GB2195118A - Manufacture of di-alkoxy-substituted 2-dialkylaminobenzenediazonium salts - Google Patents

Abstract

Dialkoxy-substituted 2-dialkylaminobenzenediazonium salts that can be used for the manufacture of azo dyestuffs and as light-sensitive components in photographic and reprographic systems are obtained by a process in which 2,3-dinitrohydroquinone dialkyl ethers are mono-aminated with secondary amines and, optionally after halogenation, the result 2-dialkylamino-3,6-dialkoxynitrobenzenes are reduced to the corresponding amines and these are then diazotised to produce 2-dialkylamino-3,6-dialkoxybenzenediazonium salts or 2-dialkylamino-5-halo-3,6-dialkylaminobenzenediazonium salts. <IMAGE>

Description

SPECIFICATION Process for the manufacture of alkoxy-substituted 2-dialkylaminobenzediazonium salts The invention relates to a process for the manufacture of substituted 2-dialkylaminobenzenediazonium salts that can be used, for example, for the manufacture of azo dyestuffs and as lightsensitive components in photographic and reprographic systems.

2-Dialkylaminobenzenediazonium salts are manufactured by nitrating chloro- or bromo-benzene and, after separating the isomeric nitrohalobenzenes, reacting 2-nitrohalobenzene with a secondary amine to form 2-dialkylaminonitrobenzene which is reduced to 2-dialkylaminoaniline and is then diazotised to form the 2-dialkylaminobenzenediazonium ion (J. prakt. Chem. 315, 725, 1973).

A 2-morpholino-5-methoxybenzenediazonium salt is also known (DE-PS 1 204 069). It is manufactured by nitrating tacetoanisidide to form 3-nitro-4-acetamidoanisole which is hydrolysed to form 3-nitro-4-aminoanisole. This product is reacted by the Sandmeyer reaction to form 3-nitro-4-chloroanisole and, by boiling with excess morpholine, 3-nitro-4-morpholinoanisole is obtained therefrom. By reduction of the nitro compound to form 2-morpholino-5-methoxyaniline and subsequent diazotisation, the 2-morpholino-5-methoxybenzenediazoium salt is obtained.

It is also known that an analogous nitration of 2,5-dialkoxychlorobenzenes results exclusively in 2,5-dialkoxy-4-nitrochlorobenzenes (Rec. trav. chim. 72, 91, 1953) and that nitration of 2,5dialkoxyacetoanilides results in 2,5-dialkoxy-4-nitroacetoanilides (Rec. trav. chim. 72, 178, 1953).

2,5-Dialkoxy-6-nitrohalobenzenes and 2,5-dialkoxy-6-nitroacetoanilides and, therefore, 2-dialkylamino-3,6-dialkoxybenzenediazonium salts cannot be manufactured by this generally known process.

The synthesis of 2-dialkylamino-5-halobenzenediazonium salts is known (DD-WP 159 730). By nitrating p#dichloro- or p#dibromo-benzene, 2,5-dichloro- or 2,5-dibromo-nitrobenzenes, respectively, are obtained which, by nucleophilic substitution of the o-chlorine and o-bromine, can be converted into 2-dialkylamino-5-chloro- and 2-dialkylamino-5-bromo-nitrobenzenes respectively.

The diazonium salts are then obtained by reduction of the nitro group and subsequent diazotisation of the resulting amine.

It is also known that an analogous nitration of 2,5-dihalohydroquinone dialkyl ethers does not take place under mild conditions and, under drastic conditions, in the case of the 2-5-diiodohydroquinone dialkyl ethers, always results in a replacement of the two halogen atoms by nitro groups (J. Chem. Soc. 109, 1087, 1916) and, in the case of the 2,5-dibromo- and 2,5-dichloroderivatives, results in the alkoxy groups being split off to produce 2,5-dibromo- and 2,5dichlorobenzoquinones (Mh. Chem. 45, 71, 1924). 2,5-Dialkoxy-3,6-dihalonitrobenzenes and, therefore, 2-dialkylamino-3-alkoxy-5-halo-6-alkoxybenzenediazonium salts cannot be manufactured by this generally known process.

The invention makes it possible to manufacture substituted 2-dialkylaminobenzenediazonium salts having alkoxy groups from simple starting materials.

