GB1598799A

GB1598799A - Process for the manufacture of azo dyes

Info

Publication number: GB1598799A
Application number: GB5133477A
Authority: GB
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1978-05-25
Filing date: 1978-05-25
Publication date: 1981-09-23

Description

(54) PROCESS FOR THE MANUFACTURE OF AZO DYES (71) We, IMPERIAL CHEMICAL INDUSTRIES LIMITED, Imperial Chemical House, Millbank, London SW1P 3JF, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to an improved process for the manufacture of azo dyes containing cyano groups.

In our co-pending UK Patent Application No. 22283/76 (UK Patent Specification No. 1,578,732) there is described and claimed a process for the manufacture of azo dyes of the formula: D-A-N=N-B wherein A is an aromatic radical, B is an optionally substituted benzenoid ring carrying a substituted nitrogen atom in the para position to the azo link and D is a cyano radical ortho to the azo group, which comprises reacting an azo dye of the same formula except that D is an iodine, bromine or chlorine atom in the presence of a phase transfer catalyst with an alkali metal or alkaline earth metal cyanide in the presence of a catalytic amount of a copper compound.

A refinement of this process which is also described in UK Patent Application No. 22283/76 (UK Patent Specification No. 1,578,732) is the gradual addition of the metal cyanide, preferably in aqueous solution, as the reaction proceeds. This is thought to minimise degradation of the azo dyestuff by high concentrations of the metal cyanide. However, minor amounts of coloured by-products are still encountered, especially when dyes of blue and greenish blue shade are being prepared. These by-products have the same formula as the dyestuff D-A-N=N-B except that D is either a hydrogen atom or a second dyestuff group of the formula -A-N=N-B. The present invention tends to reduce or even eliminate the formation of these by-products.

According to the present invention we provide a process for the manufacture of azo dyes of the formula: D-A-N=N-B wherein A is an aromatic radical, B is an N-substituted p-aminophenyl radical and D, which is ortho to the azo group, is a cyano radical, which comprises reacting in a liquid medium in the presence of a phase transfer catalyst an azo dye of the same formula except that D is an iodine, bromine, or chlorine atom with a pre-formed mixture of a copper compound and an alkali metal cyanide or alkaline earth metal cyanide, there being insufficient of the copper compound present to complex with all of the metal cyanide.

While the invention may be used to advantage when the process is carried out in an organic solvent, it is of particular value for the manufacture of azo dyes in aqueous medium especially where the dyes are free of water-solubling groups. In this latter case the reaction proceeds with the dyes held in aqueous suspension. The reaction normally proceeds at the boil and sometimes at lower temperatures thereby obviating the use of the pressure equipment hitherto employed.

By the expression "phase transfer catalyst" we mean a substance which being at least partly present in or "wetted" by a first (usually organic) phase, promotes reaction by transferring a reactant from a second (usually aqueous) phase to the first phase where it undergoes reaction thereby releasing the phase transfer catalyst for re-use in transferring further reactant.

Phase transfer catalysts are reviewed by E. V. Dehmlow in Angewandte Chemie (International Edition) Vol 13, No. 3, 1974, page 170.

Other reviews are by Josef Dockx in Synthesis 1973 at pages 441456, and by C. M. Starks in the Journal of the American Chemical Society 93:1 Jan 13, 1971 at pages 195-199.

Suitably the phase transfer catalyst is a quaternary ammonium salt which may be of the general formula:

wherein R, R', R" and R"', which may be the same or different are alkyl, hydroxylalkyl, aryl, aralky, for example benzyl, or cycloalkenyl groups, or alternatively two of these may together form a ring system containing 5-7 carbon atoms. The positively charged nitrogen atom may be part of an aromatic system, as for example, in cetyl pyridinium bromide. X- is an anion. Conveniently it is a halogen, a bisulphate or a half-sulphate or a third phosphate ion. Further, double or multifunctional quaternary salts in which the formula (RR'R"R"'N)+X- is repeated a plurality of times may also be used. In such salts the nitrogen atoms are linked by an aralkyl group or long chain alkyl groups containing upwards of 10 carbon atoms.

