ruthenium catalyst is used.

6. The process according to claim 1, wherein the reaction is carried out in 3 polar aprotic solvent.

7. The process according to claim 6, wherein the solvent is an N-alkylated acid amide, in particular tetramethylurea.

8. The process according to claim 1, carried out at a tem-perature of 120 to 250°C.

9. The process according to claim 1, wherein the molar ratio of secondary alcohol to azobenzene is at least 1 : 1.

10. The process according to claim 1, wherein the basic compound is a tertiary amine or an alkali metal or alkaline earth metal salt of a carboxylic acid.

11. The process according to claim 10, wherein at least 011 mol%, based on the azobenzene of the formula II, of the basic compound is used.

12. The process according to claim 9, wherein the molar ratio of secondary alcohols to azobenzene is 1.0 : 1 to 2.5 : 1, and up to stoichiometric amounts, based on the azo-benzene, of the basic compound are used.

13. The process according to claim 9, wherein the molar ratio of secondary alcohol to azobenzene is 3 : 1 to 8 : 1 and 0.1 to 20 mol% of the basic compound is used.