The present invention provides a process for the manufacture of an alkoxy-substituted 2dialkylaminobenzenediazonium salt which comprises reacting a 2,3-dinitrohydroquinone dialkyl ether of the general formula I

wherein Rt represents an alkoxy group having from 1 to 6 carbon atoms and the two R' groups may be the same or different, with a secondary amine of the general formula ll

wherein R2, R3 are the same or different and each represents an alkyl group having from 1 to 6 carbon atoms, an aralkyl group having from 1 to 4 carbon atoms in the alkyl moiety, a hydroxyalkyl group having from 1 to 6 carbon atoms, a chloroalkyl group having from 1 to 6 carbon atoms, or R2 and R3 together represent an alkylene group needed to complete a 5- or 6-membered heterocyclic ring which may contain at least one further hetero atom, for example, an oxygen, sulphur or nitrogen atom, and X9 represents an anion, reducing the resulting 2-dialkylamino-3 ,6-dialkoxynitrobenzene of the general formula Ill

wherein R', R2, R3 have the meanings given above, to the corresponding amine of the general formula IV

wherein R', R2, R3 and XE have the meanings given above, and then diazotising to a 2-dialkylamino3,6-dialkoxybenzenediazonium salt of the general formula V

wherein R1, R2, R3 and X have the meanings given above and the anion represented by XS may be the same as or different from the anion represented by XE in formula ll and/or formula IV, or halogenating a 2-dialkylamino-3,6-dialkoxy-nitrobenzene of the general formula Ill, reducing the resulting 2-dialkylamino-5-halo-3,6-dialkoxynitrobenzene of the general formula Vl

wherein R', R2, R3 have the meanings given above and R4 represents chlorine or bromine, to the corresponding amine of the general formula VII

wherein R1, R2, R3, R4 and XE have the meanings given above, and then diazotising to a 2-dialkylamino-5-halo-3,6-dialkoxybenzenediazonium salt of the general formula VIII

wherein R', R2, R3, R4 and XE have the meanings given above, and the anion represented by XE may be the same as or different from the anion represented by Xe in formula II and/or formula VII.

The 2,3-dinitrohydroquinone dialkyl ethers may be obtained in any suitable manner, for example, by dinitration of hydroquinone dialkyl ethers. The amination of the 2,3-dinitrohydroquinone dialkyl ethers may be carried out under, for example, the conditions customary for amination.

As secondary amines there are used especially morpholine, dimethylamine, pyrrolidine and piperidine. The 2-dialkylamino-3,6-dialkoxynitrobenzenes obtained are then reduced to the corresponding amines by any suitable method, for example, by catalytic hydrogenation or by means of zinc power and hydrochloric acid, and diazotised in any suitable manner, for example, using sodium nitrite or halogenated using bromine, chlorine gas, sulphuryl chloride or any other suitable brominating or chlorinating agent. The subsequent reduction to the corresponding amines may be effected, for example, by catalytic hydrogenation or reduction by means of zinc dust and hydrochloric acid. The amines are then diazotised in any suitable manner, for example, using sodium nitrite.

The diazonium compounds may be isolated in any suitable form, for example, in the form of zinc chloride double salts, tetrafluoroborates or, together with other suitable anions, in the form of diazonium salts, or may be reacted with azo couplers to form azo dyestuffs. The diazonium salts may be used as light-sensitive components in photographic and reprographic systems.

The following Examples illustrate the invention.

Example I a) 2,3-dinitrohydroquinone diemthyl ether 55.2 g (0.4 mol) of hydroquinone dimethyl ether are dissolved in 140 ml of glacial acetic acid.

140 ml of concentrated nitric acid (D=1.4) are added dropwise while stirring at 25-30 C.

Stirring is continued for one hour and 500 ml of cold water are added. The product is filtered off with suction, washed with water and dried. The product is separated from the 2,5-dinitrophydroquinone dimethyl ether, which has been produced therewith, by fractional crystallisation from ethyl acetate.

Yield: 60.5 g (66% of the theoretical yield).

M.p. 185-186"C.

b) 2-dimethylamino-3,6-dimethoxynitrobenzene 45.6 g (0.2 mol) of 2,3-dinitrohydroquinone dimethyl ether are dissolved in 200 ml of pyridine.