Essentially a phase transfer catalyst of this type is a cationic species which contains bulky organic groups to make it soluble in organic media, and which when dissolved in an organic medium increases by virtue of its positive charge the solubility in the organic medium of anionic species required for reaction therein.

The molecular geometry of the quaternary ammonium moiety is not of prime importance, but to confer preferential solubility in the organic phase rather than the aqueous phase it is preferred that the total number of carbon atoms per positively charged atom in the molecule should be greater than 10, and there is little advantage in the number being above 70. It is especially preferred that the number should lie between 16 and 40. The nature of the anion, provided it is inert, is not important.

Although, surprisingly, the phase transfer catalyst accelerates the reaction of the invention when carried out in organic solvents, it is particularly efficacious when the reaction medium is largely aqueous.

The quaternary ammonium salt may be prepared in situ, for example by including in the reaction mixture a tertiary amine, such as pyridine or triethylamine, together with an alkylating agent such as benzyl chloride or diethyl sulphate.

As examples of quaternary ammonium salts we would mention cetyl trimethyl ammonium bromide, dicetyldimethyl ammonium chloride, octyl tributyl ammonium bromide, tetrabutyl ammonium bromide, trioctyl methyl ammonium chloride, benzyl dimethyl lauryl ammonium chloride, benzyl tri-n-butylammonium chloride, dilauryl dimethyl ammonium chloride tetrabutyl ammonium sulphate and dieicosyl dimethyl ammonium chloride.

Quaternary phosphonium salts of similar formula to the above quaternary ammonium salts, with the N atom replaced by P, may also be used. An example is cetyl tripropyl phosphonium bromide. We also mention sulphonium, pyrylium, arsonium and iodonium salts which bear sufficiently large organic residues to make them at least partly soluble in organic solvents.

Also effective as phase transfer-catalysts for the practice of this invention are cation complexing agents such as crown ethers (macrocyclic polyethers) of the type described by C. J. Pedersen in the Journal of the American Chemical Society: 89 7017 (1967). While, in the absence of added complex forming salts, these compounds show no activity where cuprous cyanide itself is the reagent we have found that they are well adapted to catalysing reaction with metal cyanocuprates particularly alkali metal cyanocuprates.

When a crown ether is used as catalyst the number of atoms in its ring should be appropriate to the size of the metal cation of the cyanocuprate, following principles now well documented. Thus, for example, 18-crown-6 and its substituted derivatives are preferred for catalysing reactions of the potassium cyanocuprates whereas either 15-crown-5 or 18-crown-6 and their substituted derivatives may be used with sodium cyanocuprates.

While the unsubstituted crown ethers are very suitable for catalysing the reaction when it is carried out in organic solvents with little or no water present, it is preferred that in predominantly aqueous media the crown ether should bear one or more hydrophobic substituents. The nature of these substituents, each of which may be attached to more than one atom of the crown ring, is otherwise not critical provided that the substituent is not so bulky, or does not bridge the crown ether in such a way, as to destroy its complex forming properties.Examples of suitable crown ethers are: 12-crown-4, 2,4,6,8-tetramethyl- 12-crown-4, 15-crown-5, benzo- 15-crown-5, perhydrobenzo- 1 5-crown-5, 1 8-crown-6, dibenzo- 18-crown- 6,tris(tetrahydrofuranyl- 18-crown-6 (I), perhydrodibenzo- 1 8-crown-6 (II, R=H), and its di-terbutyl derivative (II, R=ter-butyl), and dicyclohexyl-24-crown-8.

Also useful as catalysts are certain non-cyclic polyethers, known as "polypode ligands", which complex cations in a manner very similar to that of crown ethers.

Examples are benzene hexakis (2-thin-5,8,1 1-trioxapentadecane) described by F.

Vogtle and E. Weber: Angewandte Chemie International Edition, 1974 13 p. 814, and the triazine and pentaerithritol derivatives (III and IV) described by F.

Montanari and others: Tetrahedron Letters pages 1381-1384, 1976. Some activity is shown by even simpler polyethers with suitable end groups (F. Vogtle and H.