359 of NaHCO3 and a solution of 33 g of dimethylamine hydrochloride in 25 ml of warm water are added to the solution and the whole is then boiled under reflux for 6 hours.

After cooling, the reaction solution is stirred with 800 ml of water, and the product is filtered off with suction, washed with water and dried.

Recrystallisation from alcohol yields light-yellow crystals.

Yield: 32.7 g (72% of the theoretical yield).

M.p. 76-77 C.

c) 2-dimethylamino-3,6-dimethoxybenzenediazonium tetrafluoroborate 19.6 g (0.1 mol) of 2-dimethylamino-3,6-dimethoxyaniline, obtained by catalytic hydrogenation of 2-dimethylamino -3,6-dimethoxynitrobenzene, are dissolved in 50 ml of concentrated hydrochloric acid and 30 ml of water. While stirring and cooling, a solution of 7 g of NaNO2 in 30 ml of water is added dropwise at 0 C. Stirring is continued for 10 minutes and then a solution of 20 g of NaBF4 in 50 ml of water is added dropwise. While further cooling, the whole is stirred for 2 hours, and the product is subsequently filtered off with suction, washed with cold water and dried. Dark-red crystals are obtained.

Yield: 19.2 g (61% of the theoretical yield).

M.p. 128-130 0C (decomposition).

d) 1 -phenyl-3-methyl-4-(2'-dimethylamino-3',6'-dimethoxy-phenylazo)-pyrazol-5-one.

Instead of being added to an aqueous NaBF4 solution, the diazonium solution obtained under 1 c) is added dropwise, while stirring, to a solution of 17.4 g (0.1 mol) of 1-phenyl-3-methylpyra- zol-5-one in 100ml of methanol and 50 ml of water to which 30 g of sodium acetate, 5 g of NaOH and 200 g of ice have been added. The whole is then stirred for 2 hours, washed with water and dried. A yellow azo dyestuff is obtained in quantitative yield.

e) 2-dimethylamino-3-methoxy-5-bromo-6-methoxynitrobenzene 0.1 mol (22.6 g) of the 2-dimethylamino-3,6-dimethoxynitrobenzene manufactured as described under 1b) are dissolved in# 250 ml of glacial acetic acid. While stirring, a solution of 10 ml of bromine in 60ml of glacial acetic acid is added dropwise at 20-25 C. The whole is subsequently stirred for 2 hours and then 200 ml of water are added. The product which precipitates is filtered off with suction and dried.

Yield: 30 g (98% of the theoretical yield).

M.p. 98-99 C.

After recrystallisation from ethanol, analytically pure 2-dimethylamino-3-methoxy-5-bromo-6methoxynitrobenzene (m.p. 101 C) is obtained.

f) 2-dimethylamino-3-methoxy-5-bromo-6-methoxybenzenediazonium tetrachlorozincate 0.05 mol (15.3 g) of 2-dimethylamino-3-methoxy-5-bromo-6-methoxynitrobenzene is suspended in 50 ml of concentrated hydrochloric acid and 40 ml of water. At 200C (ice-bath), 13 g of zinc dust are added in portions while stirring. When the reaction solution is colourless, it is filtered and 10 ml of concentrated hydrochloric acid are added to the filtrate and, while stirring at 0-2 C, a solution of 3.5 g of sodium nitrite in 10 ml of water is added dropwise thereto. 30 ml of cold-saturated sodium chloride solution are then added and, while further cooling, the whole is then stirred for one hour.The reaction mixture is kept overnight in a refrigerator, and the product is then filtered off with suction and washed with cold water.

Yield: 9.6 g (63% of the theoretical yield).

M.p. 132-134"C (decomposition).

g) 1 -(2'-dimethylamino-3'-methoxy-5'-bromo-6'-methoxyphenylazo)-2-naphthol.

Soda is added to the diazonium salt solution obtained as described under 1f) until all the zinc has precipitated in the form of zinc carbonate. The mixture is then filtered and the filtrate is added dropwise, while stirring and cooling, to a solution of 7.2 g (0.50 mol) of 2-naphthol in 70 ml of 10% aqueous NaOH. The whole is then stirred for 2 hours, and the product is filtered off with suction, washed with water and dried. A red azo dyestuff is obtained in quantitative yield.