Sieger, Angewandte Chemie International Edition 1977 16 pages 396-398)

R=[n-C8H17(OCH2CH2)4j2N- Ill

We also mention as useful cation complexing agents, closely related to crown ethers, other macrocyclic, macrobicyclic or macropolycyclic heterocycles, for example those known as cryptates or cryptands, in which the stability of the complex may be enhanced by entrapment of the cation within a threedimensional cage structure. Examples are V and VI, and others are described by G. W. Gokel and H. D. Durst: Synthesis, 1976 pages 168-184.

When the process of the invention is carried out in aqueous medium it may be advantageous to add a water-immiscible solvent, for example, toluene, xylene, chlorobenzene, 1 ,2-dichloroethane, 1,1,1 -trichloroethane, 1 ,2-dibromoethane, onitrotoluene, octanol, benzyl, alcohol, methyl isobutyl ketone ethyl acetate, butylacetate, ethyl benzoate, cyclohexanol or cyclohexanone. Particularly useful are anisole, acetophenone and nitrobenzene. The solvent need not be present in amount sufficient to dissolve completely the dye but only in catalytic quantity which serves to 'soften' or lower the melting point of the dye. After reaction the solvent may be separated from the aqueous suspension by, for example, steam distillation and allowed to separate from the distillate for re-use.The inclusion of a water-immiscible solvent often further increases the rate of reaction.

The mixture of the copper compound and alkali metal or alkaline earth metal cyanide is prepared prior to reaction with the halogen containing dyestuff conveniently by dissolving the copper compound in a solution of the cyanide, the mixture normally being added to the dye while the latter is being stirred in a liquid medium.

It is believed that cyanocuprate complexes are formed when the copper compound is dissolved in the alkali metal or alkaline earth metal cyanide solution according (when the metal is monovalent) to the following equations: Cu X+2 MCN~MCu (CN)2+MX Cu X+3 MCNM2Cu (CN)3+MX Cu X+4 MCN < M3Cu (CN)4+MX When an alkaline earth metal is used, complexes of the formulae M [Cu(CN)2]2, MCu(CN)3 and M3[Cu(CN)4]2 are obtained.

The copper compound used is preferably a cuprous compound, conveniently cuprous chloride, cuprous bromide or cuprous cyanide, but other copper compounds may be suitable.

Sodium and potassium cyanides are the favoured metal cyanides for use in the invention with a preference for the sodium salt on economy grounds.

Since insufficient of the copper compound is used to complex with all of the metal cyanide, it will be appreciated that the mixture will contain free cyanide ions and that the tetracyano cuprate complex will predominate.

We have found that as little as 0.005 moles of copper/mole of replaceable halogen can be used with a quantity of alkali metal cyanide such as to provide sufficient cyano radicals to react with all of the halogeno dyestuff. Conveniently 0.1 mole of the copper compound is dissolved in 0.90 mole of metal cyanide, but good results are obtained when 0.01 mole of the copper compound is dissolved in 0.99 mole of the metal cyanide.

This is most surprising because according to UK Patent Specification 1438374, which comprehensively described cyano cuprate complexes, it is preferred to use the complex MCu(CN)2 in the preparation of cyano group-containing azo dyestuff because it is said to be the more stable and reactive of the complexes. It is also said that it is important that essentially no free cyanide ions are present during the performance of the process because this leads to degradation of the dyestuff. Since the formation of the complex M3Cu(CN)4 requires a greater usage of alkali metal cyanide which is more likely to lead to an excess of cyanide ions being present this is a further reason why the complex M3Cu(CN)4 is not favoured.

Further, it is well understood in the field of phase transfer catalysis, that it is very difficult to transfer anions bearing a double negative charge. Thus most discussions of phase transfer catalysts deal exclusively with singly charged anions (e.g. Dehmlow, loc. cit). In a later review, (Angewandte Chemie. International Edition 16 1977 at page 498), Dehmlow states that unlike hydrogen sulphate (HSO4), sulphate (SO4=) remains quantitatively in the aqueous phase, and that thrice charged anions are even less transferable than doubly charged anions.

Accordingly it is quite unexpected that a phase transfer catalyst should be effective under the conditions of the present invention where the thrice charged tetracyanocuprate predominates.

These conditions are however most advantageous since, without using the reactive but expensive iodine containing dyes as starting materials, they allow preparation of cyano dyestuffs, particularly blue and greenish blue dyes, free from the large amounts of copper which are difficult to remove and which are environmentally unacceptable, both in the product and in the process effluent.