Example 2 a) 2-nitrophydroquinone diethyl ether 66.4 g (0.4 mol) of hydroquinone diethyl ether are dissolved in 500 ml of glacial acetic acid.

While stirring at 20-25 C, 120 ml of dilute nitric acid (D=1.24) are added dropwise. The whole is then stirred for one hour and 2 litres of cold water are added. The product is filtered off with suction, washed with water and dried.

Yield: 82 g (97% of the theoretical yield).

M.p. 45-47 C.

Recrystallisation from aqueous ethanol (1:1 v/v) yields analytically pure 2-nitrohydroquinone diethyl ether (m.p. 47-48 C).

b) 2,3-dinitrohydroquinone diethyl ether 84.4 g (0.4 mol) of 2-nitrohydroquinone diethyl ether are dissolved in 450 ml of glacial acetic acid. While stirring at 20-25 C, a mixture of 40 ml of concentrated nitric acid (D= 1.4) and 50 ml of concentrated sulphuric acid are added dropwise. The whole is then stirred for 30 minutes and subsequently heated to 550C on a water bath. The reaction mixture is maintained at that temperature for 15 minutes and is then cooled to room temperature, and the product is filtered off with suction, washed with water and dried.

Yield: 89 g.

M.p. 128-133"C.

Fractional crystallisation from ethanol separates the product from the 2,5-dinitrohydroquinone diethyl ether which has been produced therewith.

Yield: 53 g (52% of the theoretical yield).

M.p. 132-133"C.

c) 2-morpholino-3,6-diethoxynitrobenzene 51.2 g (0.2 mol) of 2,3-dinitrohydroquinone diethyl ether are boiled under reflux for 6 hours with 70 g of morpholine. After cooling, the reaction solution is stirred with 400 ml of water, and the product which precipitates is filtered off with suction and washed with water.

Yield: 59 g (100% of the theoretical yield).

M.p. 91-94 C.

Recrystallisation from ethanol yields analytically pure 2-morpholino-3,6-diethoxynitrobenzene (m.p. 93-95"C).

d) 2-morpholino-3 ,6-diethoxynitrobenzenediazonium tetrafluoroborate 2-Morpholino-3,6-diethoxyaniline obtained by catalytic reduction of 2-morpholino-3,6-diethoxynitrobenzene is diazotised analogously to Example 1c) and isolated in the form of the tetrafluoroborate.

In a 0.1 mol batch, 29.2 g (80% of the theoretical yield) of 2-morpholino-3,6-diethxynitrobenzenediazonium tetrafluoroborate are obtained.

e) 2'-morpholino-3',6'-diethoxy-2,4-dihydroxyazobenzene The diazonium salt solution manufactured under 2d) is added dropwise, while stirring and cooling, to a solution of 11 g (0.1 mol) of resorcinol in 120ml of 10% aqueous NaOH. An orange dyestuff is obtained in quantitative yield.

f) 2-morpholino-3-ethoxy-5-chloro-6-ethoxynitrobenzene 0.1mol (29.6 g) of 2-morpholino-3,6-diethoxynitrobenzene is dissolved in 240 ml of glacial acetic acid. While stirring, dry chlorine gas is passed into the reaction solution for 4 hours at 20-25 C. The reaction solution is subsequently stirred for 2 hours and, while stirring, 300 ml of water and then 300 ml of 20% NaOH are added. The product which precipitates is filtered off with suction and washed with water.

Yield: 31.8 g (96% of the theoretical yield).

M.p. 92-95 C.

Recrystallisation from ethanol yields analytically pure 2-morpholino-3-ethoxy-5-chloro-6-ethoxynitrobenzene (m.p. 97-98 C).

g) 2-morpholino-3-ethoxy-5-chloro-6-ethoxynitrobenzene is catalytically hydrogenated and the amine is diazotised at 0 C analogously to Example inc). The diazonium salt is precipitated by adding cold-saturated aqueous sodium tetrafluoroborate solution.

Yield: 72% of the theoretical yield.