The aromatic radical A may be any such radical including heteroaromatic radicals. Of particular interest are azo dyes where A is a substituted phenyl radical, but the process of the invention is also useful where A is, for example, a benzoisothiazolyl-l,2 or -2,1-radical, a naphthyl or quinolyl radical.

Dyes which can conveniently be prepared by the process of the invention have one of the following general formulae:

wherein T is hydrogen, lower alkyl, lower alkoxy, cyano, halogen, nitro, lower alkylsulphonyl, lower alkylsulphonamido or a radical of the formula:

E is hydrogen, lower alkyl, lower alkoxy, lower alkyl carbonyl, lower alkoxy carbonyl, trifluoromethyl, acylamino, halogen, optionally substituted phenylazo, cyano or especially nitro; O is hydrogen or nitro; J is hydrogen or nitro; Y is hydrogen, lower alkyl, lower alkoxy or halogen; Z is hydrogen, lower alkyl, lower alkoxy, halogen, and particularly acylamino especially acetylamino and propionylamino; K is hydrogen; or Z and K together with the carbon atoms to which they are attached form a benzene ring which bears a sulphonic acid group or alkali metal salt thereof; R, is lower alkyl, hydroxy lower alkyl loweralkoxy lower alkyl, lower alkoxy carbonyl lower alkyl cyano lower alkyl, and phenyl lower alkyl, cyclohexyl or phenyl; R2 is hydrogen, lower alkyl hydroxy lower alkyl, lower alkoxy lower alkyl, lower alkoxy carbonyl lower alkyl or lower alkyl carrying a pyridinium salt; and, in particular, either of both R, and R2 are:

wherein R8 and R9 are independently methyl or hydrogen and R10 is lower alkyl or (CH2)n COOT" wherein n is 2 to 4 and R" is lower alkyl, provided that if two substituents R8 are present in the same molecule, at least one of them is hydrogen; or R, and Y together with their linking carbon atoms and nitrogen atom form a piperidine ring; R3 is hydrogen, lower alkyl, phenyl, lower alkylphenyl, halophenyl, lower alkoxyphenyl or dihalophenyl; and either R4 is lower alkyl and R5 is lower alkyl or lower alkoxycarbonyl or R4 and R5 together with the carbon atoms to which they are attached form a benzene ring which may bear lower alkyl or lower alkoxy substituents

wherein Y, Z, R, and R2 have the meanings hereinbefore defined;

wherein Hal is halogen and Y, Z, R, and R2 have the meanings hereinbefore defined: or

wherein Y, Z, R, and R2 have the meanings hereinbefore defined.

By the terms "lower alkyl" and "lower alkoxy" we mean alkyl and alkoxy radicals respectively containing from I to 4 carbon atoms.

As examples of dyestuffs which can be prepared by the process of the invention we mention, in particular, the dyestuffs of formula (a) wherein T and E are nitro, Y, K, G & J are hydrogen, Z is acetylamino and R, and R2 are both ethyl; the dyestuff of formula (a) wherein T, Y, K, G, J and Z are all hydrogen, E is nitro and R, and R2 are both ,-acetoxyethyl; and the dyestuffs of formula (a) wherein T is cyano, E is nitro, Y, K, G & J are hydrogen, Z is acetylamino and R, and R2 are both ethyl.

Dyestuffs of the formula (a) wherein T is cyano can be prepared from the equivalent dihalo dyestuff by the process of the invention.

The exchange of cyanide for halogen becomes progressively more difficult from the iodo through to the chloro dyestuff. Exchange of cyanide for iodide is especially favourable and rapid but the starting dyes are of course expensive.

Exchange of cyanide for chloride is markedly slower and unless partial conversion only is required, it is preferable to use elevated reaction temperatures and a stoichiometric rather than catalytic quantity (with respect to the dye) of the copper compound. Alternatively the use of a nitrogenous base with the phase transfer catalyst may be advantageous in this case.

In general, the reaction rate is not sensitive to other substituents, although it is rather slower if the radical B contains an alkyl group ortho to the azo link. It is especially rapid, however, if the radical B contains an acylamino group in the ortho position to the azo link.