M.p. 1 19-1220C (decomposition).

h) 1-(2'-morpholino-3'-ethoxy-5'-chloro-6'-ethoxyphenylazo)-2,3-dihydroxynaphthalene 16 g (0.1 mol) of 2,3-dihydroxynaphthalene are dissolved in 100 ml of 10% NaOH. Then, while stirring vigorously, acetic acid is added to the solution until a weakly acid reaction is obtained. There is then added to the resulting suspension, while stirring and cooling, the diazonium salt solution manufactured under lug). Aqueous sodium acetate solution is then added until an alkaline reaction is obtained. The reaction mixture is kept slightly alkaline over the course of 2 hours by the further addition, in portions, of aqueous sodium acetate solution. The product is then filtered off with suction, washed with water and dried. A red azo dyestuff is obtained in quantitative yield.

Example 3 2,3-Dinitrohydroquinone diethyl ether is reacted with 70 g of piperidine analogously to Example 2. 57.6 g (98% of the theoretical yield) of crude product having a melting point of 91-94"C is obtained. Recrystallisation from aqueous ethanol yields analytically pure 2-piperidino-3,6-diethoxynitrobenzene (m.p. 94-96 C).

0.1 mol (29.4 g) of 2-piperidino-3,6-diethoxynitrobenzene are dissolved in 240 ml of glacial acetic acid. 16.4 ml of sulphuryl chloride in 40 ml of glacial acetic acid are added dropwise thereto while stirring at 20-25 C. Stirring is continued for 4 hours and then 300 ml of water are added. Subsequently, 300 ml of 20% NaOH are added. The product which precipitates is filtered off with suction and washed with water.

Yield: 29.6 g (90% of the theoretical yield).

M.p. 67-70 C.

Recrystallisation from ethanol yields analytically pure 2#piperidino-3-ethoxy-5-chloro-6-ethoxyni- trobenzene (m.p. 71-73 C).

The piperidino-3-ethoxy-5-chloro-6-ethoxynitrobenzene is catalytically hydrogenated and the amine is diazotised in aqueous hydrochloric acid at 0 C. The diazonium salt is precipitated by adding cold-saturated aqueous sodium tetrafluoroborate solution (yield: 77% of the theoretical yield. M.p. 104--106"C (decomposition)) or, by adding the diazonium salt solution to a solution of 15 g of N,n-diethylaniline in 60 ml of glacial acetic acid and 700 ml of ice-water containing 70 g of sodium acetate, a brown dyestuff is obtained in 80% yield.

Example 4 Hydroquinone dibutyl ether is dinitrated analogously to Example 1. Of the resulting mixture, approximately one quarter consists of 2,5-dinitrohydroquinone dibutyl ether and three quarters of 2,3-dinitrohydroquinone dibutyl ether. The crude product is reacted with morpholine analogously to Example 2 to produce 2,5-dibutoxy-4-morpholinonitrobenzene and 2-morpholino-3,6-dibutoxynitrobenzene. This mixture is catalytically reduced in three times the amount of absolute alcohol using Raney nickel as the catalyst. The catalyst is then filtered off and there are added to the hot solution, per 0.1 mol of starting material, 15 ml of concentrated HCI.

The mixture is boiled up once more and then cooled, and the resulting precipitate is filtered off with suction.

There are thus obtained, in a 0.4 mol batch, 77 g (62% of the theoretical yield) of 2morpholino-3,6-dibutoxyaniline hydrochloride (m.p. 145-146.5"C). The 2,5-dibutoxy-4-morpholinoaniline dihydrochloride which is also produced remains in solution.

Analogously to Example 1, the 2-morpholino-3,6-dibutoxyaniline hydrochloride can be diazotised and the diazonium salt precipitated in solid form or reacted with the couplers from Examples 1-3 to form azo dyestuffs.

Example 5 Hydroquinone dibutyl ether is dinitrated analogously to Example 1. The resulting mixture of 2,5-dinitrohydroquinone dibutyl ether and 2,3-dinitrohydroquinone dibutyl ether is separated by fractional crystallisation from isopropanol.

Analogously to Example 2, 2,3-dinitrohydroquinone dibutyl ether (m.p. 72-74 C) is reacted with piperidine to form 2-piperidino-3,6-dibutoxynitrobenzene which is then recrystallised from ethanol (m.p. 70-72 C).