The process of the invention is simply carried out by stirring the dye which is to be converted to the cyano derivative together with the phase transfer catalyst in a solvent, or in aqueous medium optionally in the presence of a water-immiscible solvent, and adding the pre-formed mixture of the copper compound and alkali metal or alkaline earth metal cyanide, at a temperature of from 15"C to 100 C.

However, if desired, temperatures of up to 1500C may be used to further increase the reaction rate. Agitation is continued for any time between 0.25 to 20 hours, usually between 1 to 5 hours, but again this will depend on the structure of the particular product involved. Preferably the mixture is added gradually as the reaction progresses to minimise any degradation of the azo dyestuff by high concentrations of cyanide ions. When the reaction is carried out in aqueous suspension the agitation is preferably vigorous, and since the rate of reaction will depend inter alia on the particle size of the reactants it is sometimes advantageous to subject the reactants to mild grinding during reaction for instance by agitating the reaction mixture in the presence of glass beads. A water-immiscible solvent may be used in addition to or instead of the grinding process.

When reaction is to be carried out without addition of water, it suffices however to add the copper catalyst and metal cyanide separately to the reaction mixture before heating commences.

The amount of the pre-formed mixture used will normally be such as to provide sufficient cyanide radicals for replacement of all of the halogen atoms. If, however, a mixture of dyes is to be produced by replacing only part of the replaceable halogens by cyano, then obviously the amount of the mixture used will be reduced accordingly.

The phase transfer catalyst will usually be present in the quantity of from 0.1 to 25% of the weight of the dye, preferably from 1 to 12%.

Aldehydes may be added to further catalyse the reaction. This is particularly advantageous where the copper usage is low. Lower aliphatic aldehydes are preferred especially formaldehyde.

Large amounts of aldehyde may be used but in general 0.05 to 0.5 moles/mole of halogen to be replaced give best results.

The dyes manufactured by the process of the invention can be applied to textile materials by any conventional method. Thus disperse dyes in the form of aqueous dispersions can be applied by dyeing, padding or printing processes using the conditions and other additives which are conventionally used, that is at temperatures of from 110"C to 1400C for 0.5 to 2 hours optionally in the presence of dispersing agents. Alternatively the dyes can be applied by solvent methods, for example by applying to the material a solution or dispersion of the dye in a suitable solvent optionally containing a minor amount of water at elevated temperature.

The invention is illustrated by the following examples in which parts and percentages are by weight.

Example 1 4.79 Parts of the dyestuff of formula (VII) in which X is bromo, 30 parts of water, 6 parts of anisole, and 0.5 parts of perhydrodibenzo-18-crown-6 are stirred together and heated under reflux (95"C) and a solution of 0.1 part of cuprous cyanide and 0.75 parts of potassium cyanide in 5 parts of water is added dropwise during 7 hours. After heating for 1 hour further, the anisole is removed by steam distillation and the dyestuff of formula (VII) in which X is cyano is collected by filtration and washed with water. The yield is 90% of the theoretical yield.

Example 2 4.79 Parts of the dyestuff of formula VII in which X is bromo, 0.5 parts of sodium cyanide, 0.1 parts of cuprous cyanide, 0.5 parts of octyl tributyl ammonium bromide and 30 parts of anisole are stirred and heated at 90100 C for 6 hours, when it is found by thin layer chromatography that conversion to the dyestuff of formula VII in which X is cyano is greater than 96%. The dyestuff is isolated by filtration of the cooled reaction mixture, or optionally by distillation or steam distillation of the solvent.

A similar result is obtained if the tetrabutyl ammonium bromide is replaced by an equal weight of 1 8-crown-6 and the amount of sodium cyanide is increased to 1.0 parts.

Example 3 5.8 Parts of the dyestuff of formula VIII in which T and L are both bromo groups, 30 parts of water, 13 parts of anisole and 0.5 parts of cetyl trimethyl ammonium bromide are stirred together and heated under reflux at 95". A solution prepared by dissolving 0.30 parts of cuprous cyanide and 0.29 parts of sodium cyanide in 3 parts of water is added dropwise during 1.5 hours. When this addition is complete a solution prepared by dissolving 0.69 parts of sodium cyanide in 7 parts of water is added dropwise during 3.5 hours. Stirring and heating is continued for a further 2 hours, and then steam is passed through the mixture to remove and recover the anisole.The residual aqueous suspension of dyestuff of formula VIII in which T and L are both cyano groups is cooled and stirred for 5 hours with 2.5 parts of ammonium persulphate, and the dyestuff is collected by filtration and washed with water. The yield is 86% and it is shown by thin layer chromatography that the dyestuff is exceptionally free of coloured impurities.

For the purpose of comparison the reaction is repeated with the difference that the cuprous cyanide is not dissolved in the sodium cyanide solution, but is added to the other ingredients before addition of the sodium cyanide solutions takes place. Reaction takes a similar course except that the product contains about 5% of a dull violet impurity.

Example 4 95.8 Parts of the dyestuff of formula VII in which X is bromo, in the form of a filter paste containing 238 parts of water, is mixed with 9.3 parts of cetyl trimethyl ammonium bromide, 140 parts of water, and 154 parts of anisole and the mixture is stirred and heated under reflux for 30 minutes. A solution prepared by dissolving 12.2 parts of sodium cyanide and 1.79 parts of cuprous cyanide in 100 parts of water is then added evenly during 3 hours, and stirring and heating is continued for 1.5 hours after the addition is finished. It is shown by thin layer chromatography that conversion to the dyestuff of formula VII in which X is cyano is complete. The anisole is removed and recovered by distillation in steam, and the precipitated dyestuff is collected by filtration of the residual aqueous suspension.It is then stirred for 4 hours with 450 parts of 14% aqueous ammonia solution to remove copper salts and minor impurities which are soluble in alkali, collected and washed with water. The yield of cyano dyestuff, which is outstandingly free of coloured impurities, is greater than 95% and after drying it contains 0.27% of copper.

Example 5 Example 4 is repeated with the differences that only 0.179 parts of cuprous cyanide are used and that the addition of sodium cyanide/cyanocuprate solution is made during 3.5 hours. The cyano dyestuff contains about 5% of unconverted starting material but otherwise is free from coloured impurities and contains only 0.085% of copper.

Optionally the cuprous cyanide may be replaced by an equivalent amount of cuprous chloride or cuprous bromide, with a corresponding small increase in the amount of sodium cyanide used.

In like manner the following dyestuffs may be prepared, each from the corresponding dyestuff containing a bromo group in place of the cyano group ortho to the azo link. After each is shown the shade of the dyestuff in dimethyl formamide solution.

Example Dyestuff Shade

Reddish-blue blue Reddish-blue Reddish-blue blue Greenish-blue blue Reddish-blue Greenish-blue Bluish-red Reddish-blue Example Dyestuff Shade

Bluish-red Greenish-blue blue Yellowish-red Yellowish-red red Yellowish-red Bluish-red ruby red blue Example Dyestuff Shade

blue violet blue Greenish-blue Greenish-blue reddish-blue blue red violet red blue-green Example Dyestuff Shade

greenish-blue blue reddish-blue blue blue violet blue blue-green violet Further examples of dyestuffs containing two cyano groups in positions ortho to the azo group, which may be prepared from the corresponding dyestuffs containing bromo groups are listed in the following Table. After each is shown the shade of its solution in dimethyl formamide.

Example Dyestuff Shade

red blue violet reddish-blue greenish-blue bluish-red violet bluish-red violet blue blue Example 59 The dyestuff of formula VII in which X is bromo (52.8 parts of dried nutsche paste of 90.7% strength), cetyl trimethyl ammonium bromide (4.7 parts), water (245 parts), anisole (77 parts) and formaldehyde (0.76 parts of 37 O aqueous solution) are stirred and heated to 80" and the pH is adjusted to between 6.5 and 7.0. The mixture is then heated to 95"C under reflux and a solution prepared by dissolving sodium cyanide (4.85 parts) and cuprous cyanide (0.090 parts) in water (45 parts) is run in evenly during 2 hours. After heating for a further hour. the anisole is removed by distillation in steam and the dyestuff is collected and dried.The yield of dyestuff of formula VII in which X is cyano is accurately determined from the extinction coefficient of the dried product, and found to be 88.46 of theoretical.

The experiment is repeated, but without addition of formaldehyde. The yield is 81.5% of theoretical.