Analogously to Example 1, this product is reacted with bromine to form 2-piperidino-3butoxy-5-bromo-6-butoxynitrobenzene which is catalytically reduced with Raney nickel and diazotised analogously to Example 1. A diazonium salt solution containing 0.1 mol of 2-piperidino-3 butoxy-5-bromo-6-butoxybenzenediazonium salt is added dropwise at OOC, while stirring well, to a solution of 26.3 g (0.1 mol) of 2-hydroxy-3-naphthanilide in 120 mol of 10% naOH and 60 ml of methanol. Stirring is continued for 2 hours and the product is filtered off with suction, washed with water and dried. A red dyestuff is obtained in quantitative yield.

Example 6 Analogously to Example 2, 2,3-dinitrohydroquinone diethyl ether is reacted with pyrrolidine to form 2-pyrrolidino-3,6-diethoxynitrobenzene which is catalytically reduced with Raney nickel and diazotised analogously to Example 1. The resulting diazonium solution is coupled analogously to Example 5 with 2-hydroxy-6-methoxy-3-naphth-o'-toluidide to produce a blue azo dyestuff.

Claims (10)

1. A process for the manufacture of an alkoxy-substituted 2-dialkylaminobenzenediazonium salt which comprises reacting a 2,3-dinitrohydroquinone dialkyl ether of the general formula I

wherein R' represents an alkoxy group having from 1 to 6 carbon atoms and the two R' groups may be the same or different, with a secondary amine of the general formula II

wherein R2, R3 are the same or different and each represents an alkyl group having from 1 to 6 carbon atoms, an aralkyl group having from 1 to 4 carbon atoms in the alkyl moiety, a hydroxyalkyl group having from 1 to 6 carbon atoms, a chioroalkyl group having from 1 to 6 carbon atoms, or R2 and R3 together represent an alkylene group needed to complete a 5- or 6-membered heterocyclic ring which may contain at least one further hetero atom, and xe represents an anion, reducing the resulting 2-dialkylamino-3,6-dialkoxynitrobenzene of the general formula Ill

wherein R1, R2, R3 have the meanings given above, to the corresponding amine of the general formula IV

wherein R', R2, R3 and XE have the meanings given above, and then diazotising to a 2-dialkylamino3,6-dialkoxybenzenediazonium salt of the general formula V

wherein R', R2, R3 and XE have the meanings given above and the anion represented by XS may be the same as or different from the anion represented by XE in formula II and/or formula IV, or halogenating a 2-dialkylamino-3,6-dialkoxynitrobenzene of the general formula Ill, reducing the resulting 2-dialkylarnino-5-halo-3,6-dialkoxynitrnbenzene of the general formula Vl

wherein R', R2, R3 have the meanings given above and R4 represents chlorine or bromine, to the corresponding amine of the general formula Vll

wherein R', R2, R3, R4, and XE have the meanings given above, and then diazotising to a 2-dialkylamino-5-halo-3,6-dialkoxybenzenediazonium salt of the general formula VIII

wherein R', R2, R3, R4 and X9 have the meanings given above and the anion represented by XE may be the same as or different from the anion represented by XS in formula II and/or formula VII.

2. A process as claimed in claim 1, wherein the secondary amine of the general formula 11 is morpholine, dimethylamine, pyrrolidine or piperidine.

3. A process as claimed in claim 1, or claim 2, wherein a diazonium compound is isolated in the form of a zinc chloride double salt or a tetrafluoroborate.

4. A process as claimed in claim 1, wherein any individual step is carried out substantially as described in any one of the Examples herein.

5. A process as claimed in claim 1 carried out substantially as described in any one of the Examples herein.

6. A 2-dialkylamino-3,6-dialkoxybenzenediazonium salt whenever prepared by a process as claimed in any one of claims 1 to 5.

7. A coupling process wherein a diazonium salt as claimed in claim 6 is reacted with an azo coupler to form an azo dyestuff.

8. A dyestuff prepared by a process as claimed in claim 7.

9. A photographic or reprographic material comprising a diazonium salt as claimed in claim 6.

10. Any novel feature described herein or any novel combination of hereindescribed features.