WHAT WE CLAIM IS: 1. A process for the manufacture of azo dyes of the formula: D-A-N=N-B wherein A is an aromatic radical, B is an N-substituted p-aminophenyl radical and D, which is ortho to the azo group, is a cyano radical, which comprises reacting in a liquid medium in the presence of a phase transfer catalyst an azo dye of the same formula except that D is an iodine, bromine, or chlorine atom with a pre-formed mixture of a copper compound and an alkali metal cyanide or alkaline earth metal cyanide, there being insufficient of the copper compound present to complex with all of the metal cyanide.

2. A process as claimed in claim 1 in which the reaction is carried out in aqueous medium.

3. A process as claimed in claim 2 in which the azo dye is free from watersolubilising groups.

4. A process as claimed in any one of the preceding claims in which the phase transfer catalyst is a quaternary ammonium or phosphonium salt having the respective formulae:

wherein R, R', R" and R"', which may be the same or different, are alkyl, hydroxyalkyl, aryl, aralkyl or cycloalkenyl groups, or any two of R, R', R", R"' may together form a ring system containing 5-7 carbon atoms, and X- is an anion.

5. A process as claimed in claim 4 in which the quaternary ammonium or phosphonium salt contains more than 10 but not more than 70 carbon atoms per positively charged atom in each molecule.

6. A process as claimed in claim 4 in which the quaternary ammonium or phosphonium salt contains between 16 and 40 carbon atoms per positively charged atom in each molecule.

7. A process as claimed in any one of claims 1 to 3 in which the phase transfer catalyst is a cation complexing agent.

8. A process as claimed in claim 7 in which the cation complexing agent is a crown ether.

9. A process as claimed in claim 2 in which the phase transfer catalyst is a crown ether which bears one or more hydrophobic substituents.

10. A process as claimed in claims 2 or 3 in which there is a water-immiscible solvent.

11. A process as claimed in claim 10 in which the solvent is anisole, acetophenone or nitrobenzene.

12. A process as claimed in any one of the preceding claims in which the copper compound is a cuprous compound.

13. A process as claimed in any one of the preceding claims in which the cyanide is sodium or potassium cyanide.

14. A process as claimed in any one of the preceding claims in which the amount of copper compound used is upwards of 0.005 moles of copper/mole of replaceable halogen in the starting dye.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Example 59 The dyestuff of formula VII in which X is bromo (52.8 parts of dried nutsche paste of 90.7% strength), cetyl trimethyl ammonium bromide (4.7 parts), water (245 parts), anisole (77 parts) and formaldehyde (0.76 parts of 37 O aqueous solution) are stirred and heated to 80" and the pH is adjusted to between 6.5 and 7.0. The mixture is then heated to 95"C under reflux and a solution prepared by dissolving sodium cyanide (4.85 parts) and cuprous cyanide (0.090 parts) in water (45 parts) is run in evenly during 2 hours. After heating for a further hour. the anisole is removed by distillation in steam and the dyestuff is collected and dried.The yield of dyestuff of formula VII in which X is cyano is accurately determined from the extinction coefficient of the dried product, and found to be 88.46 of theoretical. The experiment is repeated, but without addition of formaldehyde. The yield is 81.5% of theoretical. WHAT WE CLAIM IS:

1. A process for the manufacture of azo dyes of the formula: D-A-N=N-B wherein A is an aromatic radical, B is an N-substituted p-aminophenyl radical and D, which is ortho to the azo group, is a cyano radical, which comprises reacting in a liquid medium in the presence of a phase transfer catalyst an azo dye of the same formula except that D is an iodine, bromine, or chlorine atom with a pre-formed mixture of a copper compound and an alkali metal cyanide or alkaline earth metal cyanide, there being insufficient of the copper compound present to complex with all of the metal cyanide.

15. A process as claimed in any one of the preceding claims in which the

preformed mixture is prepared by dissolving from 0.01 to 0.1 moles of the copper compound in 0.99 to 0.90 moles pro rata of the metal cyanide.

16. A process as claimed in any one of the preceding claims in which the radical A is a phenyl radical.

17. A process as claimed in any one of claims 1 to 5 in which the radical A is a benzoisothiazolyl-1 ,2 or 2,1-radical.

18. A process as claimed in any one of claims 1 to 15 in which the radical A is a naphthyl or quinolyl radical.

19. A process as claimed in any one of claims 1 to 15 in which the manufactured azo dye has the formula:

wherein T is hydrogen, lower alkyl, lower alkoxy, cyano, halogen, nitro, lower alkyl sulphonyl, lower alkylsulphonamido or a radical of the formula:

E is hydrogen, lower alkyl, lower alkoxy, lower alkyl carbonyl, cyano, lower alkoxy carbonyl, trifluoromethyl, acylamino, halogen, optionally substituted phenylazo or nitro; G is hydrogen or nitro; J is hydrogen or nitro; Y is hydrogen, lower alkyl, lower alkoxy or halogen; Z is hydrogen, lower alkyl, lower alkoxy, halogen or acylamino; K is hydrogen; or Z and K together with the carbon atoms to which they are attached form a benzene ring which bears a sulphonic acid group or alkali metal salt thereof: R, is lower alkyl, hydroxy lower alkyl, lower alkoxy lower alkyl, lower alkoxy carbonyl lower alkyl, cyano lower alkyl, and phenyl lower alkyl, cyclohexyl or phenyl; R2 is hydrogen, lower alkyl, hydroxy lower alkyl, lower alkoxy lower alkyl, lower alkoxy carbonyl lower alkyl or lower alkyl carrying a pyridinium salt, or either or both R, and R2 are

wherein R8 and Rg are independently methyl or hydrogen and Ranis lower alkyl or (CH2)n COOR,1 wherein n is 2 to 4 and R1, is lower alkyl, provided that if two substituents R8 are present in the same molecule, at least one of them is hydrogen: or R1 and Y together with their linking carbon atoms and nitrogen atom form a piperidine ring; R3 is hydrogen, lower alkyl, phenyl, lower alkylphenyl, halophenyl, lower alkoxyphenyl or dihalophenyl: and either R4 is lower alkyl and R5 is lower alkoxycarbonyl or R4 and Rs together with the carbon atoms to which they are attached form a benzene ring which may bear lower alkyl or lower alkoxy substituents.

20. A process as claimed in any one of claims 1 to 15 in which the manufactured azo dye has the formula:

wherein Y, Z, R, and R2 have the meanings given in claim 19.

21. A process as claimed in any one of claims 1 to 15 in which the manufactured azo dye has one of the formulae:

wherein Hal is halogen and Y, Z, R, and R2 have the meanings given in claim 19.

22. A process as claimed in claim 19 wherein E is nitro; T is hydrogen, nitro or cyano; Z is acylamino; and R, and R2 are both lower alkyl or lower alkoxy carbonyl lower alkyl.

23. A process as claimed in any one of the preceding claims in which the reaction is carried out at a temperature of from 15 to 1000C.

24. A process as claimed in any one of the preceding claims in which the amount of the preformed mixture used is such as to provide sufficient cyanide radicals for replacement of all the halogen atoms on the starting dye.

25. A process as claimed in any one of the preceding claims in which the phase transfer catalyst is present in the quantity of from 0.1 to 25% of the weight of the dye.

26. A process as claimed in any one of claims 1 to 24 in which the phase transfer catalyst is present in the quantity of from 1 to 12"; of the weight of the dye.

27. A process as claimed in any one of the preceding claims in which an aldehyde is added to the reaction mixture.

28. A process as claimed in claim 27 in which the aldehyde is a lower aliphatic aldehyde.

29. A process as claimed in claim 28 in which the aldehyde is formaldehyde.

30. A process as claimed in any one of claims 27 to 29 in which the amount of aldehyde used is in the range of 0.05 to 0.5 moles/mole of halogen to be replaced on the starting dye.

31. A process as claimed in claim I substantially as herein described with reference to any one of Examples I to 58.

32. A process as claimed in claim 1 substantially as herein described with reference to Example 59.

33. Dyestuffs whenever produced by a process as claimed in any one of claims I to 31.

34. A process for dyeing textile materials which comprises applying a dyestuff as claimed in claim 33 to a textile material by any conventional dyeing method.

35. Textile materials whenever dyed by a process as claimed in claim 